Re: [PATCH AUTOSEL 5.12 42/43] powerpc/fsl: set fsl,i2c-erratum-a004447 flag for P2041 i2c controllers

Sasha Levin [off-list ref] writes:

From: Chris Packham <chris.packham@alliedtelesis.co.nz>

[ Upstream commit 7adc7b225cddcfd0f346d10144fd7a3d3d9f9ea7 ]

The i2c controllers on the P2040/P2041 have an erratum where the
documented scheme for i2c bus recovery will not work (A-004447). A
different mechanism is needed which is documented in the P2040 Chip
Errata Rev Q (latest available at the time of writing).

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Wolfram Sang <wsa@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/powerpc/boot/dts/fsl/p2041si-post.dtsi | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

This patch (and the subsequent one), just set a flag in the device tree.

They have no effect unless you also backport the code change that looks
for that flag, which was upstream commit:

  8f0cdec8b5fd ("i2c: mpc: implement erratum A-004447 workaround")

AFAICS you haven't picked that one up for any of the stable trees.

I'll defer to Chris & Wolfram on whether it's a good idea to take the
code change for stable.

I guess it's harmless to pick these two patches, but it's also
pointless. So I think you either want to take all three, or drop these
two.

cheers