Hi Andy, >On Thu, Dec 14, 2023 at 03:35:18PM +0100, Michael Walle wrote: > >> > > >> >> This driver enables configuration of GPIO direction, GPIO >> > > >> >> values, GPIO debounce settings and handles GPIO interrupts. >> > > >> > >> > > >> >Why gpio-regmap can't be used? >> > > >> >> > > >> I will try to use gpio-remap in the next version. >> > > > >> > > >If it appears that it makes code uglier / complicated, please add >> > > >the note somewhere to answer the above question. >> > > >> > > I've traced the gpio-regmap.c file. It appears that for the driver >> > > to register gpio_irq_chip, it must create the irq_domain and add >> > > it into gpio_regmap_config. >> > > Additionally, the driver needs to register the irq handler by itself. >> > > However, this process can be managed by the gpiolib if the driver >> > > fills in the struct gpio_irq_chip inside struct gpio_chip before >> > > invoking gpiochip_add_data. >> > >> > Hmm... I thought this is solvable issue. >> > Michael, is there a limitation in GPIO regmap that this driver can't >> > be converted? >> >> gpio-regmap is designed that regmap-irq (drivers/base/regmap/irq.c) >> can be used. So, if regmap-irq fit this driver, then it can be used >> together with gpio-regmap. >> >> From a quick glance at the patch, it looks like the gpio portion might >> fit gpio-regmap. >> >> > > Moreover, apart from managing the registers for gpio direction and >> > > value, there are several other registers that require >> > > access(interrupt enable, debounce...). >> > > The GPIO IRQ status registers are located at different base >> > > addresses and are not contiguous. It may need to create an >> > > additional regmap and assign the access table to this regmap. >> > >> > AFAIK this is not a problem as you can provide your own xlate >> > function that will take care about register mapping. >> >> Just for the gpio part. IIRC regmap has it own translation (regmap fields). >> >> > > With the above consideration, I tend to keep using the existing >> > > method. >> > >> > I would like to hear from Michael if it's indeed a big obstacle. >> >> So, regarding the irq portion, again, it must fit the regmap-irq. For >> the additional requirement to set the debounce, you can add a >> .set_config to gpio_regmap_config and supply your own set_config callback. >See also [1]. > >Thank you, Michael, for the prompt answer. It's insightful to me, I will try to >remember these aspects for the future reviews. > >> [1] >> >https://lore.kernel.org/linux-gpio/d4a6a640c373b6d939e147691efa596c@wa >> lle.cc/ > I have looked into regmap-irq, it appears that using the default irq thread_fn(regmap_irq_thread) is required. However, due to hardware limitation, we need to inspect the IRQ_TYPE to determine whether to manage the irq within the irq handler. I think our irq portion does not perfectly fit the regmap-irq. Moreover, it seems that the gpio-regmap.c file needs to be modified if the GPIO driver requires debounce settings. I think the gpio-regmap may not be appropriate for our driver. Do you have any suggestions? Thanks, Tzuyi Chang
