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

On 07/15/2012 09:07 PM, Lu.Jiang wrote:

=E4=BA=8E 2012=E5=B9=B407=E6=9C=8813=E6=97=A5 19:50, Kumar Gala =E5=86=99=

=E9=81=93:

quoted

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'

=20
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 reboo=

t

immediately.
=20
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.

This is (supposed to be) true on FSL e500 as well.

While on FSL's platform, we did not met such issue.

You tested this and were able to clear WRC on an e500-based chip?  Which
one?

-Scott