Re: [PATCH] ppc44x/watchdog: Select WATCHDOG_NOWAYOUT option

于 2012年07月13日 19:50, Kumar Gala 写道:

On Jul 12, 2012, at 9:44 PM, Jiang Lu wrote:

quoted

On PPC44x core, the WRC(Watchdog-timer Reset Control) field of TCR
of timer can not reset by software after set to a non-zero value.
Which means software can not reset the timeout behaviour of watchdog timer.

This patch selects WATCHDOG_NOWAYOUT option for 44x platforms to
indicate the watchdog timer can not be disabled once fired.

Signed-off-by: Jiang Lu <redacted>
---
drivers/watchdog/Kconfig |    1 +
1 files changed, 1 insertions(+), 0 deletions(-)

I believe this is not 44x specific, but how Book-E watchdog is architected.

quoted

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 3709624..41f3dff 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig

@@ -1084,6 +1084,7 @@ config PIKA_WDT

config BOOKE_WDT
	tristate "PowerPC Book-E Watchdog Timer"
	depends on BOOKE || 4xx
+	select WATCHDOG_NOWAYOUT if 44x

This should probably be 'select WATCHDOG_NOWAYOUT if BOOKE'

On ppc44x's processor, if we disabled 'WATCHDOG_NOWAYOUT ' option. The driver's release routine will try to disable the watchdog , by clearing the WIE & WTDP field in TCR.
Since the ppc44x's watch dog can not reset by software, such operation only set the timeout value(WDTP) to minimum, and cause the system reboot immediately.

I checked ppc 476, 405 & 450's manual, these document said the WRC(Watchdog-timer Reset Control) field of TCR of timer
can not reset by software after set to a non-zero value. I think all ppc44x core should got same limitation.

While on FSL's platform, we did not met such issue. So I think we should select 'WATCHDOG_NOWAYOUT' option for 44x platform.

Regards,
Jiang Lu

quoted

	---help---
	  Watchdog driver for PowerPC Book-E chips, such as the Freescale
	  MPC85xx SOCs and the IBM PowerPC 440.
-- 
1.7.7

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