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authorAlexandre Belloni <alexandre.belloni@free-electrons.com>2017-03-02 18:31:12 +0100
committerWim Van Sebroeck <wim@iguana.be>2017-05-18 18:51:24 +0200
commitddd6d240b26dcb8b8dc98bd493eba944dd97ebc8 (patch)
tree3841ccf38b20b4e0b3adbb3aa12c801cff69450e
parent015b528644a84b0018d3286ecd6ea5f82dce0180 (diff)
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>
-rw-r--r--drivers/watchdog/sama5d4_wdt.c33
1 files changed, 29 insertions, 4 deletions
diff --git a/drivers/watchdog/sama5d4_wdt.c b/drivers/watchdog/sama5d4_wdt.c
index 5cee20caca78..362fd229786d 100644
--- a/drivers/watchdog/sama5d4_wdt.c
+++ b/drivers/watchdog/sama5d4_wdt.c
@@ -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);