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

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Date:   Wed, 27 Oct 2021 00:31:54 +0530
From:   sbillaka@...eaurora.org
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     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,
        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

Hi Stephen,

On 2021-10-21 23:32, Stephen Boyd wrote:
> 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()?
> 
Okay, I will add a macro, drm_dp_max_downspread (to be consistent with 
the spec and other macros in the file) in drm_dp_helper.h file.

>> +               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().
> 
Okay, I will use that.

>> +               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
> 
Will add it.

>> +               { .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?
Will add explanation for it as a comment.