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Subject: Re: [PATCH v2] drm/vc4: Make DSI call into the bridge after the DSI
 link is enabled.
To:     Eric Anholt <eric@anholt.net>, dri-devel@lists.freedesktop.org
Cc:     linux-kernel@vger.kernel.org
From:   Andrzej Hajda <a.hajda@samsung.com>
Date:   Thu, 28 Jun 2018 14:41:24 +0200
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On 22.06.2018 01:17, Eric Anholt wrote:
> This allows panels or bridges that need to send DSI commands during
> pre_enable() to successfully send them.  We delay DISP0 (aka the
> actual display) enabling until after pre_enable so that pixels aren't
> streaming before then.
>
> v2: Just clear out the encoder->bridge value to disable the midlayer
>     calls (idea by Andrzej Hajda).
>
> Signed-off-by: Eric Anholt <eric@anholt.net>
> Cc: Andrzej Hajda <a.hajda@samsung.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>

 --
Regards
Andrzej
> ---
>  drivers/gpu/drm/vc4/vc4_dsi.c | 42 ++++++++++++++++++++++-------------
>  1 file changed, 27 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c
> index 8aa897835118..9c8e89372d1c 100644
> --- a/drivers/gpu/drm/vc4/vc4_dsi.c
> +++ b/drivers/gpu/drm/vc4/vc4_dsi.c
> @@ -814,7 +814,9 @@ static void vc4_dsi_encoder_disable(struct drm_encoder *encoder)
>  	struct vc4_dsi *dsi = vc4_encoder->dsi;
>  	struct device *dev = &dsi->pdev->dev;
>  
> +	drm_bridge_disable(dsi->bridge);
>  	vc4_dsi_ulps(dsi, true);
> +	drm_bridge_post_disable(dsi->bridge);
>  
>  	clk_disable_unprepare(dsi->pll_phy_clock);
>  	clk_disable_unprepare(dsi->escape_clock);
> @@ -1089,21 +1091,6 @@ static void vc4_dsi_encoder_enable(struct drm_encoder *encoder)
>  	/* Display reset sequence timeout */
>  	DSI_PORT_WRITE(PR_TO_CNT, 100000);
>  
> -	if (dsi->mode_flags & MIPI_DSI_MODE_VIDEO) {
> -		DSI_PORT_WRITE(DISP0_CTRL,
> -			       VC4_SET_FIELD(dsi->divider,
> -					     DSI_DISP0_PIX_CLK_DIV) |
> -			       VC4_SET_FIELD(dsi->format, DSI_DISP0_PFORMAT) |
> -			       VC4_SET_FIELD(DSI_DISP0_LP_STOP_PERFRAME,
> -					     DSI_DISP0_LP_STOP_CTRL) |
> -			       DSI_DISP0_ST_END |
> -			       DSI_DISP0_ENABLE);
> -	} else {
> -		DSI_PORT_WRITE(DISP0_CTRL,
> -			       DSI_DISP0_COMMAND_MODE |
> -			       DSI_DISP0_ENABLE);
> -	}
> -
>  	/* Set up DISP1 for transferring long command payloads through
>  	 * the pixfifo.
>  	 */
> @@ -1128,6 +1115,25 @@ static void vc4_dsi_encoder_enable(struct drm_encoder *encoder)
>  
>  	vc4_dsi_ulps(dsi, false);
>  
> +	drm_bridge_pre_enable(dsi->bridge);
> +
> +	if (dsi->mode_flags & MIPI_DSI_MODE_VIDEO) {
> +		DSI_PORT_WRITE(DISP0_CTRL,
> +			       VC4_SET_FIELD(dsi->divider,
> +					     DSI_DISP0_PIX_CLK_DIV) |
> +			       VC4_SET_FIELD(dsi->format, DSI_DISP0_PFORMAT) |
> +			       VC4_SET_FIELD(DSI_DISP0_LP_STOP_PERFRAME,
> +					     DSI_DISP0_LP_STOP_CTRL) |
> +			       DSI_DISP0_ST_END |
> +			       DSI_DISP0_ENABLE);
> +	} else {
> +		DSI_PORT_WRITE(DISP0_CTRL,
> +			       DSI_DISP0_COMMAND_MODE |
> +			       DSI_DISP0_ENABLE);
> +	}
> +
> +	drm_bridge_enable(dsi->bridge);
> +
>  	if (debug_dump_regs) {
>  		DRM_INFO("DSI regs after:\n");
>  		vc4_dsi_dump_regs(dsi);
> @@ -1639,6 +1645,12 @@ static int vc4_dsi_bind(struct device *dev, struct device *master, void *data)
>  		dev_err(dev, "bridge attach failed: %d\n", ret);
>  		return ret;
>  	}
> +	/* Disable the atomic helper calls into the bridge.  We
> +	 * manually call the bridge pre_enable / enable / etc. calls
> +	 * from our driver, since we need to sequence them within the
> +	 * encoder's enable/disable paths.
> +	 */
> +	dsi->encoder->bridge = NULL;
>  
>  	pm_runtime_enable(dev);
>