Re: [PATCH 09/15] rpmsg: smd: Drop unnecessary condition for channel creation

Stephan Gerhold
2022-01-16T16:31:09Z

On Sun, Jan 16, 2022 at 05:08:29PM +0100, Luca Weiss wrote:
> On Mittwoch, 12. Jänner 2022 22:39:53 CET Stephan Gerhold wrote:
> > On Wed, Jan 12, 2022 at 08:40:58PM +0100, Luca Weiss wrote:
> > > From: Vladimir Lypak <vladimir.lypak@gmail.com>
> > >
> > > RPM Firmware on variety of newer SoCs such as MSM8917 (also likely
> > > MSM8937, MSM8940, MSM8952), MSM8953 and on some MSM8916 devices) doesn't
> > > initiate opening of the SMD channel if it was previously opened by
> > > bootloader. This doesn't allow probing of smd-rpm driver on such devices
> > > because there is a check that requires RPM this behaviour.
> > >
> > > Signed-off-by: Vladimir Lypak <vladimir.lypak@gmail.com>
> > > Signed-off-by: Luca Weiss <luca@z3ntu.xyz>
> > > Reviewed-by: Konrad Dybcio <konrad.dybcio@somainline.org>
> >
> > This is effectively a "Revert "Revert "rpmsg: smd: Create device for all
> > channels""":
> >
> > https://lore.kernel.org/linux-arm-msm/20171212235857.10432-3-bjorn.andersson
> > @linaro.org/
> > https://lore.kernel.org/linux-arm-msm/20180315181244.8859-1-bjorn.andersson
> > @linaro.org/
> >
> > Won't this cause the same regression reported by Srinivas again?
> >
>
> Do you have any suggestion on another way to solve this? Without this commit
> the regulators just won't probe at all, I haven't looked very deep into it
> though given this patch solves it.
>
> I guess worst case it'll become a devicetree property to enable this quirk?
>

My spontaneous suggestion would be to skip the check only for the
"rpm_requests" channel, e.g. something like

if (remote_state != SMD_CHANNEL_OPENING &&
remote_state != SMD_CHANNEL_OPENED &&
strcmp(channel->name, "rpm_requests")
continue;

This will avoid changing the behavior for anything but the RPM channel.
I don't think anything else is affected by the same problem (since the
bootloader or earlier firmware should not make use of any other channel).
Also, we definitely *always* want to open the channel to the RPM because
otherwise almost everything breaks.

Many solutions are possible though so at the end it is mostly up to
Bjorn to decide I think. :)

Thanks,
Stephan