linux-kernel - Re: [PATCH 4/8] drm/mediatek: dsi: add pdata variable to start clk in HS mode

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Date:   Thu, 22 Oct 2020 01:07:04 +0800
From:   Chun-Kuang Hu <chunkuang.hu@...nel.org>
To:     Fabien Parent <fparent@...libre.com>
Cc:     "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>
Subject: Re: [PATCH 4/8] drm/mediatek: dsi: add pdata variable to start clk in
 HS mode

Hi, Fabien:

Fabien Parent <fparent@...libre.com> 於 2020年10月21日 週三 上午1:43寫道：
>
> On MT8167, DSI seems to work fine only if we start the clk in HS mode.
> If we don't start the clk in HS but try to switch later to HS, the
> display does not work.
>
> This commit adds a platform data variable to be used to start the
> DSI clk in HS mode at power on.

This patch looks like a hack patch. If you cowork with Mediatek,
please find out the correct solution or give a reasonable explanation.
If you could not get help from Mediatek, I would wait for comment on
this patch.

Regards,
Chun-Kuang.

>
> Signed-off-by: Fabien Parent <fparent@...libre.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_dsi.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index 4a188a942c38..461643c05689 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> @@ -175,6 +175,7 @@ struct mtk_dsi_driver_data {
>         const u32 reg_cmdq_off;
>         bool has_shadow_ctl;
>         bool has_size_ctl;
> +       bool use_hs_on_power_on;
>  };
>
>  struct mtk_dsi {
> @@ -671,7 +672,7 @@ static int mtk_dsi_poweron(struct mtk_dsi *dsi)
>
>         mtk_dsi_clk_ulp_mode_leave(dsi);
>         mtk_dsi_lane0_ulp_mode_leave(dsi);
> -       mtk_dsi_clk_hs_mode(dsi, 0);
> +       mtk_dsi_clk_hs_mode(dsi, !!dsi->driver_data->use_hs_on_power_on);
>
>         return 0;
>  err_disable_engine_clk:
> --
> 2.28.0
>