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![Linus Walleij](/assets/img/avatar_default.png)
The two drivers used for Ux500 sched_clock use two Kconfig symbols to select which of the two gets used as sched_clock. This isn't right: the workaround is trying to make sure that the NONSTOP timer is used for sched_clock in order to keep that clock ticking consistently over a suspend/resume cycle. (Otherwise sched_clock simply stops during suspend and continues after resume). This will notably affect any timetstamped debug prints, so that they show the absolute number of seconds since the system was booted and does not loose wall-clock time during suspend and resume as if time stood still. The real way to fix this problem is to make sched_clock take advantage of any NONSTOP clock source on the system and adjust accordingly, not to try to work around this by using a different sched_clock depending on what system we are compiling for. This can solve the problem for everyone instead of providing a local solution. Cc: Baolin Wang <baolin.wang@linaro.org> Signed-off-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
284 lines
7.4 KiB
C
284 lines
7.4 KiB
C
/*
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* Copyright (C) 2008 STMicroelectronics
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* Copyright (C) 2010 Alessandro Rubini
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* Copyright (C) 2010 Linus Walleij for ST-Ericsson
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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/init.h>
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#include <linux/interrupt.h>
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#include <linux/irq.h>
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#include <linux/io.h>
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#include <linux/clockchips.h>
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#include <linux/clocksource.h>
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#include <linux/of_address.h>
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#include <linux/of_irq.h>
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#include <linux/of_platform.h>
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#include <linux/clk.h>
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#include <linux/jiffies.h>
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#include <linux/delay.h>
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#include <linux/err.h>
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#include <linux/sched_clock.h>
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#include <asm/mach/time.h>
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/*
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* The MTU device hosts four different counters, with 4 set of
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* registers. These are register names.
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*/
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#define MTU_IMSC 0x00 /* Interrupt mask set/clear */
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#define MTU_RIS 0x04 /* Raw interrupt status */
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#define MTU_MIS 0x08 /* Masked interrupt status */
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#define MTU_ICR 0x0C /* Interrupt clear register */
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/* per-timer registers take 0..3 as argument */
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#define MTU_LR(x) (0x10 + 0x10 * (x) + 0x00) /* Load value */
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#define MTU_VAL(x) (0x10 + 0x10 * (x) + 0x04) /* Current value */
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#define MTU_CR(x) (0x10 + 0x10 * (x) + 0x08) /* Control reg */
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#define MTU_BGLR(x) (0x10 + 0x10 * (x) + 0x0c) /* At next overflow */
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/* bits for the control register */
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#define MTU_CRn_ENA 0x80
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#define MTU_CRn_PERIODIC 0x40 /* if 0 = free-running */
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#define MTU_CRn_PRESCALE_MASK 0x0c
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#define MTU_CRn_PRESCALE_1 0x00
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#define MTU_CRn_PRESCALE_16 0x04
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#define MTU_CRn_PRESCALE_256 0x08
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#define MTU_CRn_32BITS 0x02
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#define MTU_CRn_ONESHOT 0x01 /* if 0 = wraps reloading from BGLR*/
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/* Other registers are usual amba/primecell registers, currently not used */
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#define MTU_ITCR 0xff0
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#define MTU_ITOP 0xff4
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#define MTU_PERIPH_ID0 0xfe0
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#define MTU_PERIPH_ID1 0xfe4
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#define MTU_PERIPH_ID2 0xfe8
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#define MTU_PERIPH_ID3 0xfeC
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#define MTU_PCELL0 0xff0
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#define MTU_PCELL1 0xff4
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#define MTU_PCELL2 0xff8
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#define MTU_PCELL3 0xffC
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static void __iomem *mtu_base;
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static bool clkevt_periodic;
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static u32 clk_prescale;
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static u32 nmdk_cycle; /* write-once */
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static struct delay_timer mtu_delay_timer;
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/*
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* Override the global weak sched_clock symbol with this
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* local implementation which uses the clocksource to get some
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* better resolution when scheduling the kernel.
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*/
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static u64 notrace nomadik_read_sched_clock(void)
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{
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if (unlikely(!mtu_base))
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return 0;
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return -readl(mtu_base + MTU_VAL(0));
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}
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static unsigned long nmdk_timer_read_current_timer(void)
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{
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return ~readl_relaxed(mtu_base + MTU_VAL(0));
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}
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/* Clockevent device: use one-shot mode */
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static int nmdk_clkevt_next(unsigned long evt, struct clock_event_device *ev)
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{
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writel(1 << 1, mtu_base + MTU_IMSC);
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writel(evt, mtu_base + MTU_LR(1));
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/* Load highest value, enable device, enable interrupts */
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writel(MTU_CRn_ONESHOT | clk_prescale |
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MTU_CRn_32BITS | MTU_CRn_ENA,
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mtu_base + MTU_CR(1));
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return 0;
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}
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static void nmdk_clkevt_reset(void)
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{
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if (clkevt_periodic) {
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/* Timer: configure load and background-load, and fire it up */
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writel(nmdk_cycle, mtu_base + MTU_LR(1));
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writel(nmdk_cycle, mtu_base + MTU_BGLR(1));
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writel(MTU_CRn_PERIODIC | clk_prescale |
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MTU_CRn_32BITS | MTU_CRn_ENA,
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mtu_base + MTU_CR(1));
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writel(1 << 1, mtu_base + MTU_IMSC);
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} else {
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/* Generate an interrupt to start the clockevent again */
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(void) nmdk_clkevt_next(nmdk_cycle, NULL);
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}
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}
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static int nmdk_clkevt_shutdown(struct clock_event_device *evt)
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{
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writel(0, mtu_base + MTU_IMSC);
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/* disable timer */
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writel(0, mtu_base + MTU_CR(1));
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/* load some high default value */
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writel(0xffffffff, mtu_base + MTU_LR(1));
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return 0;
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}
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static int nmdk_clkevt_set_oneshot(struct clock_event_device *evt)
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{
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clkevt_periodic = false;
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return 0;
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}
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static int nmdk_clkevt_set_periodic(struct clock_event_device *evt)
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{
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clkevt_periodic = true;
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nmdk_clkevt_reset();
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return 0;
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}
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static void nmdk_clksrc_reset(void)
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{
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/* Disable */
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writel(0, mtu_base + MTU_CR(0));
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/* ClockSource: configure load and background-load, and fire it up */
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writel(nmdk_cycle, mtu_base + MTU_LR(0));
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writel(nmdk_cycle, mtu_base + MTU_BGLR(0));
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writel(clk_prescale | MTU_CRn_32BITS | MTU_CRn_ENA,
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mtu_base + MTU_CR(0));
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}
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static void nmdk_clkevt_resume(struct clock_event_device *cedev)
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{
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nmdk_clkevt_reset();
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nmdk_clksrc_reset();
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}
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static struct clock_event_device nmdk_clkevt = {
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.name = "mtu_1",
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.features = CLOCK_EVT_FEAT_ONESHOT |
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CLOCK_EVT_FEAT_PERIODIC |
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CLOCK_EVT_FEAT_DYNIRQ,
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.rating = 200,
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.set_state_shutdown = nmdk_clkevt_shutdown,
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.set_state_periodic = nmdk_clkevt_set_periodic,
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.set_state_oneshot = nmdk_clkevt_set_oneshot,
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.set_next_event = nmdk_clkevt_next,
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.resume = nmdk_clkevt_resume,
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};
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/*
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* IRQ Handler for timer 1 of the MTU block.
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*/
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static irqreturn_t nmdk_timer_interrupt(int irq, void *dev_id)
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{
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struct clock_event_device *evdev = dev_id;
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writel(1 << 1, mtu_base + MTU_ICR); /* Interrupt clear reg */
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evdev->event_handler(evdev);
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return IRQ_HANDLED;
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}
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static struct irqaction nmdk_timer_irq = {
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.name = "Nomadik Timer Tick",
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.flags = IRQF_TIMER,
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.handler = nmdk_timer_interrupt,
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.dev_id = &nmdk_clkevt,
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};
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static int __init nmdk_timer_init(void __iomem *base, int irq,
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struct clk *pclk, struct clk *clk)
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{
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unsigned long rate;
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int ret;
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mtu_base = base;
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BUG_ON(clk_prepare_enable(pclk));
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BUG_ON(clk_prepare_enable(clk));
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/*
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* Tick rate is 2.4MHz for Nomadik and 2.4Mhz, 100MHz or 133 MHz
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* for ux500.
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* Use a divide-by-16 counter if the tick rate is more than 32MHz.
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* At 32 MHz, the timer (with 32 bit counter) can be programmed
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* to wake-up at a max 127s a head in time. Dividing a 2.4 MHz timer
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* with 16 gives too low timer resolution.
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*/
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rate = clk_get_rate(clk);
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if (rate > 32000000) {
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rate /= 16;
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clk_prescale = MTU_CRn_PRESCALE_16;
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} else {
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clk_prescale = MTU_CRn_PRESCALE_1;
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}
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/* Cycles for periodic mode */
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nmdk_cycle = DIV_ROUND_CLOSEST(rate, HZ);
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/* Timer 0 is the free running clocksource */
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nmdk_clksrc_reset();
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ret = clocksource_mmio_init(mtu_base + MTU_VAL(0), "mtu_0",
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rate, 200, 32, clocksource_mmio_readl_down);
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if (ret) {
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pr_err("timer: failed to initialize clock source %s\n", "mtu_0");
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return ret;
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}
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sched_clock_register(nomadik_read_sched_clock, 32, rate);
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/* Timer 1 is used for events, register irq and clockevents */
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setup_irq(irq, &nmdk_timer_irq);
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nmdk_clkevt.cpumask = cpumask_of(0);
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nmdk_clkevt.irq = irq;
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clockevents_config_and_register(&nmdk_clkevt, rate, 2, 0xffffffffU);
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mtu_delay_timer.read_current_timer = &nmdk_timer_read_current_timer;
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mtu_delay_timer.freq = rate;
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register_current_timer_delay(&mtu_delay_timer);
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return 0;
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}
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static int __init nmdk_timer_of_init(struct device_node *node)
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{
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struct clk *pclk;
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struct clk *clk;
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void __iomem *base;
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int irq;
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base = of_iomap(node, 0);
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if (!base) {
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pr_err("Can't remap registers\n");
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return -ENXIO;
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}
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pclk = of_clk_get_by_name(node, "apb_pclk");
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if (IS_ERR(pclk)) {
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pr_err("could not get apb_pclk\n");
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return PTR_ERR(pclk);
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}
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clk = of_clk_get_by_name(node, "timclk");
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if (IS_ERR(clk)) {
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pr_err("could not get timclk\n");
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return PTR_ERR(clk);
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}
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irq = irq_of_parse_and_map(node, 0);
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if (irq <= 0) {
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pr_err("Can't parse IRQ\n");
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return -EINVAL;
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}
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return nmdk_timer_init(base, irq, pclk, clk);
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}
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TIMER_OF_DECLARE(nomadik_mtu, "st,nomadik-mtu",
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nmdk_timer_of_init);
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