DTB backward/forward compatibility with "pinctrl: bcm2835: Change init order for gpio hogs"

[Florian Fainelli]

On 3/8/22 11:13 AM, Stefan Wahren wrote:
> Am 07.03.22 um 12:38 schrieb Stefan Wahren:
>> Hi,
>>
>> Am 06.03.22 um 17:54 schrieb Florian Fainelli:
>>> Hi Stefan,
>>>
>>> On 3/6/2022 7:03 AM, Stefan Wahren wrote:
>>>> Hi Florian,
>>>>
>>>> it seems that other platform stumbled on the same issue:
>>>>
>>>> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?h=next-20220304&id=9b4924da4711674e62d97d4f5360446cc78337af
>>>>
>>>>
>>>> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?h=next-20220304&id=7ed07855773814337b9814f1c3e866df52ebce68
>>>>
>>>>
>>>> I will try to prepare a patch.
>>> Thank you! Do you think we could have a core function expose which
>>> would do essentially avoid drivers having to sprinkle checks for the
>>> absence of a 'gpio-ranges' property?
>> unfortunately my first attempts to implement it similiar to the
>> solutions above failed. I read the explanations from the original fix
>> from Christian Lamparter [1] and from my understanding the backward
>> compatibility must be implemented into gpiochip_add_data() or a variant.
>> Before the gpiochip is not registered and afterwards it would be too late.
>>
>> My test scenario (worst case) is an additional gpio hog for the
>> Raspberry Pi 3 B with removed gpio-ranges:
>>
> Not sure this is the right place, but the following hack make the
> Raspberry Pi boot for the defined worst case szenario (no gpio-ranges
> but at least one gpio-hog):

This worked with 'gpio-ranges' as well as without a 'gpio-ranges', the
kernel did warn as you added the message:

[    0.588730] /rdb/gpio at 2200000: gpio-ranges missing. Try to fallback!

and gpio-ranges was the same before/after the patch:

# cat /sys/kernel/debug/pinctrl/47e200000.gpio-pinctrl-bcm2711/gpio-ranges
GPIO ranges handled:
0: pinctrl-bcm2711 GPIOS [4294967295 - 56] PINS [0 - 57]
0: pinctrl-bcm2711 GPIOS [454 - 511] PINS [0 - 57]
#


thanks a lot Stefan!

> 
> diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
> 
> index 91dcf2c..23386dd 100644
> --- a/drivers/gpio/gpiolib-of.c
> +++ b/drivers/gpio/gpiolib-of.c
> @@ -933,6 +933,24 @@ static int of_gpiochip_add_pin_range(struct
> gpio_chip *chip
> )
>         if (!np)
>                 return 0;
>  
> +       if (!of_property_read_bool(np, "gpio-ranges")) {
> +               pr_warn("%pOF: gpio-ranges missing. Try to fallback!\n",
> np);
> +
> +               pctldev = of_pinctrl_get(np);
> +               of_node_put(np);
> +
> +               if (!pctldev)
> +                       return 0;
> +
> +               gpiochip_add_pin_range(chip,
> +                               pinctrl_dev_get_devname(pctldev),
> +                               0,
> +                               0,
> +                               chip->ngpio);
> +
> +               return 0;
> +       }
> +
>         group_names = of_find_property(np, group_names_propname, NULL);
>  
>         for (;; index++) {
> 


-- 
Florian