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Date: Tue, 27 Feb 2024 10:15:10 +0100
From: Johan Hovold <johan@kernel.org>
To: quic_bjorande@quicinc.com
Cc: Bjorn Andersson <andersson@kernel.org>,
	Konrad Dybcio <konrad.dybcio@linaro.org>,
	Ulf Hansson <ulf.hansson@linaro.org>,
	Stephen Boyd <swboyd@chromium.org>,
	Johan Hovold <johan+linaro@kernel.org>,
	Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
	linux-arm-msm@vger.kernel.org, linux-pm@vger.kernel.org,
	linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH] pmdomain: qcom: rpmhpd: Fix enabled_corner aggregation
Message-ID: <Zd2oHl0cVQr3mhmd@hovoldconsulting.com>
References: <20240226-rpmhpd-enable-corner-fix-v1-1-68c004cec48c@quicinc.com>
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In-Reply-To: <20240226-rpmhpd-enable-corner-fix-v1-1-68c004cec48c@quicinc.com>

On Mon, Feb 26, 2024 at 05:49:57PM -0800, Bjorn Andersson via B4 Relay wrote:
> From: Bjorn Andersson <quic_bjorande@quicinc.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@kernel.org>
> Closes: https://lore.kernel.org/linux-arm-msm/ZdMwZa98L23mu3u6@hovoldconsulting.com/
> Cc:  <stable@vger.kernel.org>
> Signed-off-by: Bjorn Andersson <quic_bjorande@quicinc.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.

This fixes the hard resets I've been seeing since rc1 when initialising
the display subsystem of the Lenovo ThinkPad X13s at boot. With some
instrumentation added I can see the resets coinciding with the call to
rpmhpd_aggregate_corner() for 'mx_ao':

Tested-by: Johan Hovold <johan+linaro@kernel.org>