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Subject: Re: [PATCH] pinctrl: initialise nsp-mux earlier.
To:     Mark Tomlinson <Mark.Tomlinson@alliedtelesis.co.nz>,
        "ray.jui@broadcom.com" <ray.jui@broadcom.com>,
        "bcm-kernel-feedback-list@broadcom.com" 
        <bcm-kernel-feedback-list@broadcom.com>,
        "linus.walleij@linaro.org" <linus.walleij@linaro.org>,
        "linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>,
        "sbranden@broadcom.com" <sbranden@broadcom.com>,
        "rjui@broadcom.com" <rjui@broadcom.com>
Cc:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
References: <20200630212958.24030-1-mark.tomlinson@alliedtelesis.co.nz>
 <a1dc8f14-187d-a804-45bb-d1fa25ff7b01@broadcom.com>
 <760595a8cdfeb0156d5180ecaeb2ee4487f50cc7.camel@alliedtelesis.co.nz>
From:   Florian Fainelli <f.fainelli@gmail.com>
Message-ID: <86c009a8-05c4-40a3-daef-6d9e848642a3@gmail.com>
Date:   Tue, 30 Jun 2020 20:14:37 -0700
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On 6/30/2020 7:23 PM, Mark Tomlinson wrote:
> On Tue, 2020-06-30 at 15:08 -0700, Ray Jui wrote:
>> May I know which GPIO driver you are referring to on NSP? Both the iProc
>> GPIO driver and the NSP GPIO driver are initialized at the level of
>> 'arch_initcall_sync', which is supposed to be after 'arch_initcall' used
>> here in the pinmux driver
> 
> 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?

> 
>>> though the probe will succeed when the driver is re-initialised, the
>>> error can be scary to end users. To fix this, change the time the
>>
>> Scary to end users? I don't know about that. -EPROBE_DEFER was
>> introduced exactly for this purpose. Perhaps users need to learn what
>> -EPROBE_DEFER errno means?
> 
> 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;
 }

-- 
Florian