[PATCH 1/2] dt-bindings: drm/bridge: ti-sn65dsi83: Add enable delay property

[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 at ew.tq-group.com>
>>> ---
>>>
>>>  .../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