Re: [PATCH 1/4] phy: qcom: qmp-combo: delay Type-C mux switch while DP PHY is initializing

From: Saurabh Anand <saurabh.anand@oss.qualcomm.com>
To: Manivannan Sadhasivam <mani@kernel.org>
Cc: Vinod Koul <vkoul@kernel.org>,
	Neil Armstrong <neil.armstrong@linaro.org>,
	Rob Clark <robin.clark@oss.qualcomm.com>,
	Dmitry Baryshkov <lumag@kernel.org>,
	Abhinav Kumar <abhinav.kumar@linux.dev>,
	Jessica Zhang <jesszhan0024@gmail.com>,
	Sean Paul <sean@poorly.run>,
	Marijn Suijten <marijn.suijten@somainline.org>,
	David Airlie <airlied@gmail.com>, Simona Vetter <simona@ffwll.ch>,
	linux-arm-msm@vger.kernel.org, linux-phy@lists.infradead.org,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
	freedreno@lists.freedesktop.org,
	Ritesh Kumar <quic_riteshk@quicinc.com>,
	Vishnuvardhan Prodduturi <quic_vproddut@quicinc.com>,
	Mani Chandana Kuntumalla <quic_mkuntuma@quicinc.com>,
	Mahadevan P <mahadevan.p@oss.qualcomm.com>
Subject: Re: [PATCH 1/4] phy: qcom: qmp-combo: delay Type-C mux switch while DP PHY is initializing
Date: Mon, 7 Sep 2026 15:17:15 +0530	[thread overview]
Message-ID: <902c7a41-363a-4ee7-b780-4d8cf2155d39@oss.qualcomm.com> (raw)
In-Reply-To: <37cs3ejjaldogjlh3oyhzxgedl2w2s6qk7sercwem5j23vdtb4@2dzhapohcgda>

On 02-09-2026 13:18, Manivannan Sadhasivam wrote:
> On Mon, Aug 24, 2026 at 04:58:04PM +0530, Saurabh Anand wrote:
>> The Type-C mux switch guard only checked dp_powered_on, which is set in
>> qmp_combo_dp_power_on(). However there is a race window between
>> qmp_combo_dp_init() and qmp_combo_dp_power_on() during which dp_init_count
>> is non-zero but dp_powered_on is still false. A Type-C orientation change
>> arriving in this window would proceed with the mux switch while the DP PHY
>> is mid-initialization, corrupting the PHY state.
>>
>> Extend the guard to also block the mux switch when dp_init_count is
>> non-zero, covering the full period from dp_init through dp_power_on.
>>
>> Signed-off-by: Saurabh Anand <saurabh.anand@oss.qualcomm.com>
> If this patch fixes a race condition, it should have a Fixes tag.

Sure, will add in next version.

Fixes: 896277138c13 ("phy: qcom: qmp-combo: register a typec mux to 
change the QMPPHY_MODE")

>
> - Mani

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