linux-kernel - Re: [PATCH v1 4/5] drm/bridge: tc358768: Disable non-continuous clock mode

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Date:   Tue, 19 Oct 2021 11:37:06 +0200
From:   Robert Foss <robert.foss@...aro.org>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Maxim Schwalm <maxim.schwalm@...il.com>,
        Andreas Westman Dorcsak <hedmoo@...oo.com>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-tegra@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 4/5] drm/bridge: tc358768: Disable non-continuous clock mode

On Sun, 3 Oct 2021 at 01:35, Dmitry Osipenko <digetx@...il.com> wrote:
>
> Non-continuous clock mode doesn't work because driver doesn't support it
> properly. The bridge driver programs wrong bitfields that are required by
> the non-continuous mode (BTACNTRL1 register bitfields are swapped in the
> code), but fixing them doesn't help.
>
> Display panel of ASUS Transformer TF700T tablet supports non-continuous
> mode and display doesn't work at all using that mode. There are no
> device-trees that are actively using this DSI bridge in upstream yet,
> so clearly the broken mode wasn't ever tested properly. It's a bit too
> difficult to get LP mode working, hence let's disable the offending mode
> for now and fall back to continuous mode.
>
> Tested-by: Andreas Westman Dorcsak <hedmoo@...oo.com> # Asus TF700T
> Tested-by: Maxim Schwalm <maxim.schwalm@...il.com> #TF700T
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  drivers/gpu/drm/bridge/tc358768.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/tc358768.c b/drivers/gpu/drm/bridge/tc358768.c
> index 5b3f8723bd3d..cfceba5ef3b8 100644
> --- a/drivers/gpu/drm/bridge/tc358768.c
> +++ b/drivers/gpu/drm/bridge/tc358768.c
> @@ -631,6 +631,7 @@ static void tc358768_bridge_pre_enable(struct drm_bridge *bridge)
>  {
>         struct tc358768_priv *priv = bridge_to_tc358768(bridge);
>         struct mipi_dsi_device *dsi_dev = priv->output.dev;
> +       unsigned long mode_flags = dsi_dev->mode_flags;
>         u32 val, val2, lptxcnt, hact, data_type;
>         const struct drm_display_mode *mode;
>         u32 dsibclk_nsk, dsiclk_nsk, ui_nsk, phy_delay_nsk;
> @@ -638,6 +639,11 @@ static void tc358768_bridge_pre_enable(struct drm_bridge *bridge)
>         const u32 internal_delay = 40;
>         int ret, i;
>
> +       if (mode_flags & MIPI_DSI_CLOCK_NON_CONTINUOUS) {
> +               dev_warn_once(priv->dev, "Non-continuous mode unimplemented, falling back to continuous\n");
> +               mode_flags &= ~MIPI_DSI_CLOCK_NON_CONTINUOUS;
> +       }
> +
>         tc358768_hw_enable(priv);
>
>         ret = tc358768_sw_reset(priv);
> @@ -776,7 +782,7 @@ static void tc358768_bridge_pre_enable(struct drm_bridge *bridge)
>                 val |= BIT(i + 1);
>         tc358768_write(priv, TC358768_HSTXVREGEN, val);
>
> -       if (!(dsi_dev->mode_flags & MIPI_DSI_CLOCK_NON_CONTINUOUS))
> +       if (!(mode_flags & MIPI_DSI_CLOCK_NON_CONTINUOUS))
>                 tc358768_write(priv, TC358768_TXOPTIONCNTRL, 0x1);
>
>         /* TXTAGOCNT[26:16] RXTASURECNT[10:0] */
> @@ -864,7 +870,7 @@ static void tc358768_bridge_pre_enable(struct drm_bridge *bridge)
>         if (!(dsi_dev->mode_flags & MIPI_DSI_MODE_LPM))
>                 val |= TC358768_DSI_CONTROL_TXMD;
>
> -       if (!(dsi_dev->mode_flags & MIPI_DSI_CLOCK_NON_CONTINUOUS))
> +       if (!(mode_flags & MIPI_DSI_CLOCK_NON_CONTINUOUS))
>                 val |= TC358768_DSI_CONTROL_HSCKMD;
>
>         if (dsi_dev->mode_flags & MIPI_DSI_MODE_NO_EOT_PACKET)
> --

Reviewed-by: Robert Foss <robert.foss@...aro.org>