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[46.138.17.53]) by smtp.googlemail.com with ESMTPSA id k21sm1798140lji.107.2021.07.18.13.59.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 18 Jul 2021 13:59:52 -0700 (PDT) Subject: Re: [PATCH v18 0/2] Add memory bandwidth management to NVIDIA Tegra DRM driver From: Dmitry Osipenko To: Thierry Reding References: <20210601042108.1942-1-digetx@gmail.com> <8accfe1e-fc48-21ca-f7c6-bd2d60162e6d@gmail.com> <50912a57-aa43-58b0-02d2-6928578d6286@gmail.com> Message-ID: <0e81b357-d631-fcc1-bc54-946825093642@gmail.com> Date: Sun, 18 Jul 2021 23:59:51 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-pm@vger.kernel.org, Nicolas Chauvet , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Jonathan Hunter , Matt Merhar , Peter Geis , linux-tegra@vger.kernel.org, =?UTF-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" 21.06.2021 14:43, Dmitry Osipenko пишет: > 21.06.2021 14:01, Thierry Reding пишет: >> On Mon, Jun 21, 2021 at 07:19:15AM +0300, Dmitry Osipenko wrote: >>> 07.06.2021 01:40, Dmitry Osipenko пишет: >>>> 01.06.2021 07:21, Dmitry Osipenko пишет: >>>>> This series adds memory bandwidth management to the NVIDIA Tegra DRM driver, >>>>> which is done using interconnect framework. It fixes display corruption that >>>>> happens due to insufficient memory bandwidth. >>>>> >>>>> Changelog: >>>>> >>>>> v18: - Moved total peak bandwidth from CRTC state to plane state and removed >>>>> dummy plane bandwidth state initialization from T186+ plane hub. This >>>>> was suggested by Thierry Reding to v17. >>>>> >>>>> - I haven't done anything about the cursor's plane bandwidth which >>>>> doesn't contribute to overlapping bandwidths for a small sized >>>>> window because it works okay as-is. >>>> >>>> Thierry, will you take these patches for 5.14? >>>> >>> >>> The display controller does _NOT_WORK_ properly without bandwidth >>> management. >> >> That's surprising. So either it has never worked before (which I think >> I'd know) or something has caused this regression recently. In the >> latter case we need to identify what that was and revert (or fix) it. > > The problem is caused by the support of dynamic memory frequency scaling > which does a good job at keeping memory in a low power state during idle > time. So display controller may not get enough bandwidth at the start of > scanout if it won't request BW beforehand. This problem existed for many > years on T124 and now T20/30 are also affected. The DC of T20 is the > least tolerant to memory bandwidth troubles. > > This problem is not critical, but it hurts user experience since high > resolution modes may not work at all and display output may become > distorted, requiring a DC reset. > >>> Can we get this patch into 5.14? What is the problem? >> >> There was not enough time to review and test this, so I didn't feel >> comfortable picking it up so close to the -rc6 cut-off. I plan to pick >> this up early in the v5.14 release cycle and target v5.15. > > Thank you for the explanation! It's not uncommon to forget about > patches, so the silence worries me. I hoped that both the dynamic freq > scaling and display BW support would be merged around the same time, but > apparently we got a disconnect here. > Reminder ping :)