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From:   Robert Foss <robert.foss@linaro.org>
Date:   Thu, 29 Jul 2021 13:48:35 +0200
Message-ID: <CAG3jFyvwTY8azFVcHnSwgSe++ZNEfMvhbgROsLhpY00hwg5ikA@mail.gmail.com>
Subject: Re: [PATCH 3/6] drm/bridge: ti-sn65dsi86: Add some 100 us delays
To:     Douglas Anderson <dianders@chromium.org>
Cc:     dri-devel <dri-devel@lists.freedesktop.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        MSM <linux-arm-msm@vger.kernel.org>,
        Andrzej Hajda <a.hajda@samsung.com>,
        Sam Ravnborg <sam@ravnborg.org>,
        David Airlie <airlied@linux.ie>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Daniel Vetter <daniel@ffwll.ch>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        Jonas Karlman <jonas@kwiboo.se>,
        Neil Armstrong <narmstrong@baylibre.com>,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Maxime Ripard <mripard@kernel.org>,
        Linus Walleij <linus.walleij@linaro.org>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        rajeevny@codeaurora.org, Lyude Paul <lyude@redhat.com>,
        Thierry Reding <thierry.reding@gmail.com>,
        Steev Klimaszewski <steev@kali.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
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Precedence: bulk

Hey Doug,

Thanks for submitting this.

On Wed, 28 Jul 2021 at 18:46, Douglas Anderson <dianders@chromium.org> wrote:
>
> The manual has always said that we need 100 us delays in a few
> places. Though it hasn't seemed to be a big deal to skip these, let's
> add them in case it makes something happier.
>
> NOTE: this fixes no known issues but it seems good to make it right.
>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
>
>  drivers/gpu/drm/bridge/ti-sn65dsi86.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> index 5e932070a1c3..cd0fccdd8dfd 100644
> --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> @@ -307,6 +307,9 @@ static int __maybe_unused ti_sn65dsi86_resume(struct device *dev)
>                 return ret;
>         }
>
> +       /* td2: min 100 us after regulators before enabling the GPIO */
> +       usleep_range(100, 110);
> +
>         gpiod_set_value(pdata->enable_gpio, 1);
>
>         /*
> @@ -1096,6 +1099,9 @@ static void ti_sn_bridge_pre_enable(struct drm_bridge *bridge)
>
>         if (!pdata->refclk)
>                 ti_sn65dsi86_enable_comms(pdata);
> +
> +       /* td7: min 100 us after enable before DSI data */
> +       usleep_range(100, 110);
>  }
>
>  static void ti_sn_bridge_post_disable(struct drm_bridge *bridge)
> --
> 2.32.0.432.gabb21c7263-goog
>

Acked-by: Robert Foss <robert.foss@linaro.org>