Re: [PATCH RFC V2 3/4] pinctrl: bcm2835: activate strict mux mode

[Stefan Wahren <stefan.wahren@xxxxxxxx>]

Am 21.01.19 um 08:34 schrieb Lukas Wunner:
> On Mon, Jan 21, 2019 at 08:11:24AM +0100, Stefan Wahren wrote:
>> This activates strict mode muxing for the bcm2835 pin controller,
>> as the GPIO Function Select Registers do not allow GPIO and functions
>> at the same time.
> bcm2835_spi_setup() in spi-bcm2835.c converts a native chip select
> to a gpio chip select.  So pins 7+8 and/or 35+36 may be set to
> function alt0 but in reality the pins are requested and driven as
> generic output gpio pins.
>
> I'm not sure but doesn't this break in strict mode?

That's a good point. I hope that isn't a problem because owner should be
the same.

But i didn't test this scenario. Do you mind to give this series a try?

The only issue i found so far was a unnecessary pinctrl on the Raspberry
Pi Zero W, which should be fixed with this [1].

At the end we need to switch to strict mode, because currently a simple
gpioset can "destroy" the mux setting for I2C or SPI.

[1] - https://marc.info/?l=linux-arm-kernel&m=154800402627578

>
> Thanks,
>
> Lukas
>