[PATCH] pinctrl: bcm2835: reduce GPPUD set-up time

[Eric Anholt]

Stefan Wahren <stefan.wahren at i2se.com> writes:

> Since the BCM2835 datasheet doesn't exactly specify the set-up time for
> the GPIO Pull-up/down Clock Registers there was an assumption of 150 cycles
> at a clock rate of 1 MHz. During a discussion [1] in the Raspberry Pi forum
> it turns out that clock rate refers to the VPU which has a rate of 250 MHz.
> So we can reduce the delay to a sensible value and update the comment above.
>
> I tested this optimization with a Raspberry Pi B and a multimeter.
>
> [1] - https://www.raspberrypi.org/forums/viewtopic.php?f=72&t=163352
>
> Signed-off-by: Stefan Wahren <stefan.wahren at i2se.com>

I've confirmed that the only clock input to the hardware module that
contains the GPPUD registers is the VPU clock, and I don't see anything
else over in the pads area either.

Reviewed-by: Eric Anholt <eric at anholt.net>
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