> -----Original Message-----
> From: Alexandre Belloni [mailto:alexandre.bell...@free-electrons.com]
> Sent: 2017年3月3日 1:31
> To: Guenter Roeck <li...@roeck-us.net>
> Cc: Wim Van Sebroeck <w...@iguana.be>; Nicolas Ferre - M43238
> <nicolas.fe...@microchip.com>; Wenyou Yang - A41535
> <wenyou.y...@microchip.com>; linux-watch...@vger.kernel.org; linux-arm-
> ker...@lists.infradead.org; linux-kernel@vger.kernel.org; Alexandre Belloni
> <alexandre.bell...@free-electrons.com>
> Subject: [PATCH 2/4] 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.
Indeed.
Acked-by: Wenyou.Yang <wenyou.y...@microchip.com>
Thanks
>
> Signed-off-by: Alexandre Belloni <alexandre.bell...@free-electrons.com>
> ---
> drivers/watchdog/sama5d4_wdt.c | 33 +++++++++++++++++++++++++++++----
> 1 file 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);
>
> --
> 2.11.0
Best Regards,
Wenyou Yang
