drm/i915/audio: Prune ELD SADs based on HDMI audio bandwidth

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Add bandwidth check to determine whether a given audio sample rate and
channel count can be carried within the hblank period for HDMI TMDS mode.

Use this check to prune unsupported sample rates from each SAD in the
ELD during intel_audio_compute_config(). SADs with no remaining
supported rates are removed entirely.

Sample rates are pruned rather than channel counts, since compressed
formats (e.g. AC-3) are associated with specific channel counts.

v2:
 - Use DIV64_U64_ROUND_UP() instead of DIV_ROUND_UP_ULL() to avoid
   do_div() truncating the 64-bit divisor to 32-bit, which caused
   audio_packets_line to be wildly inflated and all SADs to be pruned.
 - Guard intel_audio_hdmi_eld_compute_config() against HDMI FRL modes.
   (Remove it when BW calculations for FRL are added.)

v3:
 - Rebase

v4:
 - Rework SAD removal into a single-pass, two-pointer compaction
   instead of memmove-ing the tail on every removal. (Jani)

v5:
 - Drop the FRL guard, i915 doesn't support FRL yet. (Ankit)
 - s/required_tmds/hblank_audio_min (Ankit)
 - Add HDMI_TMDS_AUDIO_PACKETS_LINE_MAX macro
   instead of a magic number 18. (Ankit)
 - Use drm_eld_sad_get()/drm_eld_sad_set() instead of
   raw ELD byte access. (Ankit)
 - Drop extra blank line. (Ankit)

BSpec: 68944
Cc: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Cc: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Vinod Govindapillai <vinod.govindapillai@intel.com>
Cc: Mitul Golani <mitulkumar.ajitkumar.golani@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Assisted-by: GitHub-Copilot:claude-opus-4.6
Signed-off-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Link: https://patch.msgid.link/20260901103639.617757-3-chaitanya.kumar.borah@intel.com

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Chaitanya Kumar Borah 2026-09-01 16:06:39 +05:30

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commit e5e84aaf3e

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drivers/gpu/drm/i915/display/intel_audio.c

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