ALSA: hda/cs35l56: Do not download firmware over existing RAM firmware

A RAM firmware can only be downloaded if the CS35L56 is currently
running from ROM firmware. The driver must not try to overwrite
the RAM if the CS35L56 is already running from that RAM.

Firmware can be downloaded in these two cases:

- The BIOS has already patched the firmware (secured mode).
  In this case the firmware files will only contain tunings that
  are safe to overwrite.

- The CS35L56 is running the built-in ROM firmware.

After a RAM firmware has been downloaded it can only be cleared by
hard resetting CS35L56. Some systems only hard-reset during
power-on and do not give the driver control of hard reset.
Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20230731165726.7940-8-rf@opensource.cirrus.comSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/hda/cs35l56_hda.c

@@ -525,6 +525,7 @@ static int cs35l56_hda_fw_load(struct cs35l56_hda *cs35l56)
 	const struct firmware *wmfw_firmware = NULL;
 	char *coeff_filename = NULL;
 	char *wmfw_filename = NULL;
+	unsigned int firmware_missing;
 	int ret = 0;
 
 	/* Prepare for a new DSP power-up */
@@ -533,11 +534,28 @@ static int cs35l56_hda_fw_load(struct cs35l56_hda *cs35l56)
 
 	cs35l56->base.fw_patched = false;
 
-	cs35l56_hda_request_firmware_files(cs35l56, &wmfw_firmware, &wmfw_filename,
-					   &coeff_firmware, &coeff_filename);
+	pm_runtime_get_sync(cs35l56->base.dev);
+
+	ret = regmap_read(cs35l56->base.regmap, CS35L56_PROTECTION_STATUS, &firmware_missing);
+	if (ret) {
+		dev_err(cs35l56->base.dev, "Failed to read PROTECTION_STATUS: %d\n", ret);
+		goto err_pm_put;
+	}
+
+	firmware_missing &= CS35L56_FIRMWARE_MISSING;
+
+	/*
+	 * Firmware can only be downloaded if the CS35L56 is secured or is
+	 * running from the built-in ROM. If it is secured the BIOS will have
+	 * downloaded firmware, and the wmfw/bin files will only contain
+	 * tunings that are safe to download with the firmware running.
+	 */
+	if (cs35l56->base.secured || firmware_missing) {
+		cs35l56_hda_request_firmware_files(cs35l56, &wmfw_firmware, &wmfw_filename,
+						   &coeff_firmware, &coeff_filename);
+	}
 
 	mutex_lock(&cs35l56->base.irq_lock);
-	pm_runtime_get_sync(cs35l56->base.dev);
 
 	/*
 	 * When the device is running in secure mode the firmware files can
@@ -596,11 +614,12 @@ static int cs35l56_hda_fw_load(struct cs35l56_hda *cs35l56)
 	if (!cs35l56->base.fw_patched)
 		cs_dsp_power_down(&cs35l56->cs_dsp);
 err:
-	pm_runtime_put(cs35l56->base.dev);
 	mutex_unlock(&cs35l56->base.irq_lock);
 
 	cs35l56_hda_release_firmware_files(wmfw_firmware, wmfw_filename,
 					   coeff_firmware, coeff_filename);
+err_pm_put:
+	pm_runtime_put(cs35l56->base.dev);
 
 	return ret;
 }