linux-kernel - Re: [RESEND,PATCH 1/2] firmware: qcom: scm: Add SDI disable support

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Message-ID: <ZNliXwJCO14AGceg@localhost>
Date:   Sun, 13 Aug 2023 16:08:15 -0700
From:   Brian Norris <computersforpeace@...il.com>
To:     Robert Marko <robimarko@...il.com>
Cc:     Mukesh Ojha <quic_mojha@...cinc.com>, agross@...nel.org,
        andersson@...nel.org, konrad.dybcio@...aro.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        srichara@...cinc.com
Subject: Re: [RESEND,PATCH 1/2] firmware: qcom: scm: Add SDI disable support

On Fri, May 19, 2023 at 01:16:56PM +0200, Robert Marko wrote:
> On Thu, 18 May 2023 at 16:25, Mukesh Ojha <quic_mojha@...cinc.com> wrote:
> > On 5/18/2023 7:32 PM, Robert Marko wrote:
> > > Some SoC-s like IPQ5018 require SDI(Secure Debug Image) to be disabled
> > > before trying to reboot, otherwise board will just hang after reboot has
> > > been issued via PSCI.
> > >
> > > So, provide a call to SCM that allows disabling it.
> > >
> > > Signed-off-by: Robert Marko <robimarko@...il.com>
> >
> > This scm call support indeed needed for reboot cases, but i am not sure
> > about target specific check in the later patch.
> 
> I am not really sure where to put it, maybe as part of qcom_scm_shutdown?

I would suggest not waiting until shutdown. In fact, I suggest the
opposite -- that this needs to be done as early as possible. Any delay
leaves room for hanging the system -- because a watchdog reset, for
instance, might not be able to trigger an shutdown handler.

And I also imagine that's not the complain Mukesh had; I expect his
reservation was about using the SoC compatible property. But I'd prefer
having that conversation on patch 2.

> Yesterday I found out that in OpenWrt we also have a Google IPQ4019 board that
> has been needing SDI to be disabled as well.

That's me [1] :)

Feel free to CC me on such occasions. I would have loved to have
engaged with this earlier. Anyway, I replied directly to patch 2, since
I think that's a more appropriate place for the discussion.

Brian

[1] Subject: [RFC PATCH] firmware: qcom_scm: disable SDI at boot
    https://lore.kernel.org/all/20200721080054.2803881-1-computersforpeace@gmail.com/