Re: [PATCH v6 2/2] drm/bridge: Add Lontium LT9611C(EX/UXD) MIPI DSI to HDMI driver

[Krzysztof Kozlowski]

On 25/06/2026 15:40, Sunyun Yang wrote:
> Sunyun Yang <syyang@xxxxxxxxxxx> 于2026年6月25日周四 21:26写道：
>>
>> Krzysztof Kozlowski <krzk@xxxxxxxxxx> 于2026年6月25日周四 21:17写道：
>>>
>>> On 25/06/2026 15:14, Sunyun Yang wrote:
>>>> Krzysztof Kozlowski <krzk@xxxxxxxxxx> 于2026年6月25日周四 20:54写道：
>>>>>
>>>>> On 08/05/2026 15:40, syyang@xxxxxxxxxxx wrote:
>>>>>> +
>>>>>> +static void lt9611c_reset(struct lt9611c *lt9611c)
>>>>>> +{
>>>>>> +     gpiod_set_value_cansleep(lt9611c->reset_gpio, 1);
>>>>>> +     msleep(20);
>>>>>> +
>>>>>> +     gpiod_set_value_cansleep(lt9611c->reset_gpio, 0);
>>>>>> +     msleep(20);
>>>>>> +
>>>>>> +     gpiod_set_value_cansleep(lt9611c->reset_gpio, 1);
>>>>>
>>>>> This is just plain wrong. Why do you assert, then de-assert and then
>>>>> finally assert AGAIN the reset leaving the device in powerdown stage?
>>>>>
>>>> I am using software to emulate the hardware RESET button on our EVB.
>>>> When the hardware RESET button is pressed while our chip is running,
>>>> the signal level changes from HIGH to LOW and then back to HIGH.
>>>>
>>>> Of course, we can also use the following:
>>>> static void lt9611c_reset(struct lt9611c *lt9611c)
>>>> {
>>>>     gpiod_set_value_cansleep(lt9611c->reset_gpio, 0);
>>>>     msleep(50);
>>>>     gpiod_set_value_cansleep(lt9611c->reset_gpio, 1);
>>>>     msleep(20);
>>>> }
>>>
>>> Makes no sense either and you just did not get the point and did not
>>> answer my question. I asked WHY you leave asserted. Answer "we emulate"
>>> is just plain wrong.
>>>
>>> So again please answer:
>>>
>>> Why do you leave device with reset asserted?
>>>
>>
>>  devicetree:   reset-gpios = <&tlmm 128 GPIO_ACTIVE_HIGH>;
>>
>> GPIO_ACTIVE_HIGH:
>>
>> gpiod_set_value_cansleep(lt9611c->reset_gpio, 0);   ------   reset pin
>> is Low level : Clear the register configuration in the chip to stop
>> the chip from working.
>>
>> gpiod_set_value_cansleep(lt9611c->reset_gpio, 1);   ------  reset pin
>> is high level:  The chip resumes operation.
>>
>>
> 
> Our purpose is: pull the level low to clear the register configuration
> in the chip, and then pull it high to allow the MCU inside the chip to
> re‑initialize the registers.


And you do completely opposite... so that confirms your code is just wrong.


Best regards,
Krzysztof