Re: [Intel-gfx] [PATCH] drm/i915: Use 18 fast wake fast wake AUX sync len

[Jani Nikula <jani.nikula@linux.intel.com>]

On Mon, 29 May 2023, Jouni Högander <jouni.hogander@intel.com> wrote:
> HW default for wake sync pulses is 18. 10 precarge and 8 preamble. There is
> no reason to change this especially as it is causing problems with certain
> eDP panels.
>
> Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
> Fixes: 605f7c731333 ("drm/i915: Fix fast wake AUX sync len")

Due to the cherry-picks I think it's better to reference e1c71f8f9180
("drm/i915: Fix fast wake AUX sync len") which has been backported to
stable. We need this fix to go wherever that's been backported.

What happens if we use cc: stable and this gets backported to a kernel
that does *not* have "drm/i915: Fix fast wake AUX sync len"? Any harm in
that?

BR,
Jani.



> Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/8475
> ---
>  drivers/gpu/drm/i915/display/intel_dp_aux.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux.c b/drivers/gpu/drm/i915/display/intel_dp_aux.c
> index 0c27db8ae4f1..197c6e81db14 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_aux.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_aux.c
> @@ -129,7 +129,7 @@ static int intel_dp_aux_sync_len(void)
>  
>  static int intel_dp_aux_fw_sync_len(void)
>  {
> -	int precharge = 16; /* 10-16 */
> +	int precharge = 10; /* 10-16 */
>  	int preamble = 8;
>  
>  	return precharge + preamble;

-- 
Jani Nikula, Intel Open Source Graphics Center