RISC-V Fixes for 5.9-rc6 (or shortly after)

* A fix for a lockdep issue to avoid an asserting triggering during early boot.
   There shouldn't be any incorrect behavior as the system isn't concurrent at
   the time.
 * The addition of a missing fence when installing early fixmap mappings.
 * A corretion to the K210 device tree's interrupt map.
 * A fix for M-mode timer handling on the K210.
 
 I know it's a it of an odd time, so if these don't make rc6 it's not a big
 deal, but I thought I'd just send it out now rather that waiting as these are
 ready to go.
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Merge tag 'riscv-for-linus-5.9-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux

Pull RISC-V fixes from Palmer Dabbelt:

 - A fix for a lockdep issue to avoid an asserting triggering during
   early boot. There shouldn't be any incorrect behavior as the system
   isn't concurrent at the time.

 - The addition of a missing fence when installing early fixmap
   mappings.

 - A corretion to the K210 device tree's interrupt map.

 - A fix for M-mode timer handling on the K210.

* tag 'riscv-for-linus-5.9-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux:
  RISC-V: Resurrect the MMIO timer implementation for M-mode systems
  riscv: Fix Kendryte K210 device tree
  riscv: Add sfence.vma after early page table changes
  RISC-V: Take text_mutex in ftrace_init_nop()

arch/riscv/Kconfig

@@ -32,6 +32,7 @@ config RISCV
 	select ARCH_WANT_FRAME_POINTERS
 	select ARCH_WANT_HUGE_PMD_SHARE if 64BIT
 	select CLONE_BACKWARDS
+	select CLINT_TIMER if !MMU
 	select COMMON_CLK
 	select EDAC_SUPPORT
 	select GENERIC_ARCH_TOPOLOGY if SMP

arch/riscv/boot/dts/kendryte/k210.dtsi

@@ -95,10 +95,12 @@
 			#clock-cells = <1>;
 		};
 
-		clint0: interrupt-controller@2000000 {
+		clint0: clint@2000000 {
+			#interrupt-cells = <1>;
 			compatible = "riscv,clint0";
 			reg = <0x2000000 0xC000>;
-			interrupts-extended = <&cpu0_intc 3>,  <&cpu1_intc 3>;
+			interrupts-extended =  <&cpu0_intc 3 &cpu0_intc 7
+						&cpu1_intc 3 &cpu1_intc 7>;
 			clocks = <&sysctl K210_CLK_ACLK>;
 		};
 

arch/riscv/include/asm/clint.h

@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2020 Google, Inc
+ */
+
+#ifndef _ASM_RISCV_CLINT_H
+#define _ASM_RISCV_CLINT_H
+
+#include <linux/types.h>
+#include <asm/mmio.h>
+
+#ifdef CONFIG_RISCV_M_MODE
+/*
+ * This lives in the CLINT driver, but is accessed directly by timex.h to avoid
+ * any overhead when accessing the MMIO timer.
+ *
+ * The ISA defines mtime as a 64-bit memory-mapped register that increments at
+ * a constant frequency, but it doesn't define some other constraints we depend
+ * on (most notably ordering constraints, but also some simpler stuff like the
+ * memory layout).  Thus, this is called "clint_time_val" instead of something
+ * like "riscv_mtime", to signify that these non-ISA assumptions must hold.
+ */
+extern u64 __iomem *clint_time_val;
+#endif
+
+#endif

arch/riscv/include/asm/ftrace.h

@@ -66,6 +66,13 @@ do {									\
  * Let auipc+jalr be the basic *mcount unit*, so we make it 8 bytes here.
  */
 #define MCOUNT_INSN_SIZE 8
+
+#ifndef __ASSEMBLY__
+struct dyn_ftrace;
+int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
+#define ftrace_init_nop ftrace_init_nop
+#endif
+
 #endif
 
 #endif /* _ASM_RISCV_FTRACE_H */

arch/riscv/include/asm/timex.h

@@ -10,6 +10,31 @@
 
 typedef unsigned long cycles_t;
 
+#ifdef CONFIG_RISCV_M_MODE
+
+#include <asm/clint.h>
+
+#ifdef CONFIG_64BIT
+static inline cycles_t get_cycles(void)
+{
+	return readq_relaxed(clint_time_val);
+}
+#else /* !CONFIG_64BIT */
+static inline u32 get_cycles(void)
+{
+	return readl_relaxed(((u32 *)clint_time_val));
+}
+#define get_cycles get_cycles
+
+static inline u32 get_cycles_hi(void)
+{
+	return readl_relaxed(((u32 *)clint_time_val) + 1);
+}
+#define get_cycles_hi get_cycles_hi
+#endif /* CONFIG_64BIT */
+
+#else /* CONFIG_RISCV_M_MODE */
+
 static inline cycles_t get_cycles(void)
 {
 	return csr_read(CSR_TIME);
@@ -41,6 +66,8 @@ static inline u64 get_cycles64(void)
 }
 #endif /* CONFIG_64BIT */
 
+#endif /* !CONFIG_RISCV_M_MODE */
+
 #define ARCH_HAS_READ_CURRENT_TIMER
 static inline int read_current_timer(unsigned long *timer_val)
 {

arch/riscv/kernel/ftrace.c

@@ -97,6 +97,25 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
 	return __ftrace_modify_call(rec->ip, addr, false);
 }
 
+
+/*
+ * This is called early on, and isn't wrapped by
+ * ftrace_arch_code_modify_{prepare,post_process}() and therefor doesn't hold
+ * text_mutex, which triggers a lockdep failure.  SMP isn't running so we could
+ * just directly poke the text, but it's simpler to just take the lock
+ * ourselves.
+ */
+int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
+{
+	int out;
+
+	ftrace_arch_code_modify_prepare();
+	out = ftrace_make_nop(mod, rec, MCOUNT_ADDR);
+	ftrace_arch_code_modify_post_process();
+
+	return out;
+}
+
 int ftrace_update_ftrace_func(ftrace_func_t func)
 {
 	int ret = __ftrace_modify_call((unsigned long)&ftrace_call,

arch/riscv/mm/init.c

@@ -226,12 +226,11 @@ void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
 
 	ptep = &fixmap_pte[pte_index(addr)];
 
-	if (pgprot_val(prot)) {
+	if (pgprot_val(prot))
 		set_pte(ptep, pfn_pte(phys >> PAGE_SHIFT, prot));
-	} else {
+	else
 		pte_clear(&init_mm, addr, ptep);
-		local_flush_tlb_page(addr);
-	}
+	local_flush_tlb_page(addr);
 }
 
 static pte_t *__init get_pte_virt(phys_addr_t pa)

drivers/clocksource/timer-clint.c

@@ -19,6 +19,11 @@
 #include <linux/interrupt.h>
 #include <linux/of_irq.h>
 #include <linux/smp.h>
+#include <linux/timex.h>
+
+#ifndef CONFIG_RISCV_M_MODE
+#include <asm/clint.h>
+#endif
 
 #define CLINT_IPI_OFF		0
 #define CLINT_TIMER_CMP_OFF	0x4000
@@ -31,6 +36,10 @@ static u64 __iomem *clint_timer_val;
 static unsigned long clint_timer_freq;
 static unsigned int clint_timer_irq;
 
+#ifdef CONFIG_RISCV_M_MODE
+u64 __iomem *clint_time_val;
+#endif
+
 static void clint_send_ipi(const struct cpumask *target)
 {
 	unsigned int cpu;
@@ -184,6 +193,14 @@ static int __init clint_timer_init_dt(struct device_node *np)
 	clint_timer_val = base + CLINT_TIMER_VAL_OFF;
 	clint_timer_freq = riscv_timebase;
 
+#ifdef CONFIG_RISCV_M_MODE
+	/*
+	 * Yes, that's an odd naming scheme.  time_val is public, but hopefully
+	 * will die in favor of something cleaner.
+	 */
+	clint_time_val = clint_timer_val;
+#endif
+
 	pr_info("%pOFP: timer running at %ld Hz\n", np, clint_timer_freq);
 
 	rc = clocksource_register_hz(&clint_clocksource, clint_timer_freq);