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![Catalin Marinas](/assets/img/avatar_default.png)
This CPU generates synchronous VFP exceptions in a non-standard way - the FPEXC.EX bit set but without the FPSCR.IXE bit being set like in the VFP subarchitecture 1 or just the FPEXC.DEX bit like in VFP subarchitecture 2. The main problem is that the faulty instruction (which needs to be emulated in software) will be restarted several times (normally until a context switch disables the VFP). This patch ensures that the VFP exception is treated as synchronous. Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Cc: Nicolas Pitre <nico@cam.org>
508 lines
12 KiB
C
508 lines
12 KiB
C
/*
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* linux/arch/arm/vfp/vfpmodule.c
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*
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* Copyright (C) 2004 ARM Limited.
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* Written by Deep Blue Solutions Limited.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/signal.h>
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#include <linux/sched.h>
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#include <linux/init.h>
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#include <asm/thread_notify.h>
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#include <asm/vfp.h>
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#include "vfpinstr.h"
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#include "vfp.h"
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/*
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* Our undef handlers (in entry.S)
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*/
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void vfp_testing_entry(void);
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void vfp_support_entry(void);
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void vfp_null_entry(void);
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void (*vfp_vector)(void) = vfp_null_entry;
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union vfp_state *last_VFP_context[NR_CPUS];
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/*
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* Dual-use variable.
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* Used in startup: set to non-zero if VFP checks fail
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* After startup, holds VFP architecture
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*/
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unsigned int VFP_arch;
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static int vfp_notifier(struct notifier_block *self, unsigned long cmd, void *v)
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{
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struct thread_info *thread = v;
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union vfp_state *vfp;
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__u32 cpu = thread->cpu;
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if (likely(cmd == THREAD_NOTIFY_SWITCH)) {
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u32 fpexc = fmrx(FPEXC);
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#ifdef CONFIG_SMP
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/*
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* On SMP, if VFP is enabled, save the old state in
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* case the thread migrates to a different CPU. The
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* restoring is done lazily.
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*/
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if ((fpexc & FPEXC_EN) && last_VFP_context[cpu]) {
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vfp_save_state(last_VFP_context[cpu], fpexc);
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last_VFP_context[cpu]->hard.cpu = cpu;
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}
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/*
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* Thread migration, just force the reloading of the
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* state on the new CPU in case the VFP registers
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* contain stale data.
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*/
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if (thread->vfpstate.hard.cpu != cpu)
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last_VFP_context[cpu] = NULL;
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#endif
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/*
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* Always disable VFP so we can lazily save/restore the
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* old state.
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*/
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fmxr(FPEXC, fpexc & ~FPEXC_EN);
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return NOTIFY_DONE;
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}
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vfp = &thread->vfpstate;
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if (cmd == THREAD_NOTIFY_FLUSH) {
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/*
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* Per-thread VFP initialisation.
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*/
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memset(vfp, 0, sizeof(union vfp_state));
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vfp->hard.fpexc = FPEXC_EN;
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vfp->hard.fpscr = FPSCR_ROUND_NEAREST;
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/*
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* Disable VFP to ensure we initialise it first.
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*/
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fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
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}
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/* flush and release case: Per-thread VFP cleanup. */
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if (last_VFP_context[cpu] == vfp)
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last_VFP_context[cpu] = NULL;
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return NOTIFY_DONE;
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}
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static struct notifier_block vfp_notifier_block = {
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.notifier_call = vfp_notifier,
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};
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/*
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* Raise a SIGFPE for the current process.
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* sicode describes the signal being raised.
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*/
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void vfp_raise_sigfpe(unsigned int sicode, struct pt_regs *regs)
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{
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siginfo_t info;
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memset(&info, 0, sizeof(info));
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info.si_signo = SIGFPE;
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info.si_code = sicode;
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info.si_addr = (void __user *)(instruction_pointer(regs) - 4);
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/*
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* This is the same as NWFPE, because it's not clear what
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* this is used for
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*/
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current->thread.error_code = 0;
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current->thread.trap_no = 6;
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send_sig_info(SIGFPE, &info, current);
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}
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static void vfp_panic(char *reason, u32 inst)
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{
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int i;
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printk(KERN_ERR "VFP: Error: %s\n", reason);
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printk(KERN_ERR "VFP: EXC 0x%08x SCR 0x%08x INST 0x%08x\n",
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fmrx(FPEXC), fmrx(FPSCR), inst);
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for (i = 0; i < 32; i += 2)
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printk(KERN_ERR "VFP: s%2u: 0x%08x s%2u: 0x%08x\n",
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i, vfp_get_float(i), i+1, vfp_get_float(i+1));
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}
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/*
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* Process bitmask of exception conditions.
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*/
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static void vfp_raise_exceptions(u32 exceptions, u32 inst, u32 fpscr, struct pt_regs *regs)
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{
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int si_code = 0;
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pr_debug("VFP: raising exceptions %08x\n", exceptions);
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if (exceptions == VFP_EXCEPTION_ERROR) {
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vfp_panic("unhandled bounce", inst);
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vfp_raise_sigfpe(0, regs);
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return;
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}
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/*
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* Update the FPSCR with the additional exception flags.
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* Comparison instructions always return at least one of
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* these flags set.
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*/
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fpscr |= exceptions;
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fmxr(FPSCR, fpscr);
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#define RAISE(stat,en,sig) \
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if (exceptions & stat && fpscr & en) \
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si_code = sig;
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/*
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* These are arranged in priority order, least to highest.
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*/
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RAISE(FPSCR_DZC, FPSCR_DZE, FPE_FLTDIV);
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RAISE(FPSCR_IXC, FPSCR_IXE, FPE_FLTRES);
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RAISE(FPSCR_UFC, FPSCR_UFE, FPE_FLTUND);
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RAISE(FPSCR_OFC, FPSCR_OFE, FPE_FLTOVF);
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RAISE(FPSCR_IOC, FPSCR_IOE, FPE_FLTINV);
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if (si_code)
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vfp_raise_sigfpe(si_code, regs);
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}
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/*
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* Emulate a VFP instruction.
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*/
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static u32 vfp_emulate_instruction(u32 inst, u32 fpscr, struct pt_regs *regs)
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{
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u32 exceptions = VFP_EXCEPTION_ERROR;
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pr_debug("VFP: emulate: INST=0x%08x SCR=0x%08x\n", inst, fpscr);
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if (INST_CPRTDO(inst)) {
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if (!INST_CPRT(inst)) {
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/*
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* CPDO
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*/
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if (vfp_single(inst)) {
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exceptions = vfp_single_cpdo(inst, fpscr);
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} else {
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exceptions = vfp_double_cpdo(inst, fpscr);
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}
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} else {
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/*
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* A CPRT instruction can not appear in FPINST2, nor
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* can it cause an exception. Therefore, we do not
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* have to emulate it.
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*/
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}
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} else {
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/*
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* A CPDT instruction can not appear in FPINST2, nor can
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* it cause an exception. Therefore, we do not have to
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* emulate it.
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*/
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}
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return exceptions & ~VFP_NAN_FLAG;
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}
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/*
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* Package up a bounce condition.
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*/
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void VFP_bounce(u32 trigger, u32 fpexc, struct pt_regs *regs)
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{
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u32 fpscr, orig_fpscr, fpsid, exceptions;
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pr_debug("VFP: bounce: trigger %08x fpexc %08x\n", trigger, fpexc);
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/*
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* At this point, FPEXC can have the following configuration:
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*
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* EX DEX IXE
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* 0 1 x - synchronous exception
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* 1 x 0 - asynchronous exception
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* 1 x 1 - sychronous on VFP subarch 1 and asynchronous on later
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* 0 0 1 - synchronous on VFP9 (non-standard subarch 1
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* implementation), undefined otherwise
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*
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* Clear various bits and enable access to the VFP so we can
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* handle the bounce.
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*/
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fmxr(FPEXC, fpexc & ~(FPEXC_EX|FPEXC_DEX|FPEXC_FP2V|FPEXC_VV|FPEXC_TRAP_MASK));
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fpsid = fmrx(FPSID);
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orig_fpscr = fpscr = fmrx(FPSCR);
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/*
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* Check for the special VFP subarch 1 and FPSCR.IXE bit case
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*/
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if ((fpsid & FPSID_ARCH_MASK) == (1 << FPSID_ARCH_BIT)
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&& (fpscr & FPSCR_IXE)) {
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/*
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* Synchronous exception, emulate the trigger instruction
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*/
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goto emulate;
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}
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if (fpexc & FPEXC_EX) {
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#ifndef CONFIG_CPU_FEROCEON
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/*
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* Asynchronous exception. The instruction is read from FPINST
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* and the interrupted instruction has to be restarted.
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*/
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trigger = fmrx(FPINST);
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regs->ARM_pc -= 4;
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#endif
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} else if (!(fpexc & FPEXC_DEX)) {
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/*
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* Illegal combination of bits. It can be caused by an
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* unallocated VFP instruction but with FPSCR.IXE set and not
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* on VFP subarch 1.
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*/
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vfp_raise_exceptions(VFP_EXCEPTION_ERROR, trigger, fpscr, regs);
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goto exit;
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}
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/*
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* Modify fpscr to indicate the number of iterations remaining.
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* If FPEXC.EX is 0, FPEXC.DEX is 1 and the FPEXC.VV bit indicates
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* whether FPEXC.VECITR or FPSCR.LEN is used.
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*/
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if (fpexc & (FPEXC_EX | FPEXC_VV)) {
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u32 len;
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len = fpexc + (1 << FPEXC_LENGTH_BIT);
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fpscr &= ~FPSCR_LENGTH_MASK;
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fpscr |= (len & FPEXC_LENGTH_MASK) << (FPSCR_LENGTH_BIT - FPEXC_LENGTH_BIT);
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}
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/*
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* Handle the first FP instruction. We used to take note of the
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* FPEXC bounce reason, but this appears to be unreliable.
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* Emulate the bounced instruction instead.
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*/
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exceptions = vfp_emulate_instruction(trigger, fpscr, regs);
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if (exceptions)
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vfp_raise_exceptions(exceptions, trigger, orig_fpscr, regs);
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/*
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* If there isn't a second FP instruction, exit now. Note that
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* the FPEXC.FP2V bit is valid only if FPEXC.EX is 1.
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*/
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if (fpexc ^ (FPEXC_EX | FPEXC_FP2V))
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goto exit;
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/*
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* The barrier() here prevents fpinst2 being read
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* before the condition above.
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*/
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barrier();
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trigger = fmrx(FPINST2);
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emulate:
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exceptions = vfp_emulate_instruction(trigger, orig_fpscr, regs);
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if (exceptions)
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vfp_raise_exceptions(exceptions, trigger, orig_fpscr, regs);
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exit:
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preempt_enable();
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}
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static void vfp_enable(void *unused)
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{
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u32 access = get_copro_access();
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/*
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* Enable full access to VFP (cp10 and cp11)
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*/
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set_copro_access(access | CPACC_FULL(10) | CPACC_FULL(11));
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}
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#ifdef CONFIG_PM
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#include <linux/sysdev.h>
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static int vfp_pm_suspend(struct sys_device *dev, pm_message_t state)
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{
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struct thread_info *ti = current_thread_info();
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u32 fpexc = fmrx(FPEXC);
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/* if vfp is on, then save state for resumption */
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if (fpexc & FPEXC_EN) {
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printk(KERN_DEBUG "%s: saving vfp state\n", __func__);
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vfp_save_state(&ti->vfpstate, fpexc);
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/* disable, just in case */
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fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
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}
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/* clear any information we had about last context state */
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memset(last_VFP_context, 0, sizeof(last_VFP_context));
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return 0;
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}
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static int vfp_pm_resume(struct sys_device *dev)
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{
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/* ensure we have access to the vfp */
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vfp_enable(NULL);
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/* and disable it to ensure the next usage restores the state */
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fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
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return 0;
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}
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static struct sysdev_class vfp_pm_sysclass = {
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.name = "vfp",
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.suspend = vfp_pm_suspend,
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.resume = vfp_pm_resume,
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};
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static struct sys_device vfp_pm_sysdev = {
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.cls = &vfp_pm_sysclass,
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};
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static void vfp_pm_init(void)
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{
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sysdev_class_register(&vfp_pm_sysclass);
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sysdev_register(&vfp_pm_sysdev);
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}
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#else
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static inline void vfp_pm_init(void) { }
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#endif /* CONFIG_PM */
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/*
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* Synchronise the hardware VFP state of a thread other than current with the
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* saved one. This function is used by the ptrace mechanism.
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*/
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#ifdef CONFIG_SMP
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void vfp_sync_state(struct thread_info *thread)
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{
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/*
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* On SMP systems, the VFP state is automatically saved at every
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* context switch. We mark the thread VFP state as belonging to a
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* non-existent CPU so that the saved one will be reloaded when
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* needed.
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*/
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thread->vfpstate.hard.cpu = NR_CPUS;
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}
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#else
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void vfp_sync_state(struct thread_info *thread)
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{
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unsigned int cpu = get_cpu();
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u32 fpexc = fmrx(FPEXC);
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/*
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* If VFP is enabled, the previous state was already saved and
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* last_VFP_context updated.
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*/
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if (fpexc & FPEXC_EN)
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goto out;
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if (!last_VFP_context[cpu])
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goto out;
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/*
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* Save the last VFP state on this CPU.
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*/
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fmxr(FPEXC, fpexc | FPEXC_EN);
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vfp_save_state(last_VFP_context[cpu], fpexc);
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fmxr(FPEXC, fpexc);
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/*
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* Set the context to NULL to force a reload the next time the thread
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* uses the VFP.
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*/
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last_VFP_context[cpu] = NULL;
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out:
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put_cpu();
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}
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#endif
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#include <linux/smp.h>
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/*
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* VFP support code initialisation.
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*/
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static int __init vfp_init(void)
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{
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unsigned int vfpsid;
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unsigned int cpu_arch = cpu_architecture();
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if (cpu_arch >= CPU_ARCH_ARMv6)
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vfp_enable(NULL);
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/*
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* First check that there is a VFP that we can use.
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* The handler is already setup to just log calls, so
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* we just need to read the VFPSID register.
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*/
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vfp_vector = vfp_testing_entry;
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barrier();
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vfpsid = fmrx(FPSID);
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barrier();
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vfp_vector = vfp_null_entry;
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printk(KERN_INFO "VFP support v0.3: ");
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if (VFP_arch)
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printk("not present\n");
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else if (vfpsid & FPSID_NODOUBLE) {
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printk("no double precision support\n");
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} else {
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smp_call_function(vfp_enable, NULL, 1);
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VFP_arch = (vfpsid & FPSID_ARCH_MASK) >> FPSID_ARCH_BIT; /* Extract the architecture version */
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printk("implementor %02x architecture %d part %02x variant %x rev %x\n",
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(vfpsid & FPSID_IMPLEMENTER_MASK) >> FPSID_IMPLEMENTER_BIT,
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(vfpsid & FPSID_ARCH_MASK) >> FPSID_ARCH_BIT,
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(vfpsid & FPSID_PART_MASK) >> FPSID_PART_BIT,
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(vfpsid & FPSID_VARIANT_MASK) >> FPSID_VARIANT_BIT,
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(vfpsid & FPSID_REV_MASK) >> FPSID_REV_BIT);
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vfp_vector = vfp_support_entry;
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thread_register_notifier(&vfp_notifier_block);
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vfp_pm_init();
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/*
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* We detected VFP, and the support code is
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* in place; report VFP support to userspace.
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*/
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elf_hwcap |= HWCAP_VFP;
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#ifdef CONFIG_VFPv3
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if (VFP_arch >= 3) {
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elf_hwcap |= HWCAP_VFPv3;
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/*
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* Check for VFPv3 D16. CPUs in this configuration
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* only have 16 x 64bit registers.
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*/
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if (((fmrx(MVFR0) & MVFR0_A_SIMD_MASK)) == 1)
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elf_hwcap |= HWCAP_VFPv3D16;
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}
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#endif
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#ifdef CONFIG_NEON
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/*
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* Check for the presence of the Advanced SIMD
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* load/store instructions, integer and single
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* precision floating point operations.
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*/
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if ((fmrx(MVFR1) & 0x000fff00) == 0x00011100)
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elf_hwcap |= HWCAP_NEON;
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#endif
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}
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return 0;
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}
|
|
|
|
late_initcall(vfp_init);
|