soundwire: amd: Add BRA/BPT firmware download support

Add Bulk Register Access (BRA) / Bulk Payload Transport (BPT) support
for AMD SoundWire platforms. This enables high-speed firmware download
to SoundWire peripherals via DP0, using the ACP BRA DMA engine.

Key design points:

- Uses the SoundWire stream framework (sdw_prepare_stream,
  sdw_enable_stream, sdw_disable_stream, sdw_deprepare_stream)
  for all DP0 port programming and bank switches. No manual DP0
  register writes or bank mirrors are needed.

- BRA transport parameters (hstart, hstop, SampleInterval,
  BytesPerFrame) are computed dynamically from the current bus
  frame shape, not hardcoded.

- The ACP BPT DMA engine is triggered by the bank switch
  performed inside sdw_enable_stream(), and stopped by the
  bank switch in sdw_disable_stream().

- Non-contiguous firmware sections are handled by iterating
  per-section: large sections use BRA DMA, small sections
  (< one BRA frame) fall back to sdw_nwrite/sdw_nread.

- BPT stream m_rt entries are skipped in audio compute_params
  to prevent BPT transport parameters from corrupting audio
  port block offset calculations.

- DP0 port_params, xport_params, and port_enable callbacks
  return early for BPT streams since the ACP BRA descriptor
  registers handle DP0 configuration independently.

- bus->bpt_stream is published with WRITE_ONCE() only after the stream
  runtime is added and bpt_stream_refcount is raised under bus_lock, and
  is cleared before the runtime is removed and the stream is freed, so
  the lockless DP0 port callbacks never observe a half-initialised or
  freed stream pointer.

- bus->bpt_fw_download is set around the transfer so sdw_master_rt_alloc()
  admits the BPT allocation while audio streams on the same bus are
  allocated but idle (for example an amplifier left DISABLED across a
  power-off-mode suspend that must re-download firmware on resume). It is
  cleared on the close and open error paths. An audio stream that is
  actively using the bus still blocks the transfer.

- On an aborted or timed-out transfer the ACP BPT DMA engine is disarmed
  (PORT_EN=0) before the sdw_disable_stream() bank switch, so the bank
  switch cannot re-trigger a DMA write into the buffer that is freed once
  the transfer returns.

- A per-manager bpt_lock serialises concurrent BPT transfers
  from multiple slave probes. pm_runtime keeps the bus clock
  active during transfers.

- PTE-based ACP ATU mapping provides DMA scatter-gather for the
  firmware buffer. The ATU maps up to 512 4KB pages (2 MB per
  transfer); each transfer is additionally bounded by the SoundWire
  BPT limit of 1 MB (SDW_BPT_MSG_MAX_BYTES), which the driver enforces.

Signed-off-by: Syed Saba Kareem <Syed.SabaKareem@amd.com>

Author: saba-kareem

drivers/soundwire/amd_init.c

@@ -120,6 +120,7 @@ static struct sdw_amd_ctx *sdw_amd_probe_controller(struct sdw_amd_res *res)
 
 		sdw_pdata[index].instance = index;
 		sdw_pdata[index].acp_sdw_lock = res->acp_lock;
+		sdw_pdata[index].acp_bra_lock = res->acp_bra_lock;
 		sdw_pdata[index].acp_rev = res->acp_rev;
 		pdevinfo[index].name = "amd_sdw_manager";
 		pdevinfo[index].id = index;