[PATCH RFC 3/3] ARM64: bcm2837-rpi: Fix pwm and i2c pin control

Eric Anholt eric at anholt.net
Mon Feb 27 14:36:48 PST 2017

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

>> Eric Anholt <eric at anholt.net> hat am 27. Februar 2017 um 21:56 geschrieben:
>> Stefan Wahren <stefan.wahren at i2se.com> writes:
>> > According to the firmware DT blob [1] the RPi 3 uses different
>> > pins for i2c0 and pwm.
>> >
>> > [1] - https://github.com/raspberrypi/firmware/blob/master/extra/dt-blob.dts
>> >
>> > Fixes: 9d56c22a7861 ("ARM: bcm2835: Add devicetree for the Raspberry Pi 3.")
>> > Signed-off-by: Stefan Wahren <stefan.wahren at i2se.com>
>> Interesting.  The dt-blob does, I think, basically reflect the state
>> that the pins will be in when the firmware hands off to us.  Note that
>> the firmware also, at boot, sets ID_SDA/SCL to function 0 (i2c0), probes
>> for a HAT ROM and saves it, then restores those pins to whatever mux
>> they had before (presumably the dt-blob pin_config values).
>> Linux doesn't have any HAT probing code itself, so leaving pins 0/1 as
>> GPIO input (most boards) or i2c0 (rev2) should be fine.  I think this
>> patch should effectively be a no-op, unless you've enabled the pwm node.
>> My only suggestion for change is: These pin configurations are
>> board-specific, so could we just move them into the specific board
>> files, instead? 
> Yes, that would be better. In case of pin configurations do you mean
> only those affected by this patch or all pin configurations?

I was just thinking about the ones you're changing in this patch.

>> Basically leave bcm2835-rpi.dtsi as the "generic
>> configuration of bcm283x for the rpi firmware" rather than "things
>> common to bcm2835/6 with rpi firmware but not bcm2837 with rpi
>> firmware".
> If this our intension, shouldn't we rename it to bcm283x-rpi.dtsi?

That sounds good to me.
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