linux-kernel - Re: [RFT PATCH v2 1/3] drm/bridge: tc358762: Set pre_enable_prev

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Date:   Wed, 1 Feb 2023 09:51:06 +0000
From:   Dave Stevenson <dave.stevenson@...pberrypi.com>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     dri-devel@...ts.freedesktop.org, Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        freedreno@...ts.freedesktop.org,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Jonas Karlman <jonas@...boo.se>, linux-arm-msm@...r.kernel.org,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <robert.foss@...aro.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Vinod Koul <vkoul@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Sean Paul <sean@...rly.run>, linux-kernel@...r.kernel.org
Subject: Re: [RFT PATCH v2 1/3] drm/bridge: tc358762: Set pre_enable_prev_first

On Tue, 31 Jan 2023 at 22:22, Douglas Anderson <dianders@...omium.org> wrote:
>
> Set the "pre_enable_prev_first" as provided by commit 4fb912e5e190
> ("drm/bridge: Introduce pre_enable_prev_first to alter bridge init
> order"). This should allow us to revert commit ec7981e6c614
> ("drm/msm/dsi: don't powerup at modeset time for parade-ps8640") and
> commit 7d8e9a90509f ("drm/msm/dsi: move DSI host powerup to modeset
> time").

I see no reference in the TC358762 datasheet to requiring the DSI
interface to be in any particular state.
However, setting this flag does mean that the DSI host doesn't need to
power up and down for each host_transfer request from
tc358762_pre_enable/tc358762_init, so on that basis I'm good with it.

Reviewed-by: Dave Stevenson <dave.stevenson@...pberrypi.com>

> Cc: Dave Stevenson <dave.stevenson@...pberrypi.com>
> Cc: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> Cc: Abhinav Kumar <quic_abhinavk@...cinc.com>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
>
> (no changes since v1)
>
>  drivers/gpu/drm/bridge/tc358762.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/gpu/drm/bridge/tc358762.c b/drivers/gpu/drm/bridge/tc358762.c
> index 0b6a28436885..77f7f7f54757 100644
> --- a/drivers/gpu/drm/bridge/tc358762.c
> +++ b/drivers/gpu/drm/bridge/tc358762.c
> @@ -229,6 +229,7 @@ static int tc358762_probe(struct mipi_dsi_device *dsi)
>         ctx->bridge.funcs = &tc358762_bridge_funcs;
>         ctx->bridge.type = DRM_MODE_CONNECTOR_DPI;
>         ctx->bridge.of_node = dev->of_node;
> +       ctx->bridge.pre_enable_prev_first = true;
>
>         drm_bridge_add(&ctx->bridge);
>
> --
> 2.39.1.456.gfc5497dd1b-goog
>