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[88.156.142.67]) by smtp.gmail.com with ESMTPSA id cf27-20020a056512281b00b0049fff3f645esm175958lfb.70.2022.12.09.01.07.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 09 Dec 2022 01:07:46 -0800 (PST) Message-ID: Date: Fri, 9 Dec 2022 10:07:45 +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: Alexander Stein , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , David Airlie , Daniel Vetter , Rob Herring , Krzysztof Kozlowski Cc: Marek Vasut , Frieder Schrempf , dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org References: <20221209083339.3780776-1-alexander.stein@ew.tq-group.com> <20221209083339.3780776-2-alexander.stein@ew.tq-group.com> <07fbe219-9034-65f6-963a-037de9bb6d79@linaro.org> <7463917.EvYhyI6sBW@steina-w> From: Krzysztof Kozlowski In-Reply-To: <7463917.EvYhyI6sBW@steina-w> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On 09/12/2022 09:54, Alexander Stein wrote: > Hello Krzysztof, > > thanks for the fast feedback. > > Am Freitag, 9. Dezember 2022, 09:39:49 CET schrieb Krzysztof Kozlowski: >> On 09/12/2022 09:33, Alexander Stein wrote: >>> It takes some time until the enable GPIO has settled when turning on. >>> This delay is platform specific and may be caused by e.g. voltage >>> shifts, capacitors etc. >>> >>> Signed-off-by: Alexander Stein >>> --- >>> >>> .../devicetree/bindings/display/bridge/ti,sn65dsi83.yaml | 4 ++++ >>> 1 file changed, 4 insertions(+) >>> >>> diff --git >>> a/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi83.yaml >>> b/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi83.yaml >>> index 48a97bb3e2e0d..3f50d497cf8ac 100644 >>> --- a/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi83.yaml >>> +++ b/Documentation/devicetree/bindings/display/bridge/ti,sn65dsi83.yaml >>> >>> @@ -32,6 +32,10 @@ properties: >>> maxItems: 1 >>> description: GPIO specifier for bridge_en pin (active high). >>> >>> + ti,enable-delay-us: >>> + default: 10000 >>> + description: Enable time delay for enable-gpios >> >> Aren't you now mixing two separate delays? One for entire block on (I >> would assume mostly fixed delay) and one depending on regulators >> (regulator-ramp-delay, regulator-enable-ramp-delay). Maybe you miss the >> second delays in your power supply? If so, the first one might be fixed >> and hard-coded in the driver? > > Apparently there are two different delays: reset time (t_reset) of 10ms as > specified by datasheet. This is already ensured by a following delay after > requesting enable_gpio as low and switching the GPIO to low in disable path. > > When enabling this GPIO it takes some time until it is valid on the chip, this > is what this series is about. It's highly platform specific. > > Unfortunately this is completely unrelated to the vcc-supply regulator. This > one has to be enabled before the enable GPIO can be enabled. So there is no > regulator-ramp-delay. Your driver does one after another - regulator followed immediately by gpio - so this as well can be a delay from regulator (maybe not ramp but enable delay). Best regards, Krzysztof