[PATCH v2] ALSA: hda/tas2781: Prevent throwing away custom calibration addresses

[Antheas Kapenekakis <lkml@antheas.dev>]

The V2 UEFI spec for per-device calibration data in TAS allows for
manufacturers to specify up to five custom calibration register
addresses and values to optimize per-device in factory.

A basic description of the spec is found in a comment in function
tas2781_apply_calib(). However, currently, for the condition of
p->dspbin_typ != TASDEV_BASIC, if custom calibration addresses have been
provided by the manufacturer, they are ignored and the ones listed in
firmware are used.

In case the manufacturer chose to change different registers other than
the default ones (r0, invr0, r0_low, pow, tlimit), this causes the
UEFI calibration data to scratch different registers and cause the
firmware to misbehave. This is true in the Xbox ROG Ally X, for one of
the firmwares, where it pops and has audio dropouts after the
calibration data is applied.

Therefore, add a new bool to indicate that UEFI supplied custom
calibration addresses, and if so, use them regardless of dspbin_typ.

Closes: https://lore.kernel.org/all/179122346529.6.9250312386131579603.1671009695@8alias.com/
Co-developed-by: Matthew Schwartz <matthew.schwartz@linux.dev>
Signed-off-by: Matthew Schwartz <matthew.schwartz@linux.dev>
Signed-off-by: Antheas Kapenekakis <lkml@antheas.dev>
---
Different laptop this time. This bug was valid, just not present on the
Xbox Ally X. assembledev is not a real name, so assembledev if you want
a reported by provide a legal name and email address. You may test this
patch and add Tested-by: real-name <real-email> or omit it.

Technically the V1:
https://lore.kernel.org/all/20260107093134.583873-1-lkml@antheas.dev/

No functionality change, just the commit message.
---
 sound/hda/codecs/side-codecs/tas2781_hda.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/sound/hda/codecs/side-codecs/tas2781_hda.c b/sound/hda/codecs/side-codecs/tas2781_hda.c
index e0da299df780..70e5118a17a1 100644
--- a/sound/hda/codecs/side-codecs/tas2781_hda.c
+++ b/sound/hda/codecs/side-codecs/tas2781_hda.c
@@ -64,6 +64,7 @@ static void tas2781_apply_calib(struct tasdevice_priv *p)
 		TASDEVICE_REG(0, 0x18, 0x7c),
 	};
 	unsigned int crc, oft, node_num;
+	bool custom_addr = false;
 	unsigned char *buf;
 	int i, j, k, l;
 
@@ -104,6 +105,7 @@ static void tas2781_apply_calib(struct tasdevice_priv *p)
 		for (j = 0, k = 0; j < node_num; j++) {
 			oft = j * 6 + 3;
 			if (tmp_val[oft] == TASDEV_UEFI_CALI_REG_ADDR_FLG) {
+				custom_addr = true;
 				for (i = 0; i < TASDEV_CALIB_N; i++) {
 					buf = &data[(oft + i + 1) * 4];
 					cali_reg[i] = TASDEVICE_REG(buf[1],
@@ -163,7 +165,7 @@ static void tas2781_apply_calib(struct tasdevice_priv *p)
 		}
 	}
 
-	if (p->dspbin_typ == TASDEV_BASIC) {
+	if (custom_addr || p->dspbin_typ == TASDEV_BASIC) {
 		r->r0_reg = cali_reg[0];
 		r->invr0_reg = cali_reg[1];
 		r->r0_low_reg = cali_reg[2];

base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4
-- 
2.56.0