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Commit ddd6d240 authored by Alexandre Belloni's avatar Alexandre Belloni Committed by Wim Van Sebroeck
Browse files

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: default avatarAlexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: default avatarWenyou.Yang <wenyou.yang@microchip.com>
Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
Signed-off-by: default avatarWim Van Sebroeck <wim@iguana.be>
parent 015b5286

drivers/watchdog/sama5d4_wdt.c

+29 −4
Original line number Diff line number Diff line
@@ -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);