linux-kernel - Re: [PATCH v4] drm/msm/dp: power off DP phy at suspend

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Message-ID: <CAE-0n516E_x+h2BFze0mozjdpwqa3_kb10cKWdcFURXkNj8k6w@mail.gmail.com>
Date:   Wed, 2 Jun 2021 23:03:07 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Kuogee Hsieh <khsieh@...eaurora.org>, agross@...nel.org,
        bjorn.andersson@...aro.org, robdclark@...il.com, sean@...rly.run,
        vkoul@...nel.org
Cc:     abhinavk@...eaurora.org, aravindh@...eaurora.org,
        freedreno@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] drm/msm/dp: power off DP phy at suspend

Quoting Kuogee Hsieh (2021-06-02 09:43:05)
> Normal DP suspend operation contains two steps, display off followed
> by dp suspend, to complete system wide suspending cycle if display is
> up at that time. In this case, DP phy will be powered off at display
> off. However there is an exception case that depending on the timing
> of dongle plug in during system wide suspending, sometimes display off
> procedure may be skipped and dp suspend was called directly. In this
> case, dp phy is stay at powered on (phy->power_count = 1) so that at
> next resume dp driver crash at main link clock enable due to phy is
> not physically powered on. This patch will call dp_ctrl_off_link_stream()
> to tear down main link and power off phy at dp_pm_suspend() if main link
> had been brought up.
>
> Changes in V2:
> -- stashed changes into dp_ctrl.c
> -- add is_phy_on to monitor phy state
>
> Changes in V3:
> -- delete is_phy_on
> -- call dp_ctrl_off_link_stream() from dp_pm_suspend()
>
> Changes in V4:
> -- delete changes made at dp_power.c
> -- move main link status checking to dp_pm_suspend
>
> Fixes: 0114f31a2903 ("drm/msm/dp: handle irq_hpd with sink_count = 0 correctly)

This should be 8dbde399044b