sst: avoid unnecessary firmware reloading for MRST

SST HW on MRST doesn't need to reload the firmware during suspend/resume
cycle, so remove the extra workload. This also fix a bug that the firmware
sample rate can't be modified when there is no active playback/capture
stream.
Signed-off-by: Feng Tang <feng.tang@intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/intel_sst/intel_sst.c

@@ -545,7 +545,10 @@ static int intel_sst_runtime_suspend(struct device *dev)
 	/* Move the SST state to Suspended */
 	mutex_lock(&sst_drv_ctx->sst_lock);
 	sst_drv_ctx->sst_state = SST_SUSPENDED;
-	sst_shim_write(sst_drv_ctx->shim, SST_CSR, csr.full);
+
+	/* Only needed by Medfield */
+	if (sst_drv_ctx->pci_id != SST_MRST_PCI_ID)
+		sst_shim_write(sst_drv_ctx->shim, SST_CSR, csr.full);
 	mutex_unlock(&sst_drv_ctx->sst_lock);
 	return 0;
 }

drivers/staging/intel_sst/intel_sst_common.h

@@ -420,6 +420,8 @@ struct intel_sst_drv {
 	unsigned int		max_streams;
 	unsigned int		*fw_cntx;
 	unsigned int		fw_cntx_size;
+
+	unsigned int		fw_downloaded;
 };
 
 extern struct intel_sst_drv *sst_drv_ctx;

drivers/staging/intel_sst/intel_sst_drv_interface.c

@@ -53,6 +53,13 @@ int sst_download_fw(void)
 	if (sst_drv_ctx->sst_state != SST_UN_INIT)
 		return -EPERM;
 
+	/* Reload firmware is not needed for MRST */
+	if ( (sst_drv_ctx->pci_id == SST_MRST_PCI_ID) && sst_drv_ctx->fw_downloaded) {
+		pr_debug("FW already downloaded, skip for MRST platform\n");
+		sst_drv_ctx->sst_state = SST_FW_RUNNING;
+		return 0;
+	}
+
 	snprintf(name, sizeof(name), "%s%04x%s", "fw_sst_",
 					sst_drv_ctx->pci_id, ".bin");
 
@@ -71,6 +78,9 @@ int sst_download_fw(void)
 	retval = sst_wait_timeout(sst_drv_ctx, &sst_drv_ctx->alloc_block[0]);
 	if (retval)
 		pr_err("fw download failed %d\n" , retval);
+	else
+		sst_drv_ctx->fw_downloaded = 1;
+
 end_restore:
 	release_firmware(fw_sst);
 	sst_drv_ctx->alloc_block[0].sst_id = BLOCK_UNINIT;