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

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Date:	Fri, 23 Oct 2015 07:31:25 +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 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?

Mike.


Kind regards,

Mike Looijmans
System Expert

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