linux-kernel - Re: [PATCH] firmware: qcom: scm: Allow devicetree-less probe

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Message-ID: <fqdmcct5b5sxv3rpxiksmzpjbpcwmyuwpb5epjnhgpzxh344pp@pxggownwv44n>
Date: Sat, 21 Sep 2024 10:21:36 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Elliot Berman <quic_eberman@...cinc.com>
Cc: Bjorn Andersson <andersson@...nel.org>, 
	Konrad Dybcio <konradybcio@...nel.org>, Bartosz Golaszewski <bartosz.golaszewski@...aro.org>, 
	Andrew Halaney <ahalaney@...hat.com>, Rudraksha Gupta <guptarud@...il.com>, 
	"Linux regression tracking (Thorsten Leemhuis)" <regressions@...mhuis.info>, linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Bartosz Golaszewski <brgl@...ev.pl>
Subject: Re: [PATCH] firmware: qcom: scm: Allow devicetree-less probe

On Fri, Sep 20, 2024 at 11:01:40AM GMT, Elliot Berman wrote:
> Some devicetrees representing Qualcomm Technologies, Inc. SoCs are
> missing the SCM node. Users of the SCM device assume the device is
> present and the driver also assumes it has probed. This can lead to
> unanticipated crashes when there isn't an SCM device. All Qualcomm
> Technologies, Inc. SoCs use SCM to communicate with firmware, so create
> the platform device if it's not present in the devicetree.

Which devicetrees? I assume that this mostly concerns arm32 machines,
but I don't see if you have tested this on any of them. Also on some of
those machines SCM require additional clocks, I don't see that being
handled in the patch.

If we are to manually instantiate SCM node, I'd prefer for it to be
explicit, e.g. MSM8x60, create SCM device, using this-and-that clock.

> Tested that SCM node still probes on:
>  - sm8650-qrd with the SCM DT node still present
>  - sm845-mtp with the SCM DT node still present
>  - sm845-mtp with the node removed
> 
> Fixes: 449d0d84bcd8 ("firmware: qcom: scm: smc: switch to using the SCM allocator")
> Reported-by: Rudraksha Gupta <guptarud@...il.com>
> Closes: https://lore.kernel.org/lkml/692cfe9a-8c05-4ce4-813e-82b3f310019a@gmail.com/
> Link: https://lore.kernel.org/all/CAA8EJpqSKbKJ=y0LAigGdj7_uk+5mezDgnzV5XEzwbxRJgpN1w@mail.gmail.com/
> Suggested-by: Bartosz Golaszewski <brgl@...ev.pl>
> Signed-off-by: Elliot Berman <quic_eberman@...cinc.com>
> ---
>  drivers/firmware/qcom/qcom_scm.c | 75 +++++++++++++++++++++++++++++++++++-----
>  1 file changed, 66 insertions(+), 9 deletions(-)

-- 
With best wishes
Dmitry