Re: [PATCH] i2c: i2c-gpio: fix some of gpio sleep issues

[Ben Dooks <ben.dooks-4yDnlxn2s6sWdaTGBSpHTA@public.gmane.org>]

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On 27/03/15 17:46, Wolfram Sang wrote:
> On Tue, Mar 17, 2015 at 12:04:29PM +0000, Ben Dooks wrote:
>> The i2c-gpio driver can be used in systems where the GPIO itself
>> is provided by a GPIO driver that may be sleeping (for example,
>> SPI or USB). In this case, it is preferable to use the
>> _cansleep() variants of the GPIO code.
>> 
>> We can only fix this up for the case where the i2c-gpio
>> implementation provides open-drain outputs as there are no
>> gpio_direction_xxx_cansleep() provided.
>> 
>> This removes the issues on the customer system with the console
>> constantly showing the following warning:
>> 
>> WARNING: CPU: 0 PID: 1 at drivers/gpio/gpiolib.c:2389
>> gpiod_set_raw_value
> 
> ??? It will silence a warning but will totally break the timing in
> case sleeping is needed? I'd think the warning is very suitable.

This basically causes our system to fail to boot in any suitable time.

The problem is that the i2c bus is on the end of an SPI bus which means
that the identification EEPROM tests and other items read from it will
run through a gpio chip that is marked as 'can sleep'.

I don't have the exact times, but I got bored after the first thirty
seconds of these log messages and immediately patched them out of the
kernel.

- -- 
Ben Dooks				http://www.codethink.co.uk/
Senior Engineer				Codethink - Providing Genius
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