Re: [PATCH 12/18] pinctrl: bcm2835: Add support for BCM2711 pull-up functionality

[Stefan Wahren <wahrenst@gmx.net>]

Hi Linus,

Am 11.08.19 um 22:15 schrieb Stefan Wahren:
> Am 05.08.19 um 11:38 schrieb Linus Walleij:
>> On Mon, Jul 22, 2019 at 8:24 AM Stefan Wahren <wahrenst@gmx.net> wrote:
>>
>>> The BCM2711 has a new way of selecting the pull-up/pull-down setting
>>> for a GPIO pin. The registers used for the BCM2835, GP_PUD and
>>> GP_PUDCLKn0, are no longer connected. A new set of registers,
>>> GP_GPIO_PUP_PDN_CNTRL_REGx must be used. This commit will add
>>> a new compatible string "brcm,bcm2711-gpio" and the kernel
>>> driver will use it to select which method is used to select
>>> pull-up/pull-down.
>>>
>>> This patch based on a patch by Al Cooper which was intended for the
>>> BCM7211. This is a bugfixed and improved version.
>>>
>>> Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
>> Patch applied.
> Thanks
>> I think I complained about some other version of this patch, this one
>> looks entirely acceptable.
>>
>> Can we get rid of custom pull settings etc from the upstream device
>> trees so we don't set bad examples? I have a strong urge to
>> throw in a pr_warn() about any use of it.
> Ironically, my pre-RFC version tried to convert all BCM2835 pinmux
> settings to generic ones. Unfortunately it seems that i made a mistake,
> because it didn't work as expected. Since we stumpled above more and
> more other issues (not relevant to pinctrl) during upstream review, i
> decided to start with legacy pull-up support, so we can fix this later
> in the devicetree for both platforms (currently BCM2711 uses most of the
> old BCM2835 pinmuxes including the legacy stuff). So yes my plan is to
> fix this soon.

today i had the time to try this out. Instead of the following:

    i2c0_gpio0: i2c0_gpio0 {
        brcm,pins = <0 1>;
        brcm,function = <BCM2835_FSEL_ALT0>;
        brcm,pull = <BCM2835_PUD_UP
                 BCM2835_PUD_OFF>;
    }

you want this?

    i2c0_gpio0: i2c0_gpio0 {
        pin-sda {
            function = "alt0";
            pins = "gpio0";
            bias-pull-up;
        };
        pin-scl {
            function = "alt0";
            pins = "gpio1";
            bias-disable;
        };
    };

Unfortunately i don't know U-Boot is handle the BCM2835 specific pinctrl
functions.

>
> Stefan
>
>> Yours,
>> Linus Walleij