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[104.57.184.186]) by smtp.gmail.com with ESMTPSA id w2sm1272005oov.23.2021.04.23.09.13.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 23 Apr 2021 09:13:37 -0700 (PDT) Date: Fri, 23 Apr 2021 11:13:35 -0500 From: Bjorn Andersson To: Douglas Anderson Cc: Andrzej Hajda , Neil Armstrong , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Sam Ravnborg , Wolfram Sang , Stephen Boyd , robdclark@chromium.org, Maarten Lankhorst , Stanislav Lisovskiy , Steev Klimaszewski , linux-arm-msm@vger.kernel.org, Linus W , Daniel Vetter , David Airlie , Robert Foss , 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 Message-ID: References: <20210416223950.3586967-1-dianders@chromium.org> <20210416153909.v4.25.I9330684c25f65bb318eff57f0616500f83eac3cc@changeid> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210416153909.v4.25.I9330684c25f65bb318eff57f0616500f83eac3cc@changeid> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > Signed-off-by: Douglas Anderson Reviewed-by: Bjorn Andersson 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 >