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

[Sunyun Yang]

Krzysztof Kozlowski <krzk@xxxxxxxxxx> 于2026年6月25日周四 21:51写道：
>
> 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.
>

The lontium-lt9611.yaml uses GPIO_ACTIVE_HIGH. I am just following the
rule of this device tree. If I modify the device tree to use
GPIO_ACTIVE_LOW,
and use the following code in my driver, then my driver would be correct.
However, would the existing kernel drivers lontium-lt9611uxc.c and
lontium-lt9611.c be affected?
static void lt9611c_reset(struct lt9611c *lt9611c)
{
    gpiod_set_value_cansleep(lt9611c->reset_gpio, 1);
    msleep(50);
    gpiod_set_value_cansleep(lt9611c->reset_gpio, 0);
    msleep(20);
}



>
> Best regards,
> Krzysztof