linux-kernel - Re: [PATCH] pinctrl-zynq: Initialize early

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Message-ID: <5631E019.5040906@xilinx.com>
Date:	Thu, 29 Oct 2015 10:00:09 +0100
From:	Michal Simek <michal.simek@...inx.com>
To:	Sören Brinkmann <soren.brinkmann@...inx.com>,
	"Mike Looijmans" <mike.looijmans@...ic.nl>,
	Linus Walleij <linus.walleij@...aro.org>
CC:	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pinctrl-zynq: Initialize early

Hi Linus,

On 10/23/2015 07:44 AM, Sören Brinkmann wrote:
> On Fri, 2015-10-23 at 07:31AM +0200, Mike Looijmans wrote:
>> On 22-10-15 18:07, Sören Brinkmann wrote:
>>> Hi Mike,
>>>
>>> On Thu, 2015-10-22 at 01:30PM +0200, Mike Looijmans wrote:
>>>> Supplying pinmux configuration for e.g. gpio pins leads to deferred
>>>> probes because the pinctrl device is probed much later than gpio.
>>>> Move the init call to a much earlier stage so it probes before the
>>>> devices that may need it.
>>>>
>>>> Signed-off-by: Mike Looijmans <mike.looijmans@...ic.nl>
>>>
>>> in general, the change should be OK, but neither on zc702 nor zc706 do I
>>> see a difference in respect to deferred probes. With and without the
>>> patch I see:
>>>     root@...q:~# dmesg | grep -i defer
>>>     [    0.097021] zynq-gpio e000a000.gpio: could not find pctldev for node /amba/slcr@...00000/pinctrl@.../gpio0-default, deferring probe
>>>     root@...q:~#
>>>
>>> If you have a case this patch improves things though, feel free to add my
>>> Tested-by: Sören Brinkmann <soren.brinkmann@...inx.com>
>>>
>>
>> On the Florida boards there are i2c controlled clocks, power supplies and
>> reset signals. Replacing the Cadence I2C controller with a GPIO-bitbang
>> controller solved the I2C problems but caused a storm of dozens of deferred
>> probes because of the pinmux driver arriving even after the first probe
>> attempt of the i2c bus driver. Moving the pinmux driver to an earlier stage
>> solved that problem neatly, now the "zynq-pinctrl 700.pinctrl: zynq pinctrl
>> initialized" message appears after the OCM driver.
> 
> OK, makes sense. Thanks for the background.
> 
>> Judging from your comment the GPIO driver still probes earlier (I don't have
>> any GPIO-only pinmuxes yet), so maybe we should amend the patch to probe
>> even earlier. The pinmux driver doesn't depend on anything, so it can
>> potentially probe very early. What do you think?
> 
> I'm pretty neutral on this one :) Hasn't the probe deferral mechanism
> been introduced to avoid having to create ordering through the initcall
> stages? But I agree, having the probe deferral notices is not particularly
> pretty. So, I'd definitely not oppose changing this.
> Though, there is one dependency on the SLCR regmap, but that is initialized
> fairly early.

Any comment on this one?

Thanks,
Michal

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