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Subject: Re: [PATCH] pinctrl: initialise nsp-mux earlier.
To:     Florian Fainelli <f.fainelli@gmail.com>,
        Mark Tomlinson <Mark.Tomlinson@alliedtelesis.co.nz>,
        "bcm-kernel-feedback-list@broadcom.com" 
        <bcm-kernel-feedback-list@broadcom.com>,
        "linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>,
        "linus.walleij@linaro.org" <linus.walleij@linaro.org>,
        "sbranden@broadcom.com" <sbranden@broadcom.com>,
        "rjui@broadcom.com" <rjui@broadcom.com>
Cc:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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 <cd40f919-f8d9-cde4-6cc5-f523e4973c3b@gmail.com>
From:   Ray Jui <ray.jui@broadcom.com>
Message-ID: <b0f14acc-fcb1-9e29-e95a-902640d3dff9@broadcom.com>
Date:   Mon, 6 Jul 2020 11:03:45 -0700
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On 6/30/2020 9:44 PM, Florian Fainelli wrote:
> 
> 
> 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.
> 

I think either we silently drop this or we explicitly make it obvious
that it failed due to EPROBE_DEFER. Both seem acceptable to me.

Thanks!

Ray