linux-kernel - Re: [PATCH v4 5/6] phy: qcom: qmp-combo: register a typec mux to change the QMPPHY

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Message-ID: <4f6a7dc5-b0f8-491b-aa12-78be5f47ef2b@oss.qualcomm.com>
Date: Mon, 11 Aug 2025 13:12:59 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Konrad Dybcio <konradybcio@...nel.org>, Vinod Koul <vkoul@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
 <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Neil Armstrong <neil.armstrong@...aro.org>
Subject: Re: [PATCH v4 5/6] phy: qcom: qmp-combo: register a typec mux to
 change the QMPPHY_MODE

On 8/11/25 12:55 PM, Dmitry Baryshkov wrote:
> On Mon, Aug 11, 2025 at 12:37:00PM +0200, Konrad Dybcio wrote:
>> On 8/9/25 10:13 AM, Dmitry Baryshkov wrote:
>>> On Thu, Aug 07, 2025 at 06:33:23PM +0200, Konrad Dybcio wrote:
>>>> From: Neil Armstrong <neil.armstrong@...aro.org>
>>>>
>>>> Register a typec mux in order to change the PHY mode on the Type-C
>>>> mux events depending on the mode and the svid when in Altmode setup.
>>>>
>>>> The DisplayPort phy should be left enabled if is still powered on
>>>> by the DRM DisplayPort controller, so bail out until the DisplayPort
>>>> PHY is not powered off.
>>>>
>>>> The Type-C Mode/SVID only changes on plug/unplug, and USB SAFE states
>>>> will be set in between of USB-Only, Combo and DisplayPort Only so
>>>> this will leave enough time to the DRM DisplayPort controller to
>>>> turn of the DisplayPort PHY.
>>>>
>>>> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
>>>> [konrad: renaming, rewording, bug fixes]
>>>> Signed-off-by: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
>>>> ---
>>>>  drivers/phy/qualcomm/phy-qcom-qmp-combo.c | 118 ++++++++++++++++++++++++++++--
>>>>  1 file changed, 113 insertions(+), 5 deletions(-)
>>>>
>>>> +
>>>> +	if (qmp->qmpphy_mode != QMPPHY_MODE_USB3_ONLY && qmp->dp_powered_on) {
>>>> +		dev_dbg(qmp->dev, "typec_mux_set: DP PHY is still in use, delaying switch\n");
>>>> +		return 0;
>>>> +	}
>>>
>>> I can't say that I'm fully happy about it, nevertheless:
>>>
>>> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
>>
>> IIUC we'll be able to get rid of it after the dp rework?
> 
> Which one? The HPD? not really. My unhappiness is about the sync between
> USB and DP. I'm unsure whether we need higher level of sync for
> USB-or-DP PHYs.

Unfortunately it'll only get worse with usb4, where the DP PLL may
need to be online (or not) for when we're tunneling DP data :(

Konrad