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

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Date:	Fri, 23 Oct 2015 07:43:15 +0200
From:	Mike Looijmans <mike.looijmans@...ic.nl>
To:	Sören Brinkmann <soren.brinkmann@...inx.com>
CC:	<git@...inx.com>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pinctrl-zynq: Initialize early

On 23-10-15 07:31, 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.
> 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?

Minor addition:
The gpio-zynq driver probes at "postcore_initcall", so to beat that, the 
zynq-pinmux driver should move to "core_initcall" (instead of 
"arch_initcall"). That would make the gpio deferral go away.

An alternative would be to move the gpio driver to "arch", then "postcore" 
would be enough for the pinmux. If the gpio probe gets deferred, it apparently 
has already been moved to below "subsys" already, with aparently no ill effects.

Mike.


Kind regards,

Mike Looijmans
System Expert

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