linux-kernel - Re: [PATCH] pmdomain: qcom: rpmhpd: Fix enabled

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Date: Tue, 27 Feb 2024 04:11:59 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: quic_bjorande@...cinc.com
Cc: Bjorn Andersson <andersson@...nel.org>, Konrad Dybcio <konrad.dybcio@...aro.org>, 
	Ulf Hansson <ulf.hansson@...aro.org>, Stephen Boyd <swboyd@...omium.org>, 
	Johan Hovold <johan+linaro@...nel.org>, linux-arm-msm@...r.kernel.org, 
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Johan Hovold <johan@...nel.org>, stable@...r.kernel.org
Subject: Re: [PATCH] pmdomain: qcom: rpmhpd: Fix enabled_corner aggregation

On Tue, 27 Feb 2024 at 03:45, Bjorn Andersson via B4 Relay
<devnull+quic_bjorande.quicinc.com@...nel.org> wrote:
>
> From: Bjorn Andersson <quic_bjorande@...cinc.com>
>
> Commit 'e3e56c050ab6 ("soc: qcom: rpmhpd: Make power_on actually enable
> the domain")' aimed to make sure that a power-domain that is being
> enabled without any particular performance-state requested will at least
> turn the rail on, to avoid filling DeviceTree with otherwise unnecessary
> required-opps properties.
>
> But in the event that aggregation happens on a disabled power-domain, with
> an enabled peer without performance-state, both the local and peer
> corner are 0. The peer's enabled_corner is not considered, with the
> result that the underlying (shared) resource is disabled.
>
> One case where this can be observed is when the display stack keeps mmcx
> enabled (but without a particular performance-state vote) in order to
> access registers and sync_state happens in the rpmhpd driver. As mmcx_ao
> is flushed the state of the peer (mmcx) is not considered and mmcx_ao
> ends up turning off "mmcx.lvl" underneath mmcx. This has been observed
> several times, but has been painted over in DeviceTree by adding an
> explicit vote for the lowest non-disabled performance-state.
>
> Fixes: e3e56c050ab6 ("soc: qcom: rpmhpd: Make power_on actually enable the domain")
> Reported-by: Johan Hovold <johan@...nel.org>
> Closes: https://lore.kernel.org/linux-arm-msm/ZdMwZa98L23mu3u6@hovoldconsulting.com/
> Cc:  <stable@...r.kernel.org>
> Signed-off-by: Bjorn Andersson <quic_bjorande@...cinc.com>
> ---
> This issue is the root cause of a display regression on SC8280XP boards,
> resulting in the system often resetting during boot. It was exposed by
> the refactoring of the DisplayPort driver in v6.8-rc1.
> ---
>  drivers/pmdomain/qcom/rpmhpd.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Tested-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>

Probably once this lands we can drop explicit required-opps properties.

-- 
With best wishes
Dmitry