linux-kernel - Re: [PATCH] drm/msm/dp: keep aux channel up when power of dp phy

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Date:   Thu, 27 May 2021 00:29:30 -0400
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] drm/msm/dp: keep aux channel up when power of dp phy

General note, please Cc dri-devel on freedreno driver patches.

Quoting Kuogee Hsieh (2021-05-26 16:49:49)
> Aux channel is used to perform management function and should be
> running in parallel with main link. Therefore should only power
> down main link and keep aux channel running when power down phy.
>
> Signed-off-by: Kuogee Hsieh <khsieh@...eaurora.org>
> ---

Does this supersede the previous patch[1] or is it in addition to?

[1] https://lore.kernel.org/r/1622052503-21158-1-git-send-email-khsieh@codeaurora.org

>  drivers/gpu/drm/msm/dp/dp_ctrl.c    |  4 ----
>  drivers/phy/qualcomm/phy-qcom-qmp.c | 11 +++++++++--
>  2 files changed, 9 insertions(+), 6 deletions(-)

Given that it touches two subsystems the merge path is questionable.

>
> diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> index 5115c05..5f93c64 100644
> --- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
> +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> @@ -1844,10 +1844,6 @@ int dp_ctrl_off_link_stream(struct dp_ctrl *dp_ctrl)
>
>         phy_power_off(phy);
>
> -       /* aux channel down, reinit phy */
> -       phy_exit(phy);
> -       phy_init(phy);
> -
>         DRM_DEBUG_DP("DP off link/stream done\n");
>         return ret;
>  }
> diff --git a/drivers/phy/qualcomm/phy-qcom-qmp.c b/drivers/phy/qualcomm/phy-qcom-qmp.c
> index b122e63..567e32e 100644
> --- a/drivers/phy/qualcomm/phy-qcom-qmp.c
> +++ b/drivers/phy/qualcomm/phy-qcom-qmp.c
> @@ -3214,12 +3214,19 @@ static int qcom_qmp_phy_power_off(struct phy *phy)
>  {
>         struct qmp_phy *qphy = phy_get_drvdata(phy);
>         const struct qmp_phy_cfg *cfg = qphy->cfg;
> +       u32 val;
>
>         clk_disable_unprepare(qphy->pipe_clk);
>
>         if (cfg->type == PHY_TYPE_DP) {
> -               /* Assert DP PHY power down */
> -               writel(DP_PHY_PD_CTL_PSR_PWRDN, qphy->pcs + QSERDES_V3_DP_PHY_PD_CTL);
> +               /*
> +                * Assert DP PHY LANE_0_1, LANE_2_3, PSR power down
> +                * keep aux channel up

Maybe say "keep aux channel up until phy_exit() is called" so we know
how long it is supposed to stay on. And just to confirm, it is on in
phy_init(), right?

> +                */
> +               val = DP_PHY_PD_CTL_PWRDN | DP_PHY_PD_CTL_AUX_PWRDN |
> +                       DP_PHY_PD_CTL_PLL_PWRDN | DP_PHY_PD_CTL_DP_CLAMP_EN |
> +                       DP_PHY_PD_CTL_PSR_PWRDN;
> +               writel(val, qphy->pcs + QSERDES_V3_DP_PHY_PD_CTL);
>         } else {
>                 /* PHY reset */
>                 if (!cfg->no_pcs_sw_reset)