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

[Stefan Wahren]

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):

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++) {