Re: [PATCH 4/5] drm/i915/gmbus: Fix i2c bit banging for PTL+

[Sebastian Brzezinka <sebastian.brzezinka@intel.com>]

On Thu Oct 8, 2026 at 12:23 AM CEST, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> The current implementation of w/a 16025573575 does not actually work.
> The GPIO register mask bits are write only, and thus he read-modify-write
> cycles we do will not preserve them. Furthermore the implementation makes
> no effort to preserve the actual direction/output value bits, which is
> a must if all the mask bits were actually set all the time.
>
> Rewrite the whole thing so that we always set all the mask bits,
> and correctly preserve the previous state of the direction/output value
> bits. And do that on all platforms so that we only have a single codepath
> to worry about. As a bonus this approach will also make the code
> work on upcoming platforms where the mask bits no longer even exist.
>
> Smoke tested on alm,cl,tgl,lnl,ptl.
>
> Fixes: 7565fd5dcb0b ("drm/i915/gmbus: Add Wa_16025573575 for PTL/WCL for bit-bashing")
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
Reviewed-by: Sebastian Brzezinka <sebastian.brzezinka@intel.com>
-- 
Best regards,
Sebastian