6.10/bisected/regression - commits bc87d666c05 and 6d4279cb99ac cause appearing green flashing bar on top of screen on Radeon 6900XT and 120Hz

[Eric Biggers]

On Tue, Jul 16, 2024 at 01:10:37PM -0400, Alex Deucher wrote:
> From 8aaf8da07a8b542c0a0f4da2601da07beddfdeb0 Mon Sep 17 00:00:00 2001
> From: Alex Deucher <alexander.deucher at amd.com>
> Date: Tue, 16 Jul 2024 12:49:25 -0400
> Subject: [PATCH] drm/amd/display: fix corruption with high refresh rates on
>  DCN 3.0
> 
> This reverts commit bc87d666c05a13e6d4ae1ddce41fc43d2567b9a2 and the
> register changes from commit 6d4279cb99ac4f51d10409501d29969f687ac8dc.
> 
> Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3478
> Cc: mikhail.v.gavrilov at gmail.com
> Cc: Rodrigo Siqueira <Rodrigo.Siqueira at amd.com>
> Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
> ---
>  .../drm/amd/display/dc/optc/dcn10/dcn10_optc.c    | 15 +++------------
>  .../drm/amd/display/dc/optc/dcn20/dcn20_optc.c    | 10 ++++++++++
>  2 files changed, 13 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/dc/optc/dcn10/dcn10_optc.c b/drivers/gpu/drm/amd/display/dc/optc/dcn10/dcn10_optc.c
> index 4f82146d94b1..f00d27b7c6fe 100644
> --- a/drivers/gpu/drm/amd/display/dc/optc/dcn10/dcn10_optc.c
> +++ b/drivers/gpu/drm/amd/display/dc/optc/dcn10/dcn10_optc.c
> @@ -950,19 +950,10 @@ void optc1_set_drr(
>  				OTG_FORCE_LOCK_ON_EVENT, 0,
>  				OTG_SET_V_TOTAL_MIN_MASK_EN, 0,
>  				OTG_SET_V_TOTAL_MIN_MASK, 0);
> -
> -		// Setup manual flow control for EOF via TRIG_A
> -		optc->funcs->setup_manual_trigger(optc);
> -
> -	} else {
> -		REG_UPDATE_4(OTG_V_TOTAL_CONTROL,
> -				OTG_SET_V_TOTAL_MIN_MASK, 0,
> -				OTG_V_TOTAL_MIN_SEL, 0,
> -				OTG_V_TOTAL_MAX_SEL, 0,
> -				OTG_FORCE_LOCK_ON_EVENT, 0);
> -
> -		optc->funcs->set_vtotal_min_max(optc, 0, 0);
>  	}
> +
> +	// Setup manual flow control for EOF via TRIG_A
> +	optc->funcs->setup_manual_trigger(optc);
>  }
>  
>  void optc1_set_vtotal_min_max(struct timing_generator *optc, int vtotal_min, int vtotal_max)
> diff --git a/drivers/gpu/drm/amd/display/dc/optc/dcn20/dcn20_optc.c b/drivers/gpu/drm/amd/display/dc/optc/dcn20/dcn20_optc.c
> index 43417cff2c9b..b4694985a40a 100644
> --- a/drivers/gpu/drm/amd/display/dc/optc/dcn20/dcn20_optc.c
> +++ b/drivers/gpu/drm/amd/display/dc/optc/dcn20/dcn20_optc.c
> @@ -453,6 +453,16 @@ void optc2_setup_manual_trigger(struct timing_generator *optc)
>  {
>  	struct optc *optc1 = DCN10TG_FROM_TG(optc);
>  
> +	/* Set the min/max selectors unconditionally so that
> +	 * DMCUB fw may change OTG timings when necessary
> +	 * TODO: Remove the w/a after fixing the issue in DMCUB firmware
> +	 */
> +	REG_UPDATE_4(OTG_V_TOTAL_CONTROL,
> +				 OTG_V_TOTAL_MIN_SEL, 1,
> +				 OTG_V_TOTAL_MAX_SEL, 1,
> +				 OTG_FORCE_LOCK_ON_EVENT, 0,
> +				 OTG_SET_V_TOTAL_MIN_MASK, (1 << 1)); /* TRIGA */
> +
>  	REG_SET_8(OTG_TRIGA_CNTL, 0,
>  			OTG_TRIGA_SOURCE_SELECT, 21,
>  			OTG_TRIGA_SOURCE_PIPE_SELECT, optc->inst,
> -- 
> 2.45.2

This patch fixes the bug for me too.  I am using a Radeon RX 6400, and I've been
encountering the bug when using 1920x1080 resolution on a monitor whose native
resolution is 2560x1440.  Feel free to add:

    Tested-by: Eric Biggers <ebiggers at kernel.org>

Thanks,

- Eric