Messages in this thread |  | | Subject | Re: [PATCH v3 6/9] drm/bridge: ti-sn65dsi86: Use 18-bit DP if we can | From | Steev Klimaszewski <> | Date | Thu, 9 Jul 2020 22:17:14 -0500 |
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On 7/9/20 10:12 PM, Steev Klimaszewski wrote: > > On 7/9/20 9:14 PM, Doug Anderson wrote: >> Hi, >> >> On Thu, Jul 9, 2020 at 6:38 PM Doug Anderson <dianders@chromium.org> >> wrote: >>> Hi, >>> >>> On Thu, Jul 9, 2020 at 6:19 PM Steev Klimaszewski <steev@gentoo.org> >>> wrote: >>>> Hi Doug, >>>> >>>> I've been testing 5.8 and linux-next on the Lenovo Yoga C630, and >>>> with this patch applied, there is really bad banding on the display. >>>> >>>> I'm really bad at explaining it, but you can see the differences in >>>> the following: >>>> >>>> 24bit (pre-5.8) - https://dev.gentoo.org/~steev/files/image0.jpg >>>> >>>> 18bit (5.8/linux-next) - >>>> https://dev.gentoo.org/~steev/files/image1.jpg >>> Presumably this means that your panel is defined improperly? If the >>> panel reports that it's a 6 bits per pixel panel but it's actually an >>> 8 bits per pixel panel then you'll run into this problem. >>> >>> I would have to assume you have a bunch of out of tree patches to >>> support your hardware since I don't see any device trees in linuxnext >>> (other than cheza) that use this bridge chip. Otherwise I could try >>> to check and confirm that was the problem. >> Ah, interesting. Maybe you have the panel: >> >> boe,nv133fhm-n61 >> >> As far as I can tell from the datasheet (I have the similar >> boe,nv133fhm-n62) this is a 6bpp panel. ...but if you feed it 8bpp >> the banding goes away! Maybe the panel itself knows how to dither??? >> ...or maybe the datasheet / edid are wrong and this is actually an >> 8bpp panel. Seems unlikely... >> >> In any case, one fix is to pick >> <https://lore.kernel.org/dri-devel/1593087419-903-1-git-send-email-kalyan_t@codeaurora.org/>, >> >> though right now that patch is only enabled for sc7180. Maybe you >> could figure out how to apply it to your hardware? >> >> ...another fix would be to pretend that your panel is 8bpp even though >> it's actually 6bpp. Ironically if anyone ever tried to configure BPP >> from the EDID they'd go back to 6bpp. You can read the EDID of your >> panel with this: >> >> bus=$(i2cdetect -l | grep sn65 | sed 's/i2c-\([0-9]*\).*$/\1/') >> i2cdump ${bus} 0x50 i >> >> When I do that and then decode it on the "boe,nv133fhm-n62" panel, I >> find: >> >> 6 bits per primary color channel >> >> -Doug > > > Hi Doug, > > Decoding it does show be to boe,nv133fhm-n61 - and yeah it does say > it's 6-bit according to panelook's specs for it. > > > I'll take a look at the patch and see what I can come up with... at > the moment, I'm forcing it to be 8bit and that does "work fine" but > I'd like it to be fixed properly instead of my hack. > > Thanks for your time and work! > > -- Steev > For what it's worth - the 5.8 that I'm testing is at https://github.com/steev/linux/commits/c630-5.8-rc4-inline-encryption
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