> -----Original Message----- > From: Alexandre Belloni [mailto:alexandre.belloni@xxxxxxxxxxxxxxxxxx] > Sent: 2017年3月3日 1:31 > To: Guenter Roeck <linux@xxxxxxxxxxxx> > Cc: Wim Van Sebroeck <wim@xxxxxxxxx>; Nicolas Ferre - M43238 > <Nicolas.Ferre@xxxxxxxxxxxxx>; Wenyou Yang - A41535 > <Wenyou.Yang@xxxxxxxxxxxxx>; linux-watchdog@xxxxxxxxxxxxxxx; linux-arm- > kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Alexandre Belloni > <alexandre.belloni@xxxxxxxxxxxxxxxxxx> > 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.yang@xxxxxxxxxxxxx> Thanks > > Signed-off-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx> > --- > 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 ��.n��������+%������w��{.n�����{���rh���ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f
