Re: [PATCH] phy: qualcomm: qmp-combo: update DP PHY PLL programming on Glymur

From: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
To: Mahadevan P <mahadevan.p@oss.qualcomm.com>,
	Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Cc: Vinod Koul <vkoul@kernel.org>,
	Neil Armstrong <neil.armstrong@linaro.org>,
	Wesley Cheng <wesley.cheng@oss.qualcomm.com>,
	Abel Vesa <abelvesa@kernel.org>,
	Bjorn Andersson <andersson@kernel.org>,
	Konrad Dybcio <konradybcio@kernel.org>,
	Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>,
	linux-arm-msm@vger.kernel.org, linux-phy@lists.infradead.org,
	linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
	Ritesh Kumar <ritesh.kumar@oss.qualcomm.com>
Subject: Re: [PATCH] phy: qualcomm: qmp-combo: update DP PHY PLL programming on Glymur
Date: Wed, 22 Apr 2026 11:54:30 +0200	[thread overview]
Message-ID: <b21b1f73-881a-40bd-aef6-5c34aed0e266@oss.qualcomm.com> (raw)
In-Reply-To: <a967d7ec-66f7-4eaa-91e3-0a96e5a8ec7f@oss.qualcomm.com>

On 4/20/26 4:18 PM, Mahadevan P wrote:
> 
> 
> On 4/19/2026 6:48 PM, Dmitry Baryshkov wrote:
>> On Sun, 19 Apr 2026 at 13:16, Mahadevan P <mahadevan.p@oss.qualcomm.com> wrote:
>>>
>>> The existing DP PHY PLL and AUX configuration for the Glymur platform
>>> does not fully follow the Hardware Programming Guide requirements for
>>> DP over Type-C, which results in DP link bring-up failures.
>>>
>>> Update the DP PHY programming sequence and PLL-related register
>>> settings to align with the latest HPG recommendations. With this
>>> change, DP link training completes successfully on Glymur-based
>>> platforms.
>>>
>>> Fixes: d10736db98d2 ("phy: qualcomm: qmp-combo: Add DP offsets and settings for Glymur platforms")
>>> Signed-off-by: Ritesh Kumar <ritesh.kumar@oss.qualcomm.com>
>>> Signed-off-by: Mahadevan P <mahadevan.p@oss.qualcomm.com>
>>> ---

[...]

>>> +       writel(val, qmp->dp_dp_phy + QSERDES_DP_PHY_PD_CTL);
>>> +
>>> +       writel(0x5c, qmp->dp_dp_phy + QSERDES_DP_PHY_MODE);
>>
>> Are you saying that we don't need to write 0x4c here in case of the
>> reverse mode? Was that changed and why?
> Yes for glymur it is changed
> DP2_PHY_DP_PHY_PD_CTL
> Normal Orientation: 0x7D for 4lane; 0x75 for 1Lane or 2Lanne
> Flip Orientation: 0x7D for 4Lane; 0x6D for 1Lane or 2Lane

Dmitry asked about the other register - DP_PHY_MODE.

I checked the reg description, and at least for Glymur, BIT(5)
(the difference between 0x4c and 0x5c) says "take bit 4 into
consideration, otherwise let the HW decide". I wonder if we need
to set it at all, for any target.

Konrad

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