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Date:   Sat, 17 Jun 2023 19:35:53 +0200
From:   Sam Ravnborg <sam@ravnborg.org>
To:     =?utf-8?Q?Ond=C5=99ej?= Jirman <megi@xff.cz>
Cc:     linux-rockchip@lists.infradead.org,
        Neil Armstrong <neil.armstrong@linaro.org>,
        Robert Foss <rfoss@kernel.org>,
        Jonas Karlman <jonas@kwiboo.se>,
        "open list:DRM DRIVERS" <dri-devel@lists.freedesktop.org>,
        open list <linux-kernel@vger.kernel.org>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        Andrzej Hajda <andrzej.hajda@intel.com>
Subject: Re: [PATCH] drm: bridge: dw-mipi-dsi: Fix enable/disable of DSI
 controller
Message-ID: <20230617173553.GA1843063@ravnborg.org>
References: <20230617150643.1808409-1-megi@xff.cz>
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Hi Ondřej,

On Sat, Jun 17, 2023 at 05:06:33PM +0200, Ondřej Jirman wrote:
> From: Ondrej Jirman <megi@xff.cz>
> 
> Before this patch, booting to Linux VT and doing a simple:
> 
>   echo 2 > /sys/class/graphics/fb0/blank
>   echo 0 > /sys/class/graphics/fb0/blank
> 
> would result in failures to re-enable the panel. Mode set callback is
> called only once during boot in this scenario, while calls to
> enable/disable callbacks are balanced afterwards. The driver doesn't
> work unless userspace calls modeset before enabling the CRTC/connector.
> 
> This patch moves enabling of the DSI host from mode_set into pre_enable
> callback, and removes some old hacks where this bridge driver is
> directly calling into other bridge driver's callbacks.
> 
> pre_enable_prev_first flag is set on the panel's bridge so that panel
> drivers will get their prepare function called between DSI host's
> pre_enable and enable callbacks, so that they get a chance to
> perform panel setup while DSI host is already enabled in command
> mode. Otherwise panel's prepare would be called before DSI host
> is enabled, and any DSI communication used in prepare callback
> would fail.
> 
> With all these changes, the enable/disable sequence is now well
> balanced, and host's and panel's callbacks are called in proper order
> documented in the drm_panel API documentation without needing the old
> hacks. (Mainly that panel->prepare is called when DSI host is ready to
> allow the panel driver to send DSI commands and vice versa during
> disable.)
> 
> Tested on Pinephone Pro. Trace of the callbacks follows.
> 
> Before:
> 
> [    1.253882] dw-mipi-dsi-rockchip ff960000.dsi: mode_set
> [    1.290732] panel-himax-hx8394 ff960000.dsi.0: prepare
> [    1.475576] dw-mipi-dsi-rockchip ff960000.dsi: enable
> [    1.475593] panel-himax-hx8394 ff960000.dsi.0: enable
> 
> echo 2 > /sys/class/graphics/fb0/blank
> 
> [   13.722799] panel-himax-hx8394 ff960000.dsi.0: disable
> [   13.774502] dw-mipi-dsi-rockchip ff960000.dsi: post_disable
> [   13.774526] panel-himax-hx8394 ff960000.dsi.0: unprepare
> 
> echo 0 > /sys/class/graphics/fb0/blank
> 
> [   17.735796] panel-himax-hx8394 ff960000.dsi.0: prepare
> [   17.923522] dw-mipi-dsi-rockchip ff960000.dsi: enable
> [   17.923540] panel-himax-hx8394 ff960000.dsi.0: enable
> [   17.944330] dw-mipi-dsi-rockchip ff960000.dsi: failed to write command FIFO
> [   17.944335] panel-himax-hx8394 ff960000.dsi.0: sending command 0xb9 failed: -110
> [   17.944340] panel-himax-hx8394 ff960000.dsi.0: Panel init sequence failed: -110
> 
> echo 2 > /sys/class/graphics/fb0/blank
> 
> [  431.148583] panel-himax-hx8394 ff960000.dsi.0: disable
> [  431.169259] dw-mipi-dsi-rockchip ff960000.dsi: failed to write command FIFO
> [  431.169268] panel-himax-hx8394 ff960000.dsi.0: Failed to enter sleep mode: -110
> [  431.169282] dw-mipi-dsi-rockchip ff960000.dsi: post_disable
> [  431.169316] panel-himax-hx8394 ff960000.dsi.0: unprepare
> [  431.169357] pclk_mipi_dsi0 already disabled
> 
> echo 0 > /sys/class/graphics/fb0/blank
> 
> [  432.796851] panel-himax-hx8394 ff960000.dsi.0: prepare
> [  432.981537] dw-mipi-dsi-rockchip ff960000.dsi: enable
> [  432.981568] panel-himax-hx8394 ff960000.dsi.0: enable
> [  433.002290] dw-mipi-dsi-rockchip ff960000.dsi: failed to write command FIFO
> [  433.002299] panel-himax-hx8394 ff960000.dsi.0: sending command 0xb9 failed: -110
> [  433.002312] panel-himax-hx8394 ff960000.dsi.0: Panel init sequence failed: -110
> 
> -----------------------------------------------------------------------
> 
> After:
> 
> [    1.248372] dw-mipi-dsi-rockchip ff960000.dsi: mode_set
> [    1.248704] dw-mipi-dsi-rockchip ff960000.dsi: pre_enable
> [    1.285377] panel-himax-hx8394 ff960000.dsi.0: prepare
> [    1.468392] dw-mipi-dsi-rockchip ff960000.dsi: enable
> [    1.468421] panel-himax-hx8394 ff960000.dsi.0: enable
> 
> echo 2 > /sys/class/graphics/fb0/blank
> 
> [   16.210357] panel-himax-hx8394 ff960000.dsi.0: disable
> [   16.261315] dw-mipi-dsi-rockchip ff960000.dsi: post_disable
> [   16.261339] panel-himax-hx8394 ff960000.dsi.0: unprepare
> 
> echo 0 > /sys/class/graphics/fb0/blank
> 
> [   19.161453] dw-mipi-dsi-rockchip ff960000.dsi: pre_enable
> [   19.197869] panel-himax-hx8394 ff960000.dsi.0: prepare
> [   19.382141] dw-mipi-dsi-rockchip ff960000.dsi: enable
> [   19.382158] panel-himax-hx8394 ff960000.dsi.0: enable
> 
> Signed-off-by: Ondrej Jirman <megi@xff.cz>

Nice cleanup and fix.
Have you consider if this need a Fixes: ?


> ---
>  drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 28 +++++++++++--------
>  1 file changed, 16 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> index b2efecf7d160..352c6829259a 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> @@ -265,6 +265,7 @@ struct dw_mipi_dsi {
>  	struct dw_mipi_dsi *master; /* dual-dsi master ptr */
>  	struct dw_mipi_dsi *slave; /* dual-dsi slave ptr */
>  
> +	struct drm_display_mode mode;
>  	const struct dw_mipi_dsi_plat_data *plat_data;
>  };
>  
> @@ -332,6 +333,7 @@ static int dw_mipi_dsi_host_attach(struct mipi_dsi_host *host,
>  	if (IS_ERR(bridge))
>  		return PTR_ERR(bridge);
>  
> +	bridge->pre_enable_prev_first = true;
>  	dsi->panel_bridge = bridge;
>  
>  	drm_bridge_add(&dsi->bridge);
> @@ -859,15 +861,6 @@ static void dw_mipi_dsi_bridge_post_atomic_disable(struct drm_bridge *bridge,
>  	 */
>  	dw_mipi_dsi_set_mode(dsi, 0);
>  
> -	/*
> -	 * TODO Only way found to call panel-bridge post_disable &
> -	 * panel unprepare before the dsi "final" disable...
> -	 * This needs to be fixed in the drm_bridge framework and the API
> -	 * needs to be updated to manage our own call chains...
> -	 */
> -	if (dsi->panel_bridge->funcs->post_disable)
> -		dsi->panel_bridge->funcs->post_disable(dsi->panel_bridge);
> -
>  	if (phy_ops->power_off)
>  		phy_ops->power_off(dsi->plat_data->priv_data);
>  
> @@ -942,15 +935,25 @@ static void dw_mipi_dsi_mode_set(struct dw_mipi_dsi *dsi,
>  		phy_ops->power_on(dsi->plat_data->priv_data);
>  }
>  
> +static void dw_mipi_dsi_bridge_atomic_pre_enable(struct drm_bridge *bridge,
> +						 struct drm_bridge_state *old_bridge_state)
> +{
> +	struct dw_mipi_dsi *dsi = bridge_to_dsi(bridge);
> +
> +	/* Power up the dsi ctl into a command mode */
> +	dw_mipi_dsi_mode_set(dsi, &dsi->mode);
> +	if (dsi->slave)
> +		dw_mipi_dsi_mode_set(dsi->slave, &dsi->mode);
> +}
> +
>  static void dw_mipi_dsi_bridge_mode_set(struct drm_bridge *bridge,
>  					const struct drm_display_mode *mode,
>  					const struct drm_display_mode *adjusted_mode)
>  {
>  	struct dw_mipi_dsi *dsi = bridge_to_dsi(bridge);
>  
> -	dw_mipi_dsi_mode_set(dsi, adjusted_mode);
> -	if (dsi->slave)
> -		dw_mipi_dsi_mode_set(dsi->slave, adjusted_mode);
> +	/* Store the display mode for later use in pre_enable callback */
> +	memcpy(&dsi->mode, adjusted_mode, sizeof(dsi->mode));
>  }
Use drm_mode_copy here.
With this fixed:

Reviewed-by: Sam Ravnborg <sam@ravnborg.org>