On Sat, May 8, 2021 at 4:20 PM Mark Kettenis <kettenis@xxxxxxxxxxx> wrote: > The Apple GPIO controller is a simple combined pin and GPIO conroller > present on Apple ARM SoC platforms, including various iPhone and iPad > devices and the "Apple Silicon" Macs. > > Signed-off-by: Mark Kettenis <kettenis@xxxxxxxxxxx> I knew this was coming! I saw an earlier version of the Linux pin control driver in some tree somewhere. I see we're only discussing bindings right now, but it would be great to also take a look at the U-Boot driver and scratch Linux driver (which I bet both exist) for a deeper understanding. Git tree web links are fine. > +description: | > + The Apple GPIO controller is a simple combined pin and GPIO controller spelling > + present on Apple ARM SoC platforms, including various iPhone and iPad > + devices and the "Apple Silicon" Macs. > +properties: > + compatible: > + items: > + - const: apple,t8103-pinctrl > + - const: apple,pinctrl So is this an entirely Apple thing now, and not based on some Samsung block from S3C like what we have seen before? It'd be great if Krzysztof or Tomasz who have experience with the Samsung hardware could have a look at the registers etc in the drivers and confirm or clear any relationship to Samsung hardware. This would partly involve trying to keep the pin control bindings similar to Samsungs if there is a relationship. If there is no relationship, then we invent something new. All looks pretty good, but I am suspicious about this: > + interrupts: > + minItems: 1 > + maxItems: 7 Which is used like that. > + interrupt-controller; > + interrupt-parent = <&aic>; > + interrupts = <AIC_IRQ 16 IRQ_TYPE_LEVEL_HIGH>, > + <AIC_IRQ 17 IRQ_TYPE_LEVEL_HIGH>, > + <AIC_IRQ 18 IRQ_TYPE_LEVEL_HIGH>, > + <AIC_IRQ 19 IRQ_TYPE_LEVEL_HIGH>, > + <AIC_IRQ 20 IRQ_TYPE_LEVEL_HIGH>, > + <AIC_IRQ 21 IRQ_TYPE_LEVEL_HIGH>, > + <AIC_IRQ 22 IRQ_TYPE_LEVEL_HIGH>; First it is really odd with 7 of something as in all computer science but I guess there is some explanation for that. What I am really wondering is if these interrupts are hierarchical, i.e. that they match 1-to-1 to a GPIO line. We only (ideally) define the interrupts when it is used by the GPIO block itself, such as when it spawns a cascaded interrupt controller (i.e. you need to read status bits inside the GPIO controller to figure out which line was fired). If the interrupt has a 1-to-1 mapping between GPIO lines and the parent interrupt controller we usually do not define these interrupts in the device tree at all. In those cases the interrupt is considered hierarchical and we rely on the compatible for the block to define how the interrupt lines are routed to the parent interrupt controller (in this case AIC). In the Linux case, the GPIO driver has a hardcoded table of mappings from the GPIO irq line offset and the corresponding index on the parent interrupt controller (AIC). This is reflected in this IRQ routing information missing from the bindings. Marc Zyngier can probably tell the story of why it is handled like this, There is some info on hierarchical IRQ handling in the Linux GPIO driver docs: https://www.kernel.org/doc/html/latest/driver-api/gpio/driver.html Section "GPIO drivers providing IRQs" Yours, Linus Walleij
