On Thu, 13 Jul 2023 at 23:58, Marek Vasut <marex@xxxxxxx> wrote: > > On 7/13/23 20:09, Abhinav Kumar wrote: > > > > > > On 7/12/2023 10:41 AM, Marek Vasut wrote: > >> On 7/9/23 03:03, Abhinav Kumar wrote: > >>> > >>> > >>> On 7/7/2023 1:47 AM, Neil Armstrong wrote: > >>>> On 07/07/2023 09:18, Neil Armstrong wrote: > >>>>> Hi, > >>>>> > >>>>> On 06/07/2023 11:20, Amit Pundir wrote: > >>>>>> On Wed, 5 Jul 2023 at 11:09, Dmitry Baryshkov > >>>>>> <dmitry.baryshkov@xxxxxxxxxx> wrote: > >>>>>>> > >>>>>>> [Adding freedreno@ to cc list] > >>>>>>> > >>>>>>> On Wed, 5 Jul 2023 at 08:31, Jagan Teki > >>>>>>> <jagan@xxxxxxxxxxxxxxxxxxxx> wrote: > >>>>>>>> > >>>>>>>> Hi Amit, > >>>>>>>> > >>>>>>>> On Wed, Jul 5, 2023 at 10:15 AM Amit Pundir > >>>>>>>> <amit.pundir@xxxxxxxxxx> wrote: > >>>>>>>>> > >>>>>>>>> Hi Marek, > >>>>>>>>> > >>>>>>>>> On Wed, 5 Jul 2023 at 01:48, Marek Vasut <marex@xxxxxxx> wrote: > >>>>>>>>>> > >>>>>>>>>> Do not generate the HS front and back porch gaps, the HSA gap and > >>>>>>>>>> EOT packet, as these packets are not required. This makes the > >>>>>>>>>> bridge > >>>>>>>>>> work with Samsung DSIM on i.MX8MM and i.MX8MP. > >>>>>>>>> > >>>>>>>>> This patch broke display on Dragonboard 845c (SDM845) devboard > >>>>>>>>> running > >>>>>>>>> AOSP. This is what I see > >>>>>>>>> https://people.linaro.org/~amit.pundir/db845c-userdebug/v6.5-broken-display/PXL_20230704_150156326.jpg. > >>>>>>>>> Reverting this patch fixes this regression for me. > >>>>>>>> > >>>>>>>> Might be msm dsi host require proper handling on these updated > >>>>>>>> mode_flags? did they? > >>>>>>> > >>>>>>> The msm DSI host supports those flags. Also, I'd like to point out > >>>>>>> that the patch didn't change the rest of the driver code. So even if > >>>>>>> drm/msm ignored some of the flags, it should not have caused the > >>>>>>> issue. Most likely the issue is on the lt9611 side. I's suspect that > >>>>>>> additional programming is required to make it work with these flags. > >>>>>> > >>>>>> I spent some time today on smoke testing these flags (individually > >>>>>> and > >>>>>> in limited combination) on DB845c, to narrow down this breakage to > >>>>>> one > >>>>>> or more flag(s) triggering it. Here are my observations in limited > >>>>>> testing done so far. > >>>>>> > >>>>>> There is no regression with MIPI_DSI_MODE_NO_EOT_PACKET when enabled > >>>>>> alone and system boots to UI as usual. > >>>>>> > >>>>>> MIPI_DSI_MODE_VIDEO_NO_HFP always trigger the broken display as in > >>>>>> the > >>>>>> screenshot[1] shared earlier as well. > >>>>>> > >>>>>> Adding either of MIPI_DSI_MODE_VIDEO_NO_HSA and > >>>>>> MIPI_DSI_MODE_VIDEO_NO_HBP always result in no display, unless paired > >>>>>> with MIPI_DSI_MODE_VIDEO_NO_HFP and in that case we get the broken > >>>>>> display as reported. > >>>>>> > >>>>>> In short other than MIPI_DSI_MODE_NO_EOT_PACKET flag, all other flags > >>>>>> added in this commit break the display on DB845c one way or another. > >>>>> > >>>>> I think the investigation would be to understand why samsung-dsim > >>>>> requires > >>>>> such flags and/or what are the difference in behavior between MSM > >>>>> DSI and samsung DSIM > >>>>> for those flags ? > >>>>> > >>>>> If someone has access to the lt9611 datasheet, so it requires > >>>>> HSA/HFP/HBP to be > >>>>> skipped ? and does MSM DSI and samsung DSIM skip them in the same > >>>>> way ? > >>>> > >>>> I think there's a mismatch, where on one side this flags sets the > >>>> link in LP-11 while > >>>> in HSA/HFP/HPB while on the other it completely removes those > >>>> blanking packets. > >>>> > >>>> The name MIPI_DSI_MODE_VIDEO_NO_HBP suggests removal of HPB, not > >>>> LP-11 while HPB. > >>>> the registers used in both controllers are different: > >>>> - samsung-dsim: DSIM_HBP_DISABLE_MODE > >>>> - msm dsi: DSI_VID_CFG0_HBP_POWER_STOP > >>>> > >>>> The first one suggest removing the packet, while the second one > >>>> suggests powering > >>>> off the line while in the blanking packet period. > >>>> > >>>> @Abhinav, can you comment on that ? > >>>> > >>> > >>> I dont get what it means by completely removes blanking packets in DSIM. > >> > >> MIPI_DSI_MODE_VIDEO_NO_HFP means the HBP period is just skipped by DSIM. > >> > >> Maybe there is a need for new set of flags which differentiate between > >> HBP skipped (i.e. NO HBP) and HBP LP11 ? > >> > > > > No, the section of the MIPI DSI spec I posted below clearly states there > > are two options: > > > > 1) send blanking packets during those periods > > 2) transition to LP11 during those periods > > > > There is no 3rd option in the spec of not doing both like what you are > > suggesting. So DSIM should also be only transitioning to LP11 during > > those periods if its not sending the blanking packets with those flags set. > > > > So, there is no need for any new set of flags to differentiate. > > > > The flags and their interpretation is correct in MSM driver. I cannot > > comment on what exactly DSIM does with those flags. > > How do you explain the comment in include/drm/drm_mipi_dsi.h: > > 128 /* disable hback-porch area */ > 129 #define MIPI_DSI_MODE_VIDEO_NO_HBP BIT(6) > > Esp. the "disable" part. That to me reads as "don't send HBP packet". > > Where do you see that quote above in the DSI spec (which chapter and > which version do you read) ? > > >>> It should be replacing those periods with LP11 too. > >>> > >>> The traffic mode being used on this bridge is > >>> MIPI_DSI_MODE_VIDEO_SYNC_PULSE which is "Non-Burst Mode with Sync > >>> Pulses". > >>> > >>> As per this traffic mode in the DSI spec, > >>> > >>> "Normally, periods shown as HSA (Horizontal Sync Active), HBP > >>> (Horizontal Back Porch) and HFP (Horizontal Front Porch) are filled > >>> by Blanking Packets, with lengths (including packet overhead) > >>> calculated to match the period specified by the peripheral’s data > >>> sheet. Alternatively, if there is sufficient time to transition from > >>> HS to LP mode and back again, a timed interval in LP mode may > >>> substitute for a Blanking Packet, thus saving power. During HSA, HBP > >>> and HFP periods, the bus should stay in the LP-11 state." > >>> > >>> So we can either send the blanking packets or transition to LP state > >>> and those 3 flags are controlling exactly that during those periods > >>> for MSM driver. > >>> > >>> If you stop sending the blanking packets, you need to replace that > >>> gap with LP. > >> > >> I don't think that's what MIPI_DSI_MODE_VIDEO_NO_HBP means, the way I > >> understand MIPI_DSI_MODE_VIDEO_NO_HBP is that it skips the HBP > >> completely. So if you want HBP, then do not set > >> MIPI_DSI_MODE_VIDEO_NO_HBP . And if you want LP11 during HBP, that is > >> I think up to the controller (or maybe another new flag?). > >> > > > > No, there is no need of another new flag. There are only two options as > > per the spec. > > > > In fact, as per my checking with more folks, requiring LP11 during those > > periods is something very rare. > > > > Because usually horizontal period is usually a very short period, most > > of the time we do not use the LP11 option and send the blanking packets > > instead. > > > > So its something very unusual for DSIM. > > > > That being said, I still think my previous question is important. > > > > 1) What is the difference between the resolution you are trying Vs what > > Amit is trying? > > > > 2) Are you both using just standard HDMI monitors? > > What is a "standard HDMI monitor" ? > I use DELL U2713HM . I see this breakage on portable HDMI monitors Viewsonic TD1655 [1] and Cocopar Z173FH7F [2], both running at 1920x1080 resolution. Regards, Amit Pundir [1] https://www.amazon.in/ViewSonic-TD1655-Portable-Touchscreen-Frameless/dp/B08778F756 [2] https://www.amazon.com/Portable-Monitor-FreeSync-Speaker-Nintendo/dp/B07ZLXCVPN > > [...]
