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watchdog: sama5d4: fix race condition 

WDT_MR and WDT_CR must not updated within three slow clock periods after
the last ping (write to WDT_CR or WDT_MR). Ensure enough time has elapsed
before writing those registers.
wdt_write() waits for 4 periods to ensure at least 3 edges are seen by the
IP.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Wenyou.Yang <wenyou.yang@microchip.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
hifive-unleashed-5.1
Alexandre Belloni 2017-03-02 18:31:12 +01:00 committed by Wim Van Sebroeck
parent 015b528644
commit ddd6d240b2
1 changed files with 29 additions and 4 deletions
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33
drivers/watchdog/sama5d4_wdt.c
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@ -6,6 +6,7 @@
* Licensed under GPLv2.
*/
#include <linux/delay.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/kernel.h>
@ -29,6 +30,7 @@ struct sama5d4_wdt {
struct watchdog_device wdd;
void __iomem *reg_base;
u32 mr;
unsigned long last_ping;
};
static int wdt_timeout = WDT_DEFAULT_TIMEOUT;
@ -49,8 +51,29 @@ MODULE_PARM_DESC(nowayout,
#define wdt_read(wdt, field) \
readl_relaxed((wdt)->reg_base + (field))
#define wdt_write(wtd, field, val) \
writel_relaxed((val), (wdt)->reg_base + (field))
/* 4 slow clock periods is 4/32768 = 122.07µs*/
#define WDT_DELAY usecs_to_jiffies(123)
static void wdt_write(struct sama5d4_wdt *wdt, u32 field, u32 val)
{
/*
* WDT_CR and WDT_MR must not be modified within three slow clock
* periods following a restart of the watchdog performed by a write
* access in WDT_CR.
*/
while (time_before(jiffies, wdt->last_ping + WDT_DELAY))
usleep_range(30, 125);
writel_relaxed(val, wdt->reg_base + field);
wdt->last_ping = jiffies;
}
static void wdt_write_nosleep(struct sama5d4_wdt *wdt, u32 field, u32 val)
{
if (time_before(jiffies, wdt->last_ping + WDT_DELAY))
udelay(123);
writel_relaxed(val, wdt->reg_base + field);
wdt->last_ping = jiffies;
}
static int sama5d4_wdt_start(struct watchdog_device *wdd)
{
@ -164,11 +187,12 @@ static int sama5d4_wdt_init(struct sama5d4_wdt *wdt)
* Else, we have to disable it properly.
*/
if (wdt_enabled) {
wdt_write(wdt, AT91_WDT_MR, wdt->mr);
wdt_write_nosleep(wdt, AT91_WDT_MR, wdt->mr);
} else {
reg = wdt_read(wdt, AT91_WDT_MR);
if (!(reg & AT91_WDT_WDDIS))
wdt_write(wdt, AT91_WDT_MR, reg | AT91_WDT_WDDIS);
wdt_write_nosleep(wdt, AT91_WDT_MR,
reg | AT91_WDT_WDDIS);
}
return 0;
}
@ -193,6 +217,7 @@ static int sama5d4_wdt_probe(struct platform_device *pdev)
wdd->ops = &sama5d4_wdt_ops;
wdd->min_timeout = MIN_WDT_TIMEOUT;
wdd->max_timeout = MAX_WDT_TIMEOUT;
wdt->last_ping = jiffies;
watchdog_set_drvdata(wdd, wdt);