On Fri, Jun 26, 2026 at 10:15:03AM +0800, Sunyun Yang wrote: > Krzysztof Kozlowski <[email protected]> 于2026年6月25日周四 21:51写道： > > > > On 25/06/2026 15:40, Sunyun Yang wrote: > > > Sunyun Yang <[email protected]> 于2026年6月25日周四 21:26写道： > > >> > > >> Krzysztof Kozlowski <[email protected]> 于2026年6月25日周四 21:17写道： > > >>> > > >>> On 25/06/2026 15:14, Sunyun Yang wrote: > > >>>> Krzysztof Kozlowski <[email protected]> 于2026年6月25日周四 20:54写道： > > >>>>> > > >>>>> On 08/05/2026 15:40, [email protected] 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?
It might, but then it's a DT problem. The GPIO API for drivers always considers the logical state of a GPIO, so if you need to assert a signal, you'll always need to set 1. That's what Krzysztof was trying to explain. The DT will provide with GPIO_ACTIVE_* how that logical state translates to a physical GPIO state. If the DT says that this particular GPIO is active-high, then it means that we need to set the GPIO to 1 to assert reset. Now of course, it might not make sense for the controller itself, but it might for the board if there's a GPIO inverter in the middle for example. Anyway, in the case you're raising, the issue definitely lies in the DT, and that's what would need to be fixed. I also wouldn't be too concerned about lontium-lt9611.yaml, it's just an example. Maxime
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