Linus Walleij writes:
> Hi Lars,
>
> I'm overall mostly happy with the latest posting (not the one I respond to here)
I'm glad we're getting there :-)
>
> On Thu, Oct 8, 2020 at 12:57 PM Lars Povlsen <lars.povlsen@xxxxxxxxxxxxx> wrote:
>> > On Tue, Oct 6, 2020 at 4:25 PM Lars Povlsen <lars.povlsen@xxxxxxxxxxxxx> wrote:
>
>> >> + gc->of_xlate = microchip_sgpio_of_xlate;
>> >> + gc->of_gpio_n_cells = 3;
>> >
>> > So I'm sceptical to this.
>> >
>> > Why can't you just use the pin index in cell 0 directly
>> > and avoid cell 1?
>> >
>>
>> You scepticism has surfaced before :-). The (now) 2 indices relates to
>> how the hardware address signals.
>>
>> Each signal/pin is addressed by port, bit number and direction. We now
>> have the direction encoded in the bank/phandle.
>
> I'm sorry but I just don't get it, I suppose. To me it is pretty
> straight-forward
> that the cells indicate the pin and then the flags. I do understand you
> need the port at all, since this is implicit from the reg property
> of the DT node. Are these two different things?
I responded to this in your comments to the DT bindings.
I just for got to offer to add a description for "#gpio-cells", I see
that's missing. That should make it "crystal clear" - I hope!
Something like:
--- a/Documentation/devicetree/bindings/pinctrl/microchip,sparx5-sgpio.yaml
+++ b/Documentation/devicetree/bindings/pinctrl/microchip,sparx5-sgpio.yaml
@@ -86,10 +86,17 @@ patternProperties:
gpio-controller: true
'#gpio-cells':
+ description: |
+ Specifies the pin (port and bit) and flags. Note that the
+ SGIO pin is defined by *2* numbers, a port number between 0
+ and 31, and a bit index, 0 to 3. The maximum bit number is
+ controlled indirectly by the "ngpios" property: (ngpios/32).
const: 3
ngpios:
- minimum: 1
+ description: The numbers of GPIO's exposed. This must be a
+ multiple of 32.
+ minimum: 32
maximum: 128
required:
Would that be adequate, or should this also be added as a comment in
microchip_sgpio_of_xlate()?
Like:
+ /* Note that the SGIO pin is defined by *2* numbers, a port
+ * number between 0 and 31, and a bit index, 0 to 3.
+ */
if (gpiospec->args[0] > SGPIO_BITS_PER_WORD ||
gpiospec->args[1] > priv->bitcount)
return -EINVAL;
I hope we can put this one to bed...
---Lars
>
> Yours,
> Linus Walleij
--
Lars Povlsen,
Microchip
