Re: [PATCH RESEND] watchdog: apple: Increase reset delay to 150ms
From: "Arnd Bergmann" <arnd@arndb.de>
Date: 2024-09-30 09:38:34
Also in:
asahi, linux-watchdog, lkml
On Mon, Sep 30, 2024, at 06:06, Nick Chan wrote:
quoted hunk ↗ jump to hunk
The Apple A8X SoC seems to be slowest at resetting, taking up to around 125ms to reset. Wait 150ms to be safe here. Reviewed-by: Sven Peter <redacted> Reviewed-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Nick Chan <redacted> --- drivers/watchdog/apple_wdt.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)diff --git a/drivers/watchdog/apple_wdt.c b/drivers/watchdog/apple_wdt.c index d4f739932f0b..353ecf0b04dc 100644 --- a/drivers/watchdog/apple_wdt.c +++ b/drivers/watchdog/apple_wdt.c@@ -127,11 +127,11 @@ static int apple_wdt_restart(structwatchdog_device *wdd, unsigned long mode, /* * Flush writes and then wait for the SoC to reset. Even though the * reset is queued almost immediately experiments have shown that it - * can take up to ~20-25ms until the SoC is actually reset. Just wait - * 50ms here to be safe. + * can take up to ~120-125ms until the SoC is actually reset. Just + * wait 150ms here to be safe. */ (void)readl_relaxed(wdt->regs + APPLE_WDT_WD1_CUR_TIME); - mdelay(50); + mdelay(150);
I think you also need to insert a barrier before the mdelay(),
or turn the readl_relaxed() into a readl(), it will otherwise
be bypassed by the delay.
The comment is a bit confusing here as it suggests that the
MMIO read is meant to serialize between the restart and the
mdelay(), but the _relaxed() annotation on the readl()
explicitly skips that serialization, so one of the two is
wrong here.
Arnd