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[82.66.176.246]) by smtp.gmail.com with ESMTPSA id k6-20020adfd846000000b00314315071bbsm3699097wrl.38.2023.07.07.00.18.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 07 Jul 2023 00:18:11 -0700 (PDT) Message-ID: Date: Fri, 7 Jul 2023 09:18:09 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 From: Neil Armstrong Reply-To: neil.armstrong@linaro.org Subject: Re: [PATCH 2/2] drm/bridge: lt9611: Do not generate HFP/HBP/HSA and EOT packet Content-Language: en-US To: Amit Pundir , Dmitry Baryshkov Cc: Jagan Teki , Marek Vasut , dri-devel@lists.freedesktop.org, Robert Foss , Andrzej Hajda , Jonas Karlman , Jernej Skrabec , Michael Walle , Laurent Pinchart , linux-arm-msm , Linux regressions mailing list , freedreno References: <20230403221233.500485-1-marex@denx.de> <20230403221233.500485-2-marex@denx.de> Organization: Linaro Developer Services In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org Hi, On 06/07/2023 11:20, Amit Pundir wrote: > On Wed, 5 Jul 2023 at 11:09, Dmitry Baryshkov > wrote: >> >> [Adding freedreno@ to cc list] >> >> On Wed, 5 Jul 2023 at 08:31, Jagan Teki wrote: >>> >>> Hi Amit, >>> >>> On Wed, Jul 5, 2023 at 10:15 AM Amit Pundir wrote: >>>> >>>> Hi Marek, >>>> >>>> On Wed, 5 Jul 2023 at 01:48, Marek Vasut 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 ? Neil > > Regards, > Amit Pundir > [1] https://people.linaro.org/~amit.pundir/db845c-userdebug/v6.5-broken-display/PXL_20230704_150156326.jpg > >> >> -- >> With best wishes >> Dmitry