On Wed, Jan 6, 2021 at 7:06 PM Maxime Ripard [off-list ref] wrote:

On Mon, Jan 04, 2021 at 10:54:19AM +0000, André Przywara wrote:

quoted

On 03/01/2021 10:00, Samuel Holland wrote:

quoted

On boards where the only peripheral connected to PL0/PL1 is an X-Powers
PMIC, configure the connection to use the RSB bus rather than the I2C
bus. Compared to the I2C controller that shares the pins, the RSB
controller allows a higher bus frequency, and it is more CPU-efficient.

But is it really necessary to change the DTs for those boards in this
way? It means those newer DTs now become incompatible with older
kernels, and I don't know if those reasons above really justify this.

I understand that we officially don't care about "newer DTs on older
kernels", but do we really need to break this deliberately, for no
pressing reasons?

P.S. I am fine with supporting RSB on H6, and even using it on new DTs,
just want to avoid breaking existing ones.

Doing so would also introduce some inconsistencies, one more thing to
consider during reviews, and would require more testing effort.

I'm not sure that stretching our - already fairly sparse - resources
thin would be very wise here, especially for something that we don't
have to do and for a setup that isn't really used that much.

As soon as some software component starts running RSB, (which I assume
is what Samuel is planning to do in Crust?), there's a chance that it
doesn't switch the chip back to I2C. And then Linux won't be able to
access it.

So I'm for keeping things consistent and converting all users to RSB.


ChenYu