On Sat, Nov 9, 2019 at 5:02 AM Stephan Gerhold <stephan@xxxxxxxxxxx> wrote: > > On Fri, Nov 08, 2019 at 08:47:08PM -0700, Jeffrey Hugo wrote: > > On Fri, Nov 8, 2019 at 4:47 PM Stephan Gerhold <stephan@xxxxxxxxxxx> wrote: > > > > > > On Fri, Nov 08, 2019 at 03:12:28PM -0700, Jeffrey Hugo wrote: > > > > On Fri, Nov 8, 2019 at 2:29 PM Stephan Gerhold <stephan@xxxxxxxxxxx> wrote: > > > > > > > > > > At the moment, the MSM DSI driver calls drm_panel_enable() rather early > > > > > from the DSI bridge pre_enable() function. At this point, the encoder > > > > > (e.g. MDP5) is not enabled, so we have not started transmitting > > > > > video data. > > > > > > > > > > However, the drm_panel_funcs documentation states that enable() > > > > > should be called on the panel *after* video data is being transmitted: > > > > > > > > > > The .prepare() function is typically called before the display controller > > > > > starts to transmit video data. [...] After the display controller has > > > > > started transmitting video data, it's safe to call the .enable() function. > > > > > This will typically enable the backlight to make the image on screen visible. > > > > > > > > > > Calling drm_panel_enable() too early causes problems for some panels: > > > > > The TFT LCD panel used in the Samsung Galaxy Tab A 9.7 (2015) (APQ8016) > > > > > uses the MIPI_DCS_SET_DISPLAY_BRIGHTNESS command to control > > > > > backlight/brightness of the screen. The enable sequence is therefore: > > > > > > > > > > drm_panel_enable() > > > > > drm_panel_funcs.enable(): > > > > > backlight_enable() > > > > > backlight_ops.update_status(): > > > > > mipi_dsi_dcs_set_display_brightness(dsi, bl->props.brightness); > > > > > > > > > > The panel seems to silently ignore the MIPI_DCS_SET_DISPLAY_BRIGHTNESS > > > > > command if it is sent too early. This prevents setting the initial brightness, > > > > > causing the display to be enabled with minimum brightness instead. > > > > > Adding various delays in the panel initialization code does not result > > > > > in any difference. > > > > > > > > > > On the other hand, moving drm_panel_enable() to dsi_mgr_bridge_enable() > > > > > fixes the problem, indicating that the panel requires the video stream > > > > > to be active before the brightness command is accepted. > > > > > > > > > > Therefore: Move drm_panel_enable() to dsi_mgr_bridge_enable() to > > > > > delay calling it until video data is being transmitted. > > > > > > > > > > Move drm_panel_disable() to dsi_mgr_bridge_disable() for similar reasons. > > > > > (This is not strictly required for the panel affected above...) > > > > > > > > > > Tested-by: Jasper Korten <jja2000@xxxxxxxxx> > > > > > Signed-off-by: Stephan Gerhold <stephan@xxxxxxxxxxx> > > > > > --- > > > > > Since this is a core change I thought it would be better to send this > > > > > early. I believe Jasper still wants to finish some other changes before > > > > > submitting the initial device tree for the Samsung Galaxy Tab A 9.7 (2015). ;) > > > > > > > > > > I also tested it on msm8916-samsung-a5u-eur, its display is working fine > > > > > with or without this patch. > > > > > > > > Nack, please. I was curious so I threw this on the Lenovo Miix 630 > > > > laptop. I don't get a display back with this patch. I'll try to > > > > figure out why, but currently I can't get into the machine. > > > > > > Thanks for testing the patch! Let's try to figure that out... > > > > > > I'm a bit confused, but this might be because I'm not very familiar with > > > the MSM8998 laptops. It does not seem to have display in mainline yet, > > > so do you have a link to all the patches you are using at the moment? > > > > The mdp5 support is there. Some of the dependencies have dragged out. > > I'd have to make sense of my development tree as to what is relevant. > > A dump of all the patches (whether still relevant or not) would be > helpful too. Actually I was mostly looking for the device tree part to > see which components are involved. DSI0 to "ti,sn65dsi86" (bridge) to "sharp,ld-d5116z01b" (panel). > > > > > > > Judging from the patches I was able to find, the Lenovo Miix 630 is > > > using a DSI to eDP bridge. > > > Isn't the panel managed by the bridge driver in that case? > > > > It uses the TI SN65 bridge. > > > > It is covered by the ti-sn65dsi86 driver I assume? Yes > > > > > > > struct msm_dsi contains: > > > /* > > > * panel/external_bridge connected to dsi bridge output, only one of the > > > * two can be valid at a time > > > */ > > > struct drm_panel *panel; > > > struct drm_bridge *external_bridge; > > > > > > So if you have "external_bridge" set in your case, "panel" should be NULL. > > > I have only moved code that uses msm_dsi->panel, so my patch really > > > shouldn't make any difference for you. > > > > > > Am I confusing something here? > > > > I don't think panel is null in my case. I need to trace a few things > > through to be sure. > > > > ti-sn65dsi86.c contains: > > static void ti_sn_bridge_enable(struct drm_bridge *bridge) > { > /* ... */ > drm_panel_enable(pdata->panel); > } > > static void ti_sn_bridge_pre_enable(struct drm_bridge *bridge) > { > /* ... */ > drm_panel_prepare(pdata->panel); > } > > So it does indeed manage the panel for you. If msm_dsi->panel is not > NULL for you it would mean that your panel is managed by two drivers > at the same time. > > (Also note how it calls drm_panel_enable() in enable() instead of > pre_enable(). This is exactly the change my patch does for the case > when the panel is managed by the MSM driver...) > > > Taking a quick look at the datasheet for the bridge, I suspect that > > operations are occurring in the enable() phase of the bridge, that > > need to occur before video data is transmitted. Based on your > > analysis in the commit message, I suspect these operations need to be > > moved to pre_enable(). > > > > I'm still confused how my patch makes any difference for you. > The enable sequence should be exactly the same as before. > > > I'm hoping to gather more data this weekend, which will hopefully > > identify what we need to do to move this forward without causing > > regressions. > > Looking forward to it, thanks! Panel was infact NULL for me, and the DSI panel operations are not translating into direct bridge calls. I re-applied your change, and I'm not reproing the original failure. I tried a couple of times to be sure. I have no idea what happened during the initial testing to break things. Therefore, I remove my nack. Tested-by: Jeffrey Hugo <jeffrey.l.hugo@xxxxxxxxx> Reviewed-by: Jeffrey Hugo <jeffrey.l.hugo@xxxxxxxxx>