On 09/12/2022 13:02, Marek Vasut wrote: > On 12/9/22 10:36, Alexander Stein wrote: >> Hello Krzysztof, > > Hi, > >> Am Freitag, 9. Dezember 2022, 10:07:45 CET schrieb Krzysztof Kozlowski: >>> 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 <alexander.stein@xxxxxxxxxxxxxxx> >>>>>> --- >>>>>> >>>>>> .../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). > > The chip has two separate input pins: > > VCC -- power supply that's regulator > EN -- reset line, that's GPIO > > Alexander is talking about EN line here. I know, but mainline boards seems to be missing power supply, so that raises questions. Whether voltage on some input pin reaches specified level is hardly a problem of only this bridge. OTOH, datasheet describes another delay which is specific to the chip and which is fixed - t_en/ten/Ten. Best regards, Krzysztof
