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SubjectRe: [PATCH v6 03/15] pinctrl: bcm: add bcm63xx base code
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Hi Rob and Linus,

El 11/03/2021 a las 17:13, Linus Walleij escribió:
> On Thu, Mar 11, 2021 at 3:58 PM Rob Herring <robh+dt@kernel.org> wrote:
>> On Wed, Mar 10, 2021 at 6:09 PM Linus Walleij <linus.walleij@linaro.org> wrote:
>>> On Wed, Mar 10, 2021 at 6:51 PM Rob Herring <robh+dt@kernel.org> wrote:
>>>
>>>>> +static const struct of_device_id bcm63xx_gpio_of_match[] = {
>>>>> + { .compatible = "brcm,bcm6318-gpio", },
>>>>> + { .compatible = "brcm,bcm6328-gpio", },
>>>>> + { .compatible = "brcm,bcm6358-gpio", },
>>>>> + { .compatible = "brcm,bcm6362-gpio", },
>>>>> + { .compatible = "brcm,bcm6368-gpio", },
>>>>> + { .compatible = "brcm,bcm63268-gpio", },
>>>>
>>>> All these would be moved to gpio-mmio.c (or maybe that can have a
>>>> fallback compatible?).
>>>
>>> This is gpio-regmap.c and it can only be used as a library
>>> by a certain driver. gpio-mmio.c can be used stand-alone
>>> for certain really simple hardware (though most use that
>>> as a library as well).
>>
>> I don't really care which one is used, but the problem is that this
>> choice is leaking into the binding design.
>
> Aha I guess I misunderstood your comment.
>
>> The primary problem here is
>> once someone uses regmap, then they think they must have a syscon and
>> can abandon using 'reg' and normal address properties as Linux happens
>> to not use them (currently). I think we really need some better regmap
>> vs. mmio handling to eliminate this duplication of foo-mmio and
>> foo-regmap drivers and difference in binding design. Not sure exactly
>> what that looks like, but basically some sort of 'reg' property to
>> regmap creation.
>
> I see the problem. Yeah we should try to be more strict around
> these things. To me there are syscons and "other regmaps",
> where syscon is a real hurdle of registers while "other regmaps"
> are just regmaps by convenience.
>
> Documentation/devicetree/bindings/mfd/syscon.yaml
> describes what a syscon really is so if everyone could
> just read the documentation that would be great ...
>
>> Given we already have a Broadcom GPIO binding for what looks to be
>> similar to this one, I'm left wondering what's the real difference
>> here?
>
> Which one is similar? I can take a look.

@Linus I think @Rob is referring to brcm,bcm6345-gpio:
https://github.com/torvalds/linux/blob/a74e6a014c9d4d4161061f770c9b4f98372ac778/drivers/gpio/gpio-mmio.c#L686

However, the real difference between BCM6345 (and BCM6338) is that these
SoCs have no pin controller at all, only a GPIO controller:

BCM6345:
typedef struct GpioControl {
uint16 unused0;
byte unused1;
byte TBusSel;
uint16 unused2;
uint16 GPIODir;
byte unused3;
byte Leds;
uint16 GPIOio;
uint32 UartCtl;
} GpioControl;

BCM6338:
typedef struct GpioControl {
uint32 unused0;
uint32 GPIODir; /* bits 7:0 */
uint32 unused1;
uint32 GPIOio; /* bits 7:0 */
uint32 LEDCtrl;
uint32 SpiSlaveCfg;
uint32 vRegConfig;
} GpioControl;

BCM6348 and newer also have pinctrl.
That's the main difference between that driver @Rob's referring to and
the ones in this patch series.

>
> We currently have four Broadcom GPIO bindings,
> which are stand alone GPIO blocks and eight Broadcom
> pin controllers that all do GPIO as well.
>
> This family of pin controllers are (as per subject) is
> the bcm63xx series which is a MIPS-based family of SoCs
> found in routers, top bindings in
> Documentation/devicetree/bindings/mips/brcm/soc.txt
> These all have a GPIO block as part of the pin controller
> and the GPIO block is a distinct sub-function of the
> pin controller, and it has up to 32 GPIOs per block,
> hence it has its own subnode inside the pin controller.
>
> This driver follows the pattern of the Ingenic
> pin controller, another MIPS SoC:
> Documentation/devicetree/bindings/pinctrl/ingenic,pinctrl.yaml
>
> Another SoC with several GPIO blocks inside the pin
> controller is SparX5 and that also follows this pattern:
> Documentation/devicetree/bindings/pinctrl/microchip,sparx5-sgpio.yaml
> (This has an example with more than one GPIO block
> inside the pin controller.)
>
> Yours,
> Linus Walleij
>

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