linux-kernel - Re: [PATCH v2 2/2] phy: qualcomm: phy-qcom-eusb2-repeater: Don't zero-out registers

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Message-ID: <hgtbmst73ijkfptznqh5r6usdnn2tdx4fxow53g5pyl3yagbh3@4thxrkp5zcnv>
Date: Tue, 17 Jun 2025 15:56:32 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Luca Weiss <luca.weiss@...rphone.com>
Cc: 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>, Abel Vesa <abel.vesa@...aro.org>,
        Konrad Dybcio <konradybcio@...nel.org>, linux-arm-msm@...r.kernel.org,
        linux-phy@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        Neil Armstrong <neil.armstrong@...aro.org>
Subject: Re: [PATCH v2 2/2] phy: qualcomm: phy-qcom-eusb2-repeater: Don't
 zero-out registers

On Tue, Jun 17, 2025 at 10:26:36AM +0200, Luca Weiss wrote:
> Zeroing out registers does not happen in the downstream kernel, and will
> "tune" the repeater in surely unexpected ways since most registers don't
> have a reset value of 0x0.
> 
> Stop doing that and instead just set the registers that are in the init
> sequence (though long term I don't think there's actually PMIC-specific
> init sequences, there's board specific tuning, but that's a story for
> another day).
> 
> Fixes: 99a517a582fc ("phy: qualcomm: phy-qcom-eusb2-repeater: Zero out untouched tuning regs")
> Reviewed-by: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
> Reviewed-by: Neil Armstrong <neil.armstrong@...aro.org>
> Signed-off-by: Luca Weiss <luca.weiss@...rphone.com>
> ---
>  drivers/phy/qualcomm/phy-qcom-eusb2-repeater.c | 83 ++++++++++----------------
>  1 file changed, 30 insertions(+), 53 deletions(-)
> 

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>


-- 
With best wishes
Dmitry