linux-kernel - Re: [PATCH v2] drm/msm/dp: add support of tps4 (training pattern 4) for HBR3

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Message-ID: <CAE-0n50QyX0YsvZbAfi_bL+4-jQrdB7FFUPL3pksLW_9Xzb9hg@mail.gmail.com>
Date:   Wed, 5 Jan 2022 13:13:55 -0800
From:   Stephen Boyd <swboyd@...omium.org>
To:     Kuogee Hsieh <quic_khsieh@...cinc.com>, agross@...nel.org,
        airlied@...ux.ie, bjorn.andersson@...aro.org, daniel@...ll.ch,
        dmitry.baryshkov@...aro.org, robdclark@...il.com, sean@...rly.run,
        vkoul@...nel.org
Cc:     quic_abhinavk@...cinc.com, aravindh@...eaurora.org,
        quic_sbillaka@...cinc.com, freedreno@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Kuogee Hsieh <khsieh@...eaurora.org>
Subject: Re: [PATCH v2] drm/msm/dp: add support of tps4 (training pattern 4)
 for HBR3

Quoting Kuogee Hsieh (2021-12-29 10:15:45)
> diff --git a/drivers/gpu/drm/msm/dp/dp_catalog.h b/drivers/gpu/drm/msm/dp/dp_catalog.h
> index 6965afa..7dea101 100644
> --- a/drivers/gpu/drm/msm/dp/dp_catalog.h
> +++ b/drivers/gpu/drm/msm/dp/dp_catalog.h
> @@ -94,7 +94,7 @@ void dp_catalog_ctrl_mainlink_ctrl(struct dp_catalog *dp_catalog, bool enable);
>  void dp_catalog_ctrl_config_misc(struct dp_catalog *dp_catalog, u32 cc, u32 tb);
>  void dp_catalog_ctrl_config_msa(struct dp_catalog *dp_catalog, u32 rate,
>                                 u32 stream_rate_khz, bool fixed_nvid);
> -int dp_catalog_ctrl_set_pattern(struct dp_catalog *dp_catalog, u32 pattern);
> +int dp_catalog_ctrl_set_pattern_state_bit(struct dp_catalog *dp_catalog, u32 pattern);
>  void dp_catalog_ctrl_reset(struct dp_catalog *dp_catalog);
>  bool dp_catalog_ctrl_mainlink_ready(struct dp_catalog *dp_catalog);
>  void dp_catalog_ctrl_enable_irq(struct dp_catalog *dp_catalog, bool enable);
> diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> index 39558a2..da6c083 100644
> --- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
> +++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
> @@ -1078,12 +1078,13 @@ static int dp_ctrl_link_train_1(struct dp_ctrl_private *ctrl,
>         int tries, old_v_level, ret = 0;
>         u8 link_status[DP_LINK_STATUS_SIZE];
>         int const maximum_retries = 4;
> +       char state_ctrl_bit = 1;
>
>         dp_catalog_ctrl_state_ctrl(ctrl->catalog, 0);
>
>         *training_step = DP_TRAINING_1;
>
> -       ret = dp_catalog_ctrl_set_pattern(ctrl->catalog, DP_TRAINING_PATTERN_1);
> +       ret = dp_catalog_ctrl_set_pattern_state_bit(ctrl->catalog, state_ctrl_bit);

Why not inline 'state_ctrl_bit' value of 1 here?

>         if (ret)
>                 return ret;
>         dp_ctrl_train_pattern_set(ctrl, DP_TRAINING_PATTERN_1 |
> @@ -1181,7 +1182,7 @@ static int dp_ctrl_link_train_2(struct dp_ctrl_private *ctrl,
>                         int *training_step)
>  {
>         int tries = 0, ret = 0;
> -       char pattern;
> +       char pattern, state_ctrl_bit;

Why is 'state_ctrl_bit' a char when the function it's passed to takes a
u32? Please be consistent with types. It would be good to make 'pattern'
into a u8 as well instead of a char to be similarly consistent.

>         int const maximum_retries = 5;
>         u8 link_status[DP_LINK_STATUS_SIZE];
>
> @@ -1189,12 +1190,20 @@ static int dp_ctrl_link_train_2(struct dp_ctrl_private *ctrl,
>
>         *training_step = DP_TRAINING_2;
>
> -       if (drm_dp_tps3_supported(ctrl->panel->dpcd))
> +       if (drm_dp_tps4_supported(ctrl->panel->dpcd)) {
> +               pattern = DP_TRAINING_PATTERN_4;
> +               state_ctrl_bit = 4;
> +       }
> +       else if (drm_dp_tps3_supported(ctrl->panel->dpcd)) {
>                 pattern = DP_TRAINING_PATTERN_3;
> -       else
> +               state_ctrl_bit = 3;
> +       }
> +       else {
>                 pattern = DP_TRAINING_PATTERN_2;
> +               state_ctrl_bit = 2;
> +       }
>
> -       ret = dp_catalog_ctrl_set_pattern(ctrl->catalog, pattern);
> +       ret = dp_catalog_ctrl_set_pattern_state_bit(ctrl->catalog, state_ctrl_bit);
>         if (ret)
>                 return ret;
>