linux-kernel - Re: [PATCH] phy: qcom: qmp-combo: Fix VCO div offset on v3

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Message-ID: <CAA8EJprZ8Ehx+M7vy1pH8OT6Of2v8-trecCJZhF5wxBRSGQoXw@mail.gmail.com>
Date: Fri, 5 Apr 2024 05:54:49 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Stephen Boyd <swboyd@...omium.org>
Cc: Vinod Koul <vkoul@...nel.org>, Kishon Vijay Abraham I <kishon@...nel.org>, linux-kernel@...r.kernel.org, 
	patches@...ts.linux.dev, linux-arm-msm@...r.kernel.org, 
	Konrad Dybcio <konrad.dybcio@...aro.org>, Bjorn Andersson <andersson@...nel.org>, 
	linux-phy@...ts.infradead.org, Neil Armstrong <neil.armstrong@...aro.org>, 
	freedreno@...ts.freedesktop.org, Douglas Anderson <dianders@...omium.org>, 
	Abhinav Kumar <quic_abhinavk@...cinc.com>
Subject: Re: [PATCH] phy: qcom: qmp-combo: Fix VCO div offset on v3

On Fri, 5 Apr 2024 at 02:43, Stephen Boyd <swboyd@...omium.org> wrote:
>
> Commit ec17373aebd0 ("phy: qcom: qmp-combo: extract common function to
> setup clocks") changed the offset that is used to write to
> DP_PHY_VCO_DIV from QSERDES_V3_DP_PHY_VCO_DIV to
> QSERDES_V4_DP_PHY_VCO_DIV. Unfortunately, this offset is different
> between v3 and v4 phys:
>
>  #define QSERDES_V3_DP_PHY_VCO_DIV                 0x064
>  #define QSERDES_V4_DP_PHY_VCO_DIV                 0x070
>
> meaning that we write the wrong register on v3 phys now. Add another
> generic register to 'regs' and use it here instead of a version specific
> define to fix this.
>
> This was discovered after Abhinav looked over register dumps with me
> from sc7180 Trogdor devices that started failing to light up the
> external display with v6.6 based kernels. It turns out that some
> monitors are very specific about their link clk frequency and if the
> default power on reset value is still there the monitor will show a
> blank screen or a garbled display. Other monitors are perfectly happy to
> get a bad clock signal.
>
> Cc: Douglas Anderson <dianders@...omium.org>
> Cc: Abhinav Kumar <quic_abhinavk@...cinc.com>
> Cc: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> Fixes: ec17373aebd0 ("phy: qcom: qmp-combo: extract common function to setup clocks")
> Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> ---
>  drivers/phy/qualcomm/phy-qcom-qmp-combo.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>

-- 
With best wishes
Dmitry