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 21:17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.



> Best regards,
> Krzysztof