ASoC: cs35l56: Fix illegal writes to OTP_MEM registers

Mark the OTP_MEM registers as volatile so that regcache_sync() will not attempt to write to them.

These registers hold a constant, and originally they were marked as readable non-volatile so that this value would be read into the regmap cache. The problem with this is regcache_sync() issues a write for any cached register that does not have a reg_default.

Though these registers are constants and writing them in normal use cannot change OTP, it is illegal for the host to write to them.

---
 sound/soc/codecs/cs35l56-shared.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

index e05d975ba794..033e56d5e9db 100644
@@ -108,8 +108,6 @@ int cs35l56_set_patch(struct cs35l56_base *cs35l56_base)
 EXPORT_SYMBOL_NS_GPL(cs35l56_set_patch, "SND_SOC_CS35L56_SHARED");
 
 static const struct reg_default cs35l56_reg_defaults[] = {
-	/* no defaults for OTP_MEM - first read populates cache */
-
 	{ CS35L56_ASP1_ENABLES1,		0x00000000 },
 	{ CS35L56_ASP1_CONTROL1,		0x00000028 },
 	{ CS35L56_ASP1_CONTROL2,		0x18180200 },

@@ -138,8 +136,6 @@ static const struct reg_default cs35l56_reg_defaults[] = {
 };
 
 static const struct reg_default cs35l63_reg_defaults[] = {
-	/* no defaults for OTP_MEM - first read populates cache */
-
 	{ CS35L56_ASP1_ENABLES1,		0x00000000 },
 	{ CS35L56_ASP1_CONTROL1,		0x00000028 },
 	{ CS35L56_ASP1_CONTROL2,		0x18180200 },

@@ -282,6 +278,9 @@ static bool cs35l56_common_volatile_reg(unsigned int reg)
 	case CS35L56_GLOBAL_ENABLES:		   /* owned by firmware */
 	case CS35L56_BLOCK_ENABLES:		   /* owned by firmware */
 	case CS35L56_BLOCK_ENABLES2:		   /* owned by firmware */
+	case CS35L56_OTP_MEM_53:
+	case CS35L56_OTP_MEM_54:
+	case CS35L56_OTP_MEM_55:
 	case CS35L56_SYNC_GPIO1_CFG ... CS35L56_ASP2_DIO_GPIO13_CFG:
 	case CS35L56_UPDATE_REGS:
 	case CS35L56_REFCLK_INPUT:		   /* owned by firmware */

2.47.3

This feels like something that's common enough to be worth teaching the regmap core about.

Applied to

https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git for-7.1

Thanks!

[1/1] ASoC: cs35l56: Fix illegal writes to OTP_MEM registers

      https://git.kernel.org/broonie/sound/c/be102efb832e

All being well this means that it will be integrated into the linux-next tree (usually sometime in the next 24 hours) and sent to Linus during the next merge window (or sooner if it is a bug fix), however if problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing and review of the tree, please engage with people reporting problems and send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they should be sent as incremental updates against current git, existing patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying to this mail.

Thanks,
Mark