linux-kernel - Re: [PATCH] drm/msm/dp: add support of HBR3 link rate

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Date:   Wed, 17 Feb 2021 09:36:18 -0800
From:   Stephen Boyd <swboyd@...omium.org>
To:     Kuogee Hsieh <khsieh@...eaurora.org>, robdclark@...il.com,
        sean@...rly.run, Vinod Koul <vkoul@...nel.org>
Cc:     tanmay@...eaurora.org, abhinavk@...eaurora.org,
        aravindh@...eaurora.org, khsieh@...eaurora.org, airlied@...ux.ie,
        daniel@...ll.ch, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/msm/dp: add support of HBR3 link rate

Quoting Kuogee Hsieh (2021-02-17 08:58:42)
> Add hbr3_hbr2 voltage and pre-emphasis swing table to support
> HBR3 link rate
> 
> Signed-off-by: Kuogee Hsieh <khsieh@...eaurora.org>
> ---
>  drivers/gpu/drm/msm/dp/dp_panel.c   |  4 ----
>  drivers/phy/qualcomm/phy-qcom-qmp.c | 24 ++++++++++++++++++++++--

This spans to subsystems so at least you should run get_maintainers and
include phy maintainers. Maybe it should be split into two patches too
so it can go via different trees.

>  2 files changed, 22 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_panel.c b/drivers/gpu/drm/msm/dp/dp_panel.c
> index 9cc8166..63112fa 100644
> --- a/drivers/gpu/drm/msm/dp/dp_panel.c
> +++ b/drivers/gpu/drm/msm/dp/dp_panel.c
> @@ -76,10 +76,6 @@ static int dp_panel_read_dpcd(struct dp_panel *dp_panel)
>         if (link_info->num_lanes > dp_panel->max_dp_lanes)
>                 link_info->num_lanes = dp_panel->max_dp_lanes;
>  
> -       /* Limit support upto HBR2 until HBR3 support is added */
> -       if (link_info->rate >= (drm_dp_bw_code_to_link_rate(DP_LINK_BW_5_4)))
> -               link_info->rate = drm_dp_bw_code_to_link_rate(DP_LINK_BW_5_4);
> -
>         DRM_DEBUG_DP("version: %d.%d\n", major, minor);
>         DRM_DEBUG_DP("link_rate=%d\n", link_info->rate);
>         DRM_DEBUG_DP("lane_count=%d\n", link_info->num_lanes);
> diff --git a/drivers/phy/qualcomm/phy-qcom-qmp.c b/drivers/phy/qualcomm/phy-qcom-qmp.c
> index 0939a9e..cc5ef59 100644
> --- a/drivers/phy/qualcomm/phy-qcom-qmp.c
> +++ b/drivers/phy/qualcomm/phy-qcom-qmp.c
> @@ -2965,6 +2965,21 @@ static void qcom_qmp_phy_dp_aux_init(struct qmp_phy *qphy)
>                qphy->pcs + QSERDES_V3_DP_PHY_AUX_INTERRUPT_MASK);
>  }
>  
> +
> +static u8 const qmp_dp_v3_pre_emphasis_hbr3_hbr2[4][4] = {

Should be static const u8 qmp_dp...

> +        {0x00, 0x0C, 0x15, 0x1A},
> +        {0x02, 0x0E, 0x16, 0xFF},
> +        {0x02, 0x11, 0xFF, 0xFF},
> +        {0x04, 0xFF, 0xFF, 0xFF}
> +};
> +
> +static u8 const qmp_dp_v3_voltage_swing_hbr3_hbr2[4][4] = {

Same.

> +        {0x02, 0x12, 0x16, 0x1A},

Please add a space after { and before } and use lowercase hex to match
the qmp_dp_v3_pre_emphasis_hbr_rbr design.

> +        {0x09, 0x19, 0x1F, 0xFF},
> +        {0x10, 0x1F, 0xFF, 0xFF},
> +        {0x1F, 0xFF, 0xFF, 0xFF}
> +};
> +
>  static const u8 qmp_dp_v3_pre_emphasis_hbr_rbr[4][4] = {
>         { 0x00, 0x0c, 0x14, 0x19 },
>         { 0x00, 0x0b, 0x12, 0xff },
> @@ -3000,8 +3015,13 @@ static void qcom_qmp_phy_configure_dp_tx(struct qmp_phy *qphy)
>                 drvr_en = 0x10;
>         }
>  
> -       voltage_swing_cfg = qmp_dp_v3_voltage_swing_hbr_rbr[v_level][p_level];
> -       pre_emphasis_cfg = qmp_dp_v3_pre_emphasis_hbr_rbr[v_level][p_level];
> +       if (dp_opts->link_rate <= 2700) {
> +               voltage_swing_cfg = qmp_dp_v3_voltage_swing_hbr_rbr[v_level][p_level];
> +               pre_emphasis_cfg = qmp_dp_v3_pre_emphasis_hbr_rbr[v_level][p_level];
> +       } else {
> +               voltage_swing_cfg = qmp_dp_v3_voltage_swing_hbr3_hbr2[v_level][p_level];
> +               pre_emphasis_cfg = qmp_dp_v3_pre_emphasis_hbr3_hbr2[v_level][p_level];
> +       }