[v5 0/2] drm/i915/audio: Add HDMI TMDS audio bandwidth check

[Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>]

This series adds audio bandwidth validation for HDMI TMDS mode.
When the available hblank period cannot carry the required
audio packets for a given sample rate and channel count, the
corresponding frequencies are pruned from the ELD SADs before they reach
the audio driver.

Sample rates are pruned rather than channel counts because compressed
audio formats like Dolby Digital (AC-3) and DTS require a fixed channel
configuration to decode.

This improves on an earlier attempt which can be seen in [1]

[1] https://lore.kernel.org/intel-gfx/20230615063137.2219870-3-mitulkumar.ajitkumar.golani@intel.com/

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.

v3:
 - Rebase

v4:
 - Simply SAD Removal logic (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)

Chaitanya Kumar Borah (2):
  drm/i915/hdmi: Move audio compute config after format selection
  drm/i915/audio: Prune ELD SADs based on HDMI audio bandwidth

 drivers/gpu/drm/i915/display/intel_audio.c | 153 +++++++++++++++++++++
 drivers/gpu/drm/i915/display/intel_hdmi.c  |   8 +-
 2 files changed, 157 insertions(+), 4 deletions(-)

-- 
2.50.1