On 12/14/2016 01:01 AM, Stefan Agner wrote: > On 2016-12-08 15:38, Marek Vasut wrote: >> On 12/08/2016 09:46 PM, Stefan Agner wrote: >>> On 2016-12-07 18:37, Marek Vasut wrote: >>>> On 12/08/2016 02:26 AM, Stefan Agner wrote: >>>>> On 2016-12-07 16:59, Stefan Agner wrote: >>>>>> On 2016-12-07 16:49, Marek Vasut wrote: >>>>>>> On 12/08/2016 01:27 AM, Stefan Agner wrote: >>>>>>>> The DRM subsystem specifies the pixel clock polarity from a >>>>>>>> controllers perspective: DRM_BUS_FLAG_PIXDATA_NEGEDGE means >>>>>>>> the controller drives the data on pixel clocks falling edge. >>>>>>>> That is the controllers DOTCLK_POL=0 (Default is data launched >>>>>>>> at negative edge). >>>>>>>> >>>>>>>> Also change the data enable logic to be high active by default >>>>>>>> and only change if explicitly requested via bus_flags. With >>>>>>>> that defaults are: >>>>>>>> - Data enable: high active >>>>>>>> - Pixel clock polarity: controller drives data on negative edge >>>>>>>> >>>>>>>> Signed-off-by: Stefan Agner <stefan@xxxxxxxx> >>>>>>>> --- >>>>>>>> Hi Marek, >>>>>>> >>>>>>> Hi, that was quick, thanks for checking this. >>>>>> >>>>>> Yeah, I couldn't wait seeing it flying :-) >>>>>> >>>>>>> >>>>>>>> I discovered this while testing on a i.MX 7 eLCDIF IP. Particularly the >>>>>>>> non-standard DE polarity was causing issues. I was using a EDT display >>>>>>>> which is part of simple panel driver since a while now and does not >>>>>>>> specify any bus_flags currently... Of course I could (and probably should) >>>>>>>> add the proper bus_flags there too, but there are several displays >>>>>>>> which do not specify any polarity and likely rely on sensible driver >>>>>>>> standards (which is afact high active for the DE signal). >>>>>>> >>>>>>> I actually use a panel which requires correct settings of the flags, see >>>>>>> e0932f9d7ba9a16f99a84943b720f109de8e3e06 in mainline , so this patch >>>>>>> would break things for me. So I wonder whether you should fix the panel >>>>>>> driver or whether the mxsfb should be fixed ? >>>>>> >>>>>> If you ask me, mxsfb. >>>>>> >>>>>> Ok, there are actually two things, one is a bug, one is a default >>>>>> change. >>>>>> >>>>>> The bug: Pixel clock polarity is clearly defined to be controller >>>>>> centric (see comments around DRM_BUS_FLAG_PIXDATA_*EDGE in >>>>>> include/drm/drm_connector.h). The driver does it wrong currently. >>>>>> >>>>>> This might affect your display, and if it does, it is actually wrong >>>>>> also in your display... However, since it is a bug, I think it is not >>>>>> really a debate, it should be fixed... >>>>> >>>>> FWIW, it seems that Ortustech com43h4m85ulc samples on falling edge, so >>>>> DRM_BUS_FLAG_PIXDATA_POSEDGE seems right. And it means that DOTCLK_POL >>>>> should be 1 (inverted), so with this patch the polarity should actually >>>>> be correct for that panel. >>>> >>>> Well, if I apply this patch, my image is shifted by 1 px to the left and >>>> there is a 1px white bar on the right side, so I think I have some >>>> polarity problem now ? >>> >>> Ok, lets create facts here: >>> 1. SoloX Refrence Manual, Figure 37-13. shows DOTCLK_POL=0, and it shows >>> that the controller drives signals on falling edge of the pixel clock. >>> The i.MX 7 has the same figure. >>> 2. Just to verify, I hooked up an oscilloscope on my i.MX 7: It shows >>> that with DOTCLK_POL=0 the controller drives on falling edge: >>> http://imgur.com/a/2f2Xt >>> >>> So my measurements verify what is in the i.MX data sheets. >> >> Good >> >>> The current code sets the bit when negative edge (falling edge) is >>> requested, which is wrong: >>> #define VDCTRL0_DOTCLK_ACT_FALLING (1 << 25) >>> ... >>> if (bus_flags & DRM_BUS_FLAG_PIXDATA_NEGEDGE) >>> vdctrl0 |= VDCTRL0_DOTCLK_ACT_FALLING; >>> >>> Not sure what is going on with your display, maybe the datasheet is just >>> wrong (it requires DRM_BUS_FLAG_PIXDATA_NEGEDGE in fact) or it is some >>> other artifact. >> >> This is probably where the problem crept in [1], droping PIXDATA_POSEDGE >> actually makes this patch work for me. CCing Philipp. >> >> [1] https://patchwork.kernel.org/patch/9301517/ > > I looked at a old data sheet of that display and it seemed that > PIXDATA_POSEDGE is the right thing. Panelook.cn lists newer data sheets, > but I couldn't find them on the open internet, do you have access to a > newer one? Which "version" do you have ? Probably not though. > http://www.panelook.cn/COM43H4M85ULC_ORTUSTECH_4.3_LCM_overview_17296.html > > I guess in the end it doesn't matter: Given that it is verified that the > controllers data sheet is right, I vote for merging that patch and fix > the displays polarity... Merging which patch ? -- Best regards, Marek Vasut _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
