>Am 2023-04-09 16:25, schrieb Sahin, Okan: >>> Fri, Apr 07, 2023 at 03:48:25PM +0200, Linus Walleij kirjoitti: >>>> On Wed, Apr 5, 2023 at 3:57 PM Michael Walle <michael@xxxxxxxx> >>>> wrote: >>>> >>>> > OTOH I'm not sure the driver is doing it correctly, because it also >>>> > seems to switch the pullup resisters together with the direction. >>>> > I'm not sure that is correct. So there might be just one register >>>> > involved after all and the GPIO_REGMAP should work again. >>>> >>>> I'm pretty sure that should be in the .set_config() callback. >>>> >>>> > Also, according to the datasheet this has some nv memory (to set the >>>> > initial state of the GPIOs [?]). So it should really be a >>>> > multi-function device. I'm not sure if this has to be considered >>>> > right from the beginning or if the device support can start with >>>> > GPIO only and later be transitioned to a full featured MFD (probably with >nvmem >>> support). >>>> >>>> That's a bit of a soft definition. >>>> >>>> If the chip is *only* doing GPIO and nvram it can be a GPIO-only >>>> device I think. >>>> >>>> The precedent is a ton of ethernet drivers with nvram for storing >>>> e.g. >>>> the MAC address. We don't make all of those into MFDs, as the nvram >>>> is >>>> closely tied to the one and only function of the block. >>> >>> I agree with Linus. This should be part of the actual (main) driver >>> for the chip as many >>> do (like USB to serial adapters that have GPIO capability). > >You mean the gpio driver is calling nvmem_register()? Yeah I agree, that >should work. > >> I think gpio_regmap is not suitable for this driver as Michael stated. >> https://www.analog.com/media/en/technical-documentation/data- >sheets/ds4520.pdf >> Please check block diagram. There are two input registers that control >> gpio state >> so gpio_regmap does not look ok for this. Am I missing something? > >You mean F8/F9? That will work as they are for different GPIOs. What >doesn't work with gpio-regmap is when you need to modify two different >registers for one GPIO. Have a look at gpio_regmap_get() and >gpio_regmap_set(). If the default gpio_regmap_simple_xlate() doesn't >work >you can use your own .xlate() op. > Actually, I checked the functions that you suggested, but as far as I understand they might work if there would be one bit to set direction or value. However, this is not the case for ds4520. In other words, if I want to set the gpio direction as output, I need to set a corresponding bit for both F0 and F1 registers. In the document, you can see block diagram. I do not know why, but design is not standard that’s why I think I can not use gpio-regmap. >> Also, at this point I am not planning to add nvmem support. > >That is a pity, because that is the whole use case for this gpio >expander, >no? "Programmable Replacement for Mechanical Jumpers and Switches" I can set "SEE" bit as "0" in the Configuration Register to write EEPROM so it might solve issue. > >-michael Regards, Okan Sahin
