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[88.156.142.67]) by smtp.gmail.com with ESMTPSA id c6-20020a056512324600b004ab52b0bcf9sm1558968lfr.207.2022.12.12.01.23.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 12 Dec 2022 01:23:27 -0800 (PST) Message-ID: <5f61cc70-9501-ee4e-010f-5188f87e3ef1@linaro.org> Date: Mon, 12 Dec 2022 10:23:26 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.1 Subject: Re: [PATCH 1/2] dt-bindings: drm/bridge: ti-sn65dsi83: Add enable delay property Content-Language: en-US To: Frieder Schrempf , Marek Vasut , Alexander Stein Cc: Krzysztof Kozlowski , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , David Airlie , Daniel Vetter , Rob Herring , dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org References: <20221209083339.3780776-1-alexander.stein@ew.tq-group.com> <45157029.fMDQidcC6G@steina-w> <6da2330d-516e-7dc4-a000-1e68c7f7887e@denx.de> <2735716.BEx9A2HvPv@steina-w> <9f8b1c17-0bc5-ae99-b7b1-cb2f52f9310d@kontron.de> From: Krzysztof Kozlowski In-Reply-To: <9f8b1c17-0bc5-ae99-b7b1-cb2f52f9310d@kontron.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On 12/12/2022 10:09, Frieder Schrempf wrote: >>>> This does seem like a hardware bug right there, can you double-check >>>> this with the hardware engineer ? >>> >>> Yep, checked with hardware engineer. An 470nF is attached, together >>> with an >>> open drain output and only the internal pull-up. So yes ~113ms rising >>> time >>> until 0.7 x VCC. >> >> I don't suppose you can have that capacitor reduced or better yet, some >> external pull up added, can you ? > > Actually our HW engineers have implemented a similar RC circuit to > provide a hardware delay for the EN signal. I think this is due to a > design note in the datasheet (see chapter 7.4.1) and therefore it's > probably widely spread. If I read section 7.4.1 correctly, it would be enough to just add delay Ten=1ms instead of the capacitor, right? And that would be device-specific. But if one chooses the capacitor solution, it becomes now board specific. Best regards, Krzysztof