linux-kernel - Re: [PATCH v2 1/2] drm/msm/dp: Add support for SC7280 eDP

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Date:   Thu, 21 Oct 2021 11:02:22 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Sankeerth Billakanti <quic_sbillaka@...cinc.com>,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Sankeerth Billakanti <sbillaka@...eaurora.org>,
        robdclark@...il.com, seanpaul@...omium.org,
        kalyan_t@...eaurora.org, abhinavk@...eaurora.org,
        dianders@...omium.org, khsieh@...eaurora.org,
        mkrishn@...eaurora.org
Subject: Re: [PATCH v2 1/2] drm/msm/dp: Add support for SC7280 eDP

Quoting Sankeerth Billakanti (2021-10-20 05:14:10)
> diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> index 62e75dc..9fea49c 100644
> --- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
> +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> @@ -1238,9 +1240,21 @@ static int dp_ctrl_link_train(struct dp_ctrl_private *ctrl,
>         link_info.capabilities = DP_LINK_CAP_ENHANCED_FRAMING;
>
>         dp_aux_link_configure(ctrl->aux, &link_info);
> +
> +       if (dpcd[DP_MAX_DOWNSPREAD] & DP_MAX_DOWNSPREAD_0_5) {

Please add a static inline macro in include/drm/drm_dp_helper.h that
makes this more readable. Something similar to drm_dp_is_branch() but
with a human readable replacement for "is_branch". Maybe drm_dp_ssc()?

> +               ssc = DP_SPREAD_AMP_0_5;
> +               drm_dp_dpcd_write(ctrl->aux, DP_DOWNSPREAD_CTRL, &ssc, 1);
> +       }
> +
>         drm_dp_dpcd_write(ctrl->aux, DP_MAIN_LINK_CHANNEL_CODING_SET,
>                                 &encoding, 1);
>
> +       if (dpcd[DP_EDP_CONFIGURATION_CAP] & DP_ALTERNATE_SCRAMBLER_RESET_CAP) {

And this one already has a helper,
drm_dp_alternate_scrambler_reset_cap().

> +               assr = DP_ALTERNATE_SCRAMBLER_RESET_ENABLE;
> +               drm_dp_dpcd_write(ctrl->aux, DP_EDP_CONFIGURATION_SET,
> +                               &assr, 1);
> +       }
> +
>         ret = dp_ctrl_link_train_1(ctrl, training_step);
>         if (ret) {
>                 DRM_ERROR("link training #1 failed. ret=%d\n", ret);
> @@ -1312,9 +1326,11 @@ static int dp_ctrl_enable_mainlink_clocks(struct dp_ctrl_private *ctrl)
>         struct dp_io *dp_io = &ctrl->parser->io;
>         struct phy *phy = dp_io->phy;
>         struct phy_configure_opts_dp *opts_dp = &dp_io->phy_opts.dp;
> +       const u8 *dpcd = ctrl->panel->dpcd;
>
>         opts_dp->lanes = ctrl->link->link_params.num_lanes;
>         opts_dp->link_rate = ctrl->link->link_params.rate / 100;
> +       opts_dp->ssc = dpcd[DP_MAX_DOWNSPREAD] & DP_MAX_DOWNSPREAD_0_5;
>         dp_ctrl_set_clock_rate(ctrl, DP_CTRL_PM, "ctrl_link",
>                                         ctrl->link->link_params.rate * 1000);
>
> @@ -1406,7 +1422,7 @@ void dp_ctrl_host_deinit(struct dp_ctrl *dp_ctrl)
>
>  static bool dp_ctrl_use_fixed_nvid(struct dp_ctrl_private *ctrl)
>  {
> -       u8 *dpcd = ctrl->panel->dpcd;
> +       const u8 *dpcd = ctrl->panel->dpcd;
>
>         /*
>          * For better interop experience, used a fixed NVID=0x8000
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index c867745..c16311b 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -144,8 +144,16 @@ static const struct msm_dp_config sc8180x_dp_cfg = {
>         .num_descs = 3,
>  };
>
> +static const struct msm_dp_config sc7280_dp_cfg = {
> +       .descs = (struct msm_dp_desc[]) {

const

> +               { .io_start = 0x0aea0000, .connector_type = DRM_MODE_CONNECTOR_eDP },
> +       },
> +       .num_descs = 1,
> +};
> +
>  static const struct of_device_id dp_dt_match[] = {
>         { .compatible = "qcom,sc7180-dp", .data = &sc7180_dp_cfg },
> +       { .compatible = "qcom,sc7280-edp", .data = &sc7280_dp_cfg },
>         { .compatible = "qcom,sc8180x-dp", .data = &sc8180x_dp_cfg },
>         { .compatible = "qcom,sc8180x-edp", .data = &sc8180x_dp_cfg },
>         {}
> @@ -1440,7 +1448,7 @@ void msm_dp_irq_postinstall(struct msm_dp *dp_display)
>
>         dp_hpd_event_setup(dp);
>
> -       dp_add_event(dp, EV_HPD_INIT_SETUP, 0, 100);
> +       dp_add_event(dp, EV_HPD_INIT_SETUP, 0, 1);

This has no explanation. What is it?