linux-kernel - Re: [PATCH] pinctrl: initialise nsp-mux earlier.

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Date:   Tue, 30 Jun 2020 21:44:35 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Mark Tomlinson <Mark.Tomlinson@...iedtelesis.co.nz>,
        "ray.jui@...adcom.com" <ray.jui@...adcom.com>,
        "bcm-kernel-feedback-list@...adcom.com" 
        <bcm-kernel-feedback-list@...adcom.com>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linus.walleij@...aro.org" <linus.walleij@...aro.org>,
        "sbranden@...adcom.com" <sbranden@...adcom.com>,
        "rjui@...adcom.com" <rjui@...adcom.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pinctrl: initialise nsp-mux earlier.



On 6/30/2020 9:37 PM, Mark Tomlinson wrote:
> On Tue, 2020-06-30 at 20:14 -0700, Florian Fainelli wrote:
>> Sorry, it looks like I made a mistake in my testing (or I was lucky),
>>> and this patch doesn't fix the issue. What is happening is:
>>> 1) nsp-pinmux driver is registered (arch_initcall).
>>> 2) nsp-gpio-a driver is registered (arch_initcall_sync).
>>> 3) of_platform_default_populate_init() is called (also at level
>>> arch_initcall_sync), which scans the device tree, adds the nsp-gpio-a
>>> device, runs its probe, and this returns -EPROBE_DEFER with the error
>>> message.
>>> 4) Only now nsp-pinmux device is probed.
>>>
>>> Changing the 'arch_initcall_sync' to 'device_initcall' in nsp-gpio-a
>>> ensures that the pinmux is probed first since
>>> of_platform_default_populate_init() will be called between the two
>>> register calls, and the error goes away. Is this change acceptable as a
>>> solution?
>>
>> If probe deferral did not work, certainly but it sounds like this is
>> being done just for the sake of eliminating a round of probe deferral,
>> is there a functional problem this is fixing?
> 
> No, I'm just trying to prevent an "error" message appearing in syslog.
> 
>>> The actual error message in syslog is:
>>>
>>> kern.err kernel: gpiochip_add_data_with_key: GPIOs 480..511
>>> (18000020.gpio) failed to register, -517
>>>
>>> So an end user sees "err" and "failed", and doesn't know what "-517"
>>> means.
>>
>> How about this instead:
>>
>> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
>> index 4fa075d49fbc..10d9d0c17c9e 100644
>> --- a/drivers/gpio/gpiolib.c
>> +++ b/drivers/gpio/gpiolib.c
>> @@ -1818,9 +1818,10 @@ int gpiochip_add_data_with_key(struct gpio_chip
>> *gc, void *data,
>>         ida_simple_remove(&gpio_ida, gdev->id);
>>  err_free_gdev:
>>         /* failures here can mean systems won't boot... */
>> -       pr_err("%s: GPIOs %d..%d (%s) failed to register, %d\n", __func__,
>> -              gdev->base, gdev->base + gdev->ngpio - 1,
>> -              gc->label ? : "generic", ret);
>> +       if (ret != -EPROBE_DEFER)
>> +               pr_err("%s: GPIOs %d..%d (%s) failed to register, %d\n",
>> +                       __func__, gdev->base, gdev->base + gdev->ngpio - 1,
>> +                       gc->label ? : "generic", ret);
>>         kfree(gdev);
>>         return ret;
>>  }
>>
> That was one of my thoughts too. I found someone had tried that
> earlier, but it was rejected:
> 
> 
> https://patchwork.ozlabs.org/project/linux-gpio/patch/1516566774-1786-1-git-send-email-david@lechnology.com/

clk or reset APIs do not complain loudly on EPROBE_DEFER, it seems to me
that GPIO should follow here. Also, it does look like Linus was in
agreement in the end, not sure why it was not applied though.
-- 
Florian