Re: [Intel-gfx] [PATCH] drm/i915/dp: Fix intel_edp_compare_alt_mode.

From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: intel-gfx@lists.freedesktop.org,
	Paulo Zanoni <paulo.r.zanoni@intel.com>,
	Jani Nikula <jani.nikula@intel.com>,
	stable@vger.kernel.org, Rodrigo Vivi <rodrigo.vivi@intel.com>
Subject: Re: [Intel-gfx] [PATCH] drm/i915/dp: Fix intel_edp_compare_alt_mode.
Date: Tue, 13 Mar 2018 15:11:43 +0200	[thread overview]
Message-ID: <20180313131143.GV5453@intel.com> (raw)
In-Reply-To: <20180313092855.32376-1-maarten.lankhorst@linux.intel.com>

On Tue, Mar 13, 2018 at 10:28:55AM +0100, Maarten Lankhorst wrote:
> On fi-cnl-y3 we have 2 modes that differ only by crtc_clock. This means
> that if we request the normal mode, we automatically get the downclocked
> mode.
> 
> This can be seen during boot:
> [drm:drm_helper_probe_single_connector_modes] [CONNECTOR:101:eDP-1] probed modes :
> [drm:drm_mode_debug_printmodeline] Modeline 102:"3840x2160" 60 533250 3840 3888 3920 4000 2160 2163 2168 2222 0x48 0xa
> [drm:drm_mode_debug_printmodeline] Modeline 103:"3840x2160" 48 426600 3840 3888 3920 4000 2160 2163 2168 2222 0x40 0xa
> ...
> [drm:intel_dump_pipe_config [i915]] [CRTC:51:pipe A][modeset]
> [drm:intel_dump_pipe_config [i915]] output_types: EDP (0x100)
> [drm:intel_dump_pipe_config [i915]] cpu_transcoder: EDP, pipe bpp: 24, dithering: 0
> [drm:intel_dump_pipe_config [i915]] dp m_n: lanes: 4; gmch_m: 4970250, gmch_n: 8388608, link_m: 828375, link_n: 1048576, tu: 64
> [drm:intel_dump_pipe_config [i915]] dp m2_n2: lanes: 4; gmch_m: 4970250, gmch_n: 8388608, link_m: 828375, link_n: 1048576, tu: 64
> [drm:intel_dump_pipe_config [i915]] audio: 0, infoframes: 0
> [drm:intel_dump_pipe_config [i915]] requested mode:
> [drm:drm_mode_debug_printmodeline] Modeline 0:"3840x2160" 60 533250 3840 3888 3920 4000 2160 2163 2168 2222 0x48 0xa
> [drm:intel_dump_pipe_config [i915]] adjusted mode:
> [drm:drm_mode_debug_printmodeline] Modeline 0:"3840x2160" 48 426600 3840 3888 3920 4000 2160 2163 2168 2222 0x40 0xa
> 
> Testcase: kms_panel_fitting.atomic-fastset
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Fixes: dc911f5bd8aa ("drm/i915/edp: Allow alternate fixed mode for eDP if available.")
> Cc: David Weinehall <david.weinehall@linux.intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
> Cc: Jani Nikula <jani.nikula@intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Jim Bride <jim.bride@linux.intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: <stable@vger.kernel.org> # v4.14+
> ---
>  drivers/gpu/drm/i915/intel_dp.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 9a4a51e79fa1..0bd3cc1c82b4 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -1684,7 +1684,8 @@ static bool intel_edp_compare_alt_mode(struct drm_display_mode *m1,
>  			m1->vdisplay == m2->vdisplay &&
>  			m1->vsync_start == m2->vsync_start &&
>  			m1->vsync_end == m2->vsync_end &&
> -			m1->vtotal == m2->vtotal);
> +			m1->vtotal == m2->vtotal &&
> +			m1->clock == m2->clock);

Isn't the entire point here to ignore differences in the clock? Hmm.
Maybe not.

Probably what we really want to do is check whether the requested
refresh rate is closer to the fixed mode or the alt mode.

>  	return bres;
>  }
>  
> -- 
> 2.16.2
> 
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-- 
Ville Syrjälä
Intel OTC