linux-kernel - Re: [PATCH v1] drm/msm/dp: do not reinitialize phy unless retry during link training

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Message-ID: <ZSkysaMcOQO89zpd@hovoldconsulting.com>
Date:   Fri, 13 Oct 2023 14:06:09 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Kuogee Hsieh <quic_khsieh@...cinc.com>
Cc:     robdclark@...il.com, sean@...rly.run, swboyd@...omium.org,
        dianders@...omium.org, vkoul@...nel.org, daniel@...ll.ch,
        airlied@...il.com, agross@...nel.org, dmitry.baryshkov@...aro.org,
        andersson@...nel.org, marijn.suijten@...ainline.org,
        quic_abhinavk@...cinc.com, quic_jesszhan@...cinc.com,
        quic_sbillaka@...cinc.com, freedreno@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] drm/msm/dp: do not reinitialize phy unless retry
 during link training

On Tue, Oct 03, 2023 at 11:10:59AM +0200, Johan Hovold wrote:
> On Tue, Aug 08, 2023 at 03:19:50PM -0700, Kuogee Hsieh wrote:
> > DP PHY re-initialization done using dp_ctrl_reinitialize_mainlink() will
> > cause PLL unlocked initially and then PLL gets locked at the end of
> > initialization. PLL_UNLOCKED interrupt will fire during this time if the
> > interrupt mask is enabled.
> > However currently DP driver link training implementation incorrectly
> > re-initializes PHY unconditionally during link training as the PHY was
> > already configured in dp_ctrl_enable_mainlink_clocks().
> > 
> > Fix this by re-initializing the PHY only if the previous link training
> > failed.
> > 
> > [drm:dp_aux_isr] *ERROR* Unexpected DP AUX IRQ 0x01000000 when not busy
> > 
> > Fixes: c943b4948b58 ("drm/msm/dp: add displayPort driver support")
> > Closes: https://gitlab.freedesktop.org/drm/msm/-/issues/30
> > Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
> 
> This fixes the above warning and avoids the unnecessary PHY power-off
> and power-on during boot of the ThinkPad X13s:
> 
> Reviewed-by: Johan Hovold <johan+linaro@...nel.org>
> Tested-by: Johan Hovold <johan+linaro@...nel.org>
> 
> I guess this one should go to stable as well:
> 
> Cc: stable@...r.kernel.org	# 5.10
> 
> Is anyone planning on getting this fixed in 6.6-rc? I noticed that this
> one still hasn't shown up linux-next.

For the record, this one showed up in a PR from Rob and has now been
forwarded to Linus.

No stable tag included, but I guess we can ping the stable team unless
AUTOSEL picks this up.

Johan