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

[Sunyun Yang]

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.

>
> > Best regards,
> > Krzysztof