On 11/06/2015 05:02 PM, Guenter Roeck wrote:
On Fri, Nov 06, 2015 at 11:53:42AM -0800, Tim Harvey wrote:
On Thu, Nov 5, 2015 at 2:23 PM, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
On Thu, Nov 05, 2015 at 04:19:21PM -0500, Akshay Bhat wrote:
From: Tim Harvey <tharvey@xxxxxxxxxxxxx>
The IMX6 watchdog supports assertion of a signal (WDOG_B) which
can be pinmux'd to an external pin. This is typically used for boards that
have PMIC's in control of the IMX6 power rails. In fact, failure to use
such an external reset on boards with external PMIC's can result in various
hangs due to the IMX6 not being fully reset [1] as well as the board failing
to reset because its PMIC has not been reset to provide adequate voltage for
the CPU when coming out of reset at 800Mhz.
This uses a new device-tree property 'ext-reset-output' to indicate the
board has such a reset and to cause the watchdog to be configured to assert
WDOG_B instead of an internal reset both on a watchdog timeout and in
system_restart.
[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-March/333689.html
Cc: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
Signed-off-by: Tim Harvey <tharvey@xxxxxxxxxxxxx>
---
.../devicetree/bindings/watchdog/fsl-imx-wdt.txt | 2 ++
drivers/watchdog/imx2_wdt.c | 20 ++++++++++++++++++--
2 files changed, 20 insertions(+), 2 deletions(-)
diff --git a/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt b/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt
index 8dab6fd..9b89b3a 100644
--- a/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt
+++ b/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.txt
@@ -9,6 +9,8 @@ Optional property:
properties ?
- big-endian: If present the watchdog device's registers are implemented
in big endian mode, otherwise in native mode(same with CPU), for more
detail please see: Documentation/devicetree/bindings/regmap/regmap.txt.
+- ext-reset-output: If present the watchdog device is configured to assert its
Should that have a vendor prefix ? Also, not sure if "-output"
has any real value in the property name. "fsl,external-reset", maybe ?
Hi Guenter,
I don't see why a vendor prefix is necessary - its a feature of the
IMX6 watchdog supported by this driver to be able to trigger an
internal chip-level reset and/or an external signal that can be hooked
to additional hardware.
Sounded like vendor specific to me, but then I am not a devicetree maintainer,
so I am not an authority on the subject.
Devicetree maintainers,
Any thoughts?
Tim,
After looking at all the other watchdog drivers, it does not appear that
there is any other processor which uses a similar feature. Since imx is
the only processor that appears to support this feature, it might make
sense in making this vendor specific. If in the future it is found more
processors support a similar functionality, it can be revisited and
moved out from being vendor specific?
I started with ext-reset, but it was suggested
(http://lists.infradead.org/pipermail/linux-arm-kernel/2015-May/347437.html)
to also make it clear that this is an 'output' and not a reset input.
No problem, as long as you get an Ack from a devicetree maintainer.
Guenter
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