eb39a7c035
The interrupt handler mfgpt_tick() is not robust versus spurious interrupts
which happen before the clock event device is registered and fully
initialized.
The reason is that the safe guard against spurious interrupts solely checks
for the clockevents shutdown state, but lacks a check for detached
state. If the interrupt hits while the device is in detached state it
passes the safe guard and dereferences the event handler call back which is
NULL.
Add the missing state check.
Fixes: 8f9327cbb6 ("clockevents/drivers/cs5535: Migrate to new 'set-state' interface")
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David Kozub <zub@linux.fjfi.cvut.cz>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20171020093103.3317F6004D@linux.fjfi.cvut.cz
196 lines
5.8 KiB
C
196 lines
5.8 KiB
C
/*
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* Clock event driver for the CS5535/CS5536
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*
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* Copyright (C) 2006, Advanced Micro Devices, Inc.
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* Copyright (C) 2007 Andres Salomon <dilinger@debian.org>
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* Copyright (C) 2009 Andres Salomon <dilinger@collabora.co.uk>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of version 2 of the GNU General Public License
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* as published by the Free Software Foundation.
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*
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* The MFGPTs are documented in AMD Geode CS5536 Companion Device Data Book.
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*/
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#include <linux/kernel.h>
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#include <linux/irq.h>
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#include <linux/interrupt.h>
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#include <linux/module.h>
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#include <linux/cs5535.h>
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#include <linux/clockchips.h>
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#define DRV_NAME "cs5535-clockevt"
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static int timer_irq;
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module_param_hw_named(irq, timer_irq, int, irq, 0644);
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MODULE_PARM_DESC(irq, "Which IRQ to use for the clock source MFGPT ticks.");
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/*
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* We are using the 32.768kHz input clock - it's the only one that has the
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* ranges we find desirable. The following table lists the suitable
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* divisors and the associated Hz, minimum interval and the maximum interval:
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*
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* Divisor Hz Min Delta (s) Max Delta (s)
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* 1 32768 .00048828125 2.000
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* 2 16384 .0009765625 4.000
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* 4 8192 .001953125 8.000
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* 8 4096 .00390625 16.000
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* 16 2048 .0078125 32.000
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* 32 1024 .015625 64.000
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* 64 512 .03125 128.000
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* 128 256 .0625 256.000
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* 256 128 .125 512.000
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*/
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static struct cs5535_mfgpt_timer *cs5535_event_clock;
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/* Selected from the table above */
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#define MFGPT_DIVISOR 16
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#define MFGPT_SCALE 4 /* divisor = 2^(scale) */
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#define MFGPT_HZ (32768 / MFGPT_DIVISOR)
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#define MFGPT_PERIODIC (MFGPT_HZ / HZ)
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/*
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* The MFGPT timers on the CS5536 provide us with suitable timers to use
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* as clock event sources - not as good as a HPET or APIC, but certainly
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* better than the PIT. This isn't a general purpose MFGPT driver, but
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* a simplified one designed specifically to act as a clock event source.
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* For full details about the MFGPT, please consult the CS5536 data sheet.
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*/
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static void disable_timer(struct cs5535_mfgpt_timer *timer)
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{
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/* avoid races by clearing CMP1 and CMP2 unconditionally */
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cs5535_mfgpt_write(timer, MFGPT_REG_SETUP,
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(uint16_t) ~MFGPT_SETUP_CNTEN | MFGPT_SETUP_CMP1 |
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MFGPT_SETUP_CMP2);
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}
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static void start_timer(struct cs5535_mfgpt_timer *timer, uint16_t delta)
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{
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cs5535_mfgpt_write(timer, MFGPT_REG_CMP2, delta);
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cs5535_mfgpt_write(timer, MFGPT_REG_COUNTER, 0);
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cs5535_mfgpt_write(timer, MFGPT_REG_SETUP,
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MFGPT_SETUP_CNTEN | MFGPT_SETUP_CMP2);
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}
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static int mfgpt_shutdown(struct clock_event_device *evt)
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{
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disable_timer(cs5535_event_clock);
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return 0;
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}
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static int mfgpt_set_periodic(struct clock_event_device *evt)
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{
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disable_timer(cs5535_event_clock);
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start_timer(cs5535_event_clock, MFGPT_PERIODIC);
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return 0;
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}
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static int mfgpt_next_event(unsigned long delta, struct clock_event_device *evt)
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{
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start_timer(cs5535_event_clock, delta);
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return 0;
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}
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static struct clock_event_device cs5535_clockevent = {
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.name = DRV_NAME,
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.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
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.set_state_shutdown = mfgpt_shutdown,
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.set_state_periodic = mfgpt_set_periodic,
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.set_state_oneshot = mfgpt_shutdown,
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.tick_resume = mfgpt_shutdown,
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.set_next_event = mfgpt_next_event,
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.rating = 250,
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};
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static irqreturn_t mfgpt_tick(int irq, void *dev_id)
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{
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uint16_t val = cs5535_mfgpt_read(cs5535_event_clock, MFGPT_REG_SETUP);
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/* See if the interrupt was for us */
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if (!(val & (MFGPT_SETUP_SETUP | MFGPT_SETUP_CMP2 | MFGPT_SETUP_CMP1)))
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return IRQ_NONE;
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/* Turn off the clock (and clear the event) */
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disable_timer(cs5535_event_clock);
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if (clockevent_state_detached(&cs5535_clockevent) ||
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clockevent_state_shutdown(&cs5535_clockevent))
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return IRQ_HANDLED;
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/* Clear the counter */
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cs5535_mfgpt_write(cs5535_event_clock, MFGPT_REG_COUNTER, 0);
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/* Restart the clock in periodic mode */
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if (clockevent_state_periodic(&cs5535_clockevent))
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cs5535_mfgpt_write(cs5535_event_clock, MFGPT_REG_SETUP,
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MFGPT_SETUP_CNTEN | MFGPT_SETUP_CMP2);
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cs5535_clockevent.event_handler(&cs5535_clockevent);
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return IRQ_HANDLED;
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}
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static struct irqaction mfgptirq = {
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.handler = mfgpt_tick,
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.flags = IRQF_NOBALANCING | IRQF_TIMER | IRQF_SHARED,
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.name = DRV_NAME,
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};
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static int __init cs5535_mfgpt_init(void)
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{
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struct cs5535_mfgpt_timer *timer;
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int ret;
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uint16_t val;
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timer = cs5535_mfgpt_alloc_timer(MFGPT_TIMER_ANY, MFGPT_DOMAIN_WORKING);
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if (!timer) {
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printk(KERN_ERR DRV_NAME ": Could not allocate MFGPT timer\n");
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return -ENODEV;
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}
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cs5535_event_clock = timer;
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/* Set up the IRQ on the MFGPT side */
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if (cs5535_mfgpt_setup_irq(timer, MFGPT_CMP2, &timer_irq)) {
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printk(KERN_ERR DRV_NAME ": Could not set up IRQ %d\n",
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timer_irq);
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goto err_timer;
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}
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/* And register it with the kernel */
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ret = setup_irq(timer_irq, &mfgptirq);
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if (ret) {
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printk(KERN_ERR DRV_NAME ": Unable to set up the interrupt.\n");
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goto err_irq;
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}
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/* Set the clock scale and enable the event mode for CMP2 */
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val = MFGPT_SCALE | (3 << 8);
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cs5535_mfgpt_write(cs5535_event_clock, MFGPT_REG_SETUP, val);
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/* Set up the clock event */
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printk(KERN_INFO DRV_NAME
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": Registering MFGPT timer as a clock event, using IRQ %d\n",
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timer_irq);
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clockevents_config_and_register(&cs5535_clockevent, MFGPT_HZ,
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0xF, 0xFFFE);
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return 0;
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err_irq:
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cs5535_mfgpt_release_irq(cs5535_event_clock, MFGPT_CMP2, &timer_irq);
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err_timer:
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cs5535_mfgpt_free_timer(cs5535_event_clock);
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printk(KERN_ERR DRV_NAME ": Unable to set up the MFGPT clock source\n");
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return -EIO;
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}
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module_init(cs5535_mfgpt_init);
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MODULE_AUTHOR("Andres Salomon <dilinger@queued.net>");
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MODULE_DESCRIPTION("CS5535/CS5536 MFGPT clock event driver");
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MODULE_LICENSE("GPL");
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