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From: Florian Fainelli <f.fainelli@gmail.com>
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>,
	"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>
Subject: Re: [PATCH] pinctrl: initialise nsp-mux earlier.
Date: Tue, 30 Jun 2020 21:44:35 -0700
Message-ID: <cd40f919-f8d9-cde4-6cc5-f523e4973c3b@gmail.com> (raw)
In-Reply-To: <db96187e25342cd36133cde64ef742e03325c8c3.camel@alliedtelesis.co.nz>



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

  reply index

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-30 21:29 Mark Tomlinson
2020-06-30 22:08 ` Ray Jui
2020-07-01  2:23   ` Mark Tomlinson
2020-07-01  3:14     ` Florian Fainelli
2020-07-01  4:37       ` Mark Tomlinson
2020-07-01  4:44         ` Florian Fainelli [this message]
2020-07-06 18:03           ` Ray Jui

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