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From: Bjorn Andersson <bjorn.andersson@linaro.org>
To: Douglas Anderson <dianders@chromium.org>
Cc: Andrzej Hajda <a.hajda@samsung.com>,
	Neil Armstrong <narmstrong@baylibre.com>,
	Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
	Jonas Karlman <jonas@kwiboo.se>,
	Jernej Skrabec <jernej.skrabec@siol.net>,
	Sam Ravnborg <sam@ravnborg.org>, Wolfram Sang <wsa@kernel.org>,
	Stephen Boyd <swboyd@chromium.org>,
	robdclark@chromium.org,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>,
	Steev Klimaszewski <steev@kali.org>,
	linux-arm-msm@vger.kernel.org, Linus W <linus.walleij@linaro.org>,
	Daniel Vetter <daniel@ffwll.ch>, David Airlie <airlied@linux.ie>,
	Robert Foss <robert.foss@linaro.org>,
	dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 25/27] drm/bridge: ti-sn65dsi86: Don't read EDID blob over DDC
Date: Fri, 23 Apr 2021 11:13:35 -0500
Message-ID: <YILyL+V4tgNX8mck@builder.lan> (raw)
In-Reply-To: <20210416153909.v4.25.I9330684c25f65bb318eff57f0616500f83eac3cc@changeid>

On Fri 16 Apr 17:39 CDT 2021, Douglas Anderson wrote:

> This is really just a revert of commit 58074b08c04a ("drm/bridge:
> ti-sn65dsi86: Read EDID blob over DDC"), resolving conflicts.
> 
> The old code failed to read the EDID properly in a very important
> case: before the bridge's pre_enable() was called. The way things need
> to work:
> 1. Read the EDID.
> 2. Based on the EDID, decide on video settings and pixel clock.
> 3. Enable the bridge w/ the desired settings.
> 
> The way things were working:
> 1. Try to read the EDID but fail; fall back to hardcoded values.
> 2. Based on hardcoded values, decide on video settings and pixel clock.
> 3. Enable the bridge w/ the desired settings.
> 4. Try again to read the EDID, it works now!
> 5. Realize that the hardcoded settings weren't quite right.
> 6. Disable / reenable the bridge w/ the right settings.
> 
> The reasons for the failures were twofold:
> a) Since we never ran the bridge chip's pre-enable then we never set
>    the bit to ignore HPD. This meant the bridge chip didn't even _try_
>    to go out on the bus and communicate with the panel.
> b) Even if we fixed things to ignore HPD, the EDID still wouldn't read
>    if the panel wasn't on.
> 
> Instead of reverting the code, we could fix it to set the HPD bit and
> also power on the panel. However, it also works nicely to just let the
> panel code read the EDID. Now that we've split the driver up we can
> expose the DDC AUX channel bus to the panel node. The panel can take
> charge of reading the EDID.
> 
> NOTE: in order for things to work, anyone that needs to read the EDID
> will need to add something that looks like this to their panel in the
> dts:
>   ddc-i2c-bus = <&sn65dsi86_bridge>;
> 
> Presumably it's OK to land this without waiting for users to add the
> dts property since the EDID reading was a bit broken anyway, was
> "recently" added, and we know we must have the fallback mode to use
> (since the EDID reading was a bit broken).
> 
> Suggested-by: Andrzej Hajda <a.hajda@samsung.com>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>

Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>

Regards,
Bjorn

> ---
> 
> (no changes since v1)
> 
>  drivers/gpu/drm/bridge/ti-sn65dsi86.c | 22 ----------------------
>  1 file changed, 22 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> index 8253098bcdbf..62904dfdee0a 100644
> --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> @@ -125,7 +125,6 @@
>   * @connector:    Our connector.
>   * @host_node:    Remote DSI node.
>   * @dsi:          Our MIPI DSI source.
> - * @edid:         Detected EDID of eDP panel.
>   * @refclk:       Our reference clock.
>   * @panel:        Our panel.
>   * @enable_gpio:  The GPIO we toggle to enable the bridge.
> @@ -156,7 +155,6 @@ struct ti_sn65dsi86 {
>  	struct drm_dp_aux		aux;
>  	struct drm_bridge		bridge;
>  	struct drm_connector		connector;
> -	struct edid			*edid;
>  	struct device_node		*host_node;
>  	struct mipi_dsi_device		*dsi;
>  	struct clk			*refclk;
> @@ -404,24 +402,6 @@ connector_to_ti_sn65dsi86(struct drm_connector *connector)
>  static int ti_sn_bridge_connector_get_modes(struct drm_connector *connector)
>  {
>  	struct ti_sn65dsi86 *pdata = connector_to_ti_sn65dsi86(connector);
> -	struct edid *edid = pdata->edid;
> -	int num, ret;
> -
> -	if (!edid) {
> -		pm_runtime_get_sync(pdata->dev);
> -		edid = pdata->edid = drm_get_edid(connector, &pdata->aux.ddc);
> -		pm_runtime_put_autosuspend(pdata->dev);
> -	}
> -
> -	if (edid && drm_edid_is_valid(edid)) {
> -		ret = drm_connector_update_edid_property(connector, edid);
> -		if (!ret) {
> -			num = drm_add_edid_modes(connector, edid);
> -			if (num)
> -				return num;
> -		}
> -	}
> -
>  	return drm_panel_get_modes(pdata->panel, connector);
>  }
>  
> @@ -1330,8 +1310,6 @@ static void ti_sn_bridge_remove(struct auxiliary_device *adev)
>  		mipi_dsi_device_unregister(pdata->dsi);
>  	}
>  
> -	kfree(pdata->edid);
> -
>  	drm_bridge_remove(&pdata->bridge);
>  
>  	of_node_put(pdata->host_node);
> -- 
> 2.31.1.368.gbe11c130af-goog
> 

  reply index

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-16 22:39 [PATCH v4 00/27] drm: Fix EDID reading on ti-sn65dsi86; solve some chicken-and-egg problems Douglas Anderson
2021-04-16 22:39 ` [PATCH v4 01/27] drm/bridge: Fix the stop condition of drm_bridge_chain_pre_enable() Douglas Anderson
2021-04-16 22:39 ` [PATCH v4 02/27] drm/bridge: ti-sn65dsi86: Simplify refclk handling Douglas Anderson
2021-04-16 22:39 ` [PATCH v4 03/27] drm/bridge: ti-sn65dsi86: Remove incorrectly tagged kerneldoc comment Douglas Anderson
2021-04-16 22:39 ` [PATCH v4 04/27] drm/bridge: ti-sn65dsi86: Reorder remove() Douglas Anderson
2021-04-16 22:39 ` [PATCH v4 05/27] drm/bridge: ti-sn65dsi86: Move drm_panel_unprepare() to post_disable() Douglas Anderson
2021-04-16 22:39 ` [PATCH v4 06/27] drm/bridge: ti-sn65dsi86: Get rid of the useless detect() function Douglas Anderson
2021-04-16 22:39 ` [PATCH v4 07/27] drm/panel: panel-simple: Use runtime pm to avoid excessive unprepare / prepare Douglas Anderson
2021-04-16 22:39 ` [PATCH v4 08/27] drm/bridge: ti-sn65dsi86: Rename the main driver data structure Douglas Anderson
2021-04-23 14:28   ` Bjorn Andersson
2021-04-16 22:39 ` [PATCH v4 09/27] drm/bridge: ti-sn65dsi86: More renames in prep for sub-devices Douglas Anderson
2021-04-23 14:30   ` Bjorn Andersson
2021-04-16 22:39 ` [PATCH v4 10/27] drm/bridge: ti-sn65dsi86: Clean debugfs code Douglas Anderson
2021-04-23 14:35   ` Bjorn Andersson
2021-04-16 22:39 ` [PATCH v4 11/27] drm/bridge: ti-sn65dsi86: Add local var for "dev" to simplify probe Douglas Anderson
2021-04-23 14:38   ` Bjorn Andersson
2021-04-16 22:39 ` [PATCH v4 12/27] drm/bridge: ti-sn65dsi86: Cleanup managing of drvdata Douglas Anderson
2021-04-23 14:38   ` Bjorn Andersson
2021-04-16 22:39 ` [PATCH v4 13/27] drm/bridge: ti-sn65dsi86: Use devm to do our runtime_disable Douglas Anderson
2021-04-23 14:39   ` Bjorn Andersson
2021-04-16 22:39 ` [PATCH v4 14/27] drm/bridge: ti-sn65dsi86: Move all the chip-related init to the start Douglas Anderson
2021-04-23 14:41   ` Bjorn Andersson
2021-04-16 22:39 ` [PATCH v4 15/27] drm/bridge: ti-sn65dsi86: Break GPIO and MIPI-to-eDP bridge into sub-drivers Douglas Anderson
2021-04-23 14:49   ` Bjorn Andersson
2021-04-16 22:39 ` [PATCH v4 16/27] drm/panel: panel-simple: Get rid of hacky HPD chicken-and-egg code Douglas Anderson
2021-04-23 14:50   ` Bjorn Andersson
2021-04-16 22:39 ` [PATCH v4 17/27] drm/bridge: ti-sn65dsi86: Use pm_runtime autosuspend Douglas Anderson
2021-04-23 14:51   ` Bjorn Andersson
2021-04-16 22:39 ` [PATCH v4 18/27] drm/bridge: ti-sn65dsi86: Code motion of refclk management functions Douglas Anderson
2021-04-23 14:51   ` Bjorn Andersson
2021-04-16 22:39 ` [PATCH v4 19/27] drm/bridge: ti-sn65dsi86: If refclk, DP AUX can happen w/out pre-enable Douglas Anderson
2021-04-23 14:56   ` Bjorn Andersson
2021-04-16 22:39 ` [PATCH v4 20/27] drm/bridge: ti-sn65dsi86: Promote the AUX channel to its own sub-dev Douglas Anderson
2021-04-23 14:59   ` Bjorn Andersson
2021-04-16 22:39 ` [PATCH v4 21/27] i2c: i2c-core-of: Fix corner case of finding adapter by node Douglas Anderson
2021-04-23 15:12   ` Bjorn Andersson
2021-04-16 22:39 ` [PATCH v4 22/27] drm/panel: panel-simple: Remove extra call: drm_connector_update_edid_property() Douglas Anderson
2021-04-23 15:15   ` Bjorn Andersson
2021-04-16 22:39 ` [PATCH v4 23/27] drm/panel: panel-simple: Power the panel when reading the EDID Douglas Anderson
2021-04-23 15:16   ` Bjorn Andersson
2021-04-16 22:39 ` [PATCH v4 24/27] drm/panel: panel-simple: Cache the EDID as long as we retain power Douglas Anderson
2021-04-23 16:12   ` Bjorn Andersson
2021-04-23 16:30     ` Doug Anderson
2021-04-16 22:39 ` [PATCH v4 25/27] drm/bridge: ti-sn65dsi86: Don't read EDID blob over DDC Douglas Anderson
2021-04-23 16:13   ` Bjorn Andersson [this message]
2021-04-16 22:39 ` [PATCH v4 26/27] arm64: dts: qcom: Link the panel to the bridge's DDC bus Douglas Anderson
2021-04-23 16:16   ` Bjorn Andersson
2021-04-16 22:39 ` [PATCH v4 27/27] drm/panel: panel-simple: Prepare/unprepare are refcounted, not forced Douglas Anderson
2021-04-23 16:16   ` Bjorn Andersson
2021-04-23 16:46   ` Doug Anderson
2021-04-20 16:42 ` [PATCH v4 00/27] drm: Fix EDID reading on ti-sn65dsi86; solve some chicken-and-egg problems Doug Anderson

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