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SubjectRe: [PATCH v2] platform/chrome: cros_ec_typec: Check for EC device
Hi Prashant,

On Wed, Jan 26, 2022 at 11:08:14PM +0000, Prashant Malani wrote:
> Hi Alyssa,
>
> On Jan 26 23:04, Alyssa Ross wrote:
> > On Wed, Jan 26, 2022 at 07:02:20PM +0000, Prashant Malani wrote:
> > > The Type C ACPI device on older Chromebooks is not generated correctly
> > > (since their EC firmware doesn't support the new commands required). In
> > > such cases, the crafted ACPI device doesn't have an EC parent, and it is
> > > therefore not useful (it shouldn't be generated in the first place since
> > > the EC firmware doesn't support any of the Type C commands).
> > >
> > > To handle devices which use these older firmware revisions, check for
> > > the parent EC device handle, and fail the probe if it's not found.
> > >
> > > Fixes: fdc6b21e2444 ("platform/chrome: Add Type C connector class driver")
> > > Reported-by: Alyssa Ross <hi@alyssa.is>
> > > Reviewed-by: Tzung-Bi Shih <tzungbi@google.com>
> > > Signed-off-by: Prashant Malani <pmalani@chromium.org>
> > > ---
> > > Hi Alyssa, could you kindly test this with your existing setup? Thanks!
> >
> > Hi Prashant, I'm happy to test, but I'm on vacation until the end of the
> > week so probably won't get a chance before Monday.
>
> No worries, whenever you get the chance is fine.
>
> >
> > I'm guessing I should be testing with latest upstream coreboot (now that
> > your fix there has been applied)?
>
> You should use the coreboot with which you discovered the crash, so the
> one which *doesn't* contain the fix.

I applied this patch to Linux 5.17-rc2 and tested with the
coreboot_tiano-eve-mrchromebox-20210806.rom firmware.

The Oops has been replaced with
"cros-ec-typec: GOOG0014:00: couldn't find parent EC device".
My laptop now reboots correctly — the hang on reboot is gone.

The cros_ec_typec driver ends up being loaded, but no devices are bound
to it. This differs from the behaviour with upstream coreboot
(cabf9e33a7), where cros_ec_typec does not end up being loaded.

Assuming all that's the intended behaviour:

Reviewed-by: Alyssa Ross <hi@alyssa.is>
Tested-by: Alyssa Ross <hi@alyssa.is>

BTW: if you need anything else tested on an eve running upstream Linux
and Coreboot in future, I'm happy to be CCed. :)

> Thanks again!
>
> -Prashant
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