ASoC: cs35l56: Prevent overwriting firmware ASP config

Only populate the ASP1 config registers in the regmap cache if the
ASP DAI is used. This prevents regcache_sync() from overwriting
these registers with their defaults when the firmware owns
control of these registers.

On a SoundWire system the ASP could be owned by the firmware to
share reference audio with the firmware on other cs35l56. Or it
can be used as a normal codec-codec interface owned by the driver.
The driver must not overwrite the registers if the firmware has
control of them.

The original implementation for this in commit 07f7d6e7a124
("ASoC: cs35l56: Fix for initializing ASP1 mixer registers") was
to still provide defaults for these registers, assuming that if
they were never reconfigured from defaults then regcache_sync()
would not write them out because they are not dirty. Unfortunately
regcache_sync() is not that smart. If the chip has not reset (so
the driver has not called regcache_mark_dirty()) a regcache_sync()
could write out registers that are not dirty.

To avoid accidental overwriting of the ASP registers, they are
removed from the table of defaults and instead are populated with
defaults only if one of the ASP DAI configuration functions is
called. So if the DAI has never been configured, the firmware is
assumed to have ownership of these registers, and the regmap cache
will not contain any entries for them.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Fixes: 07f7d6e7a124 ("ASoC: cs35l56: Fix for initializing ASP1 mixer registers")
Link: https://msgid.link/r/20240408101803.43183-5-rf@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 23 insertions, 1 deletions

diff --git a/sound/soc/codecs/cs35l56.c b/sound/soc/codecs/cs35l56.c
index 5a4e0e479414..6331b8c6136e 100644
--- a/sound/soc/codecs/cs35l56.c
+++ b/sound/soc/codecs/cs35l56.c
@@ -454,9 +454,14 @@ static int cs35l56_asp_dai_set_fmt(struct snd_soc_dai *codec_dai, unsigned int f
 {
 	struct cs35l56_private *cs35l56 = snd_soc_component_get_drvdata(codec_dai->component);
 	unsigned int val;
+	int ret;
 
 	dev_dbg(cs35l56->base.dev, "%s: %#x\n", __func__, fmt);
 
+	ret = cs35l56_init_asp1_regs_for_driver_control(&cs35l56->base);
+	if (ret)
+		return ret;
+
 	switch (fmt & SND_SOC_DAIFMT_CLOCK_PROVIDER_MASK) {
 	case SND_SOC_DAIFMT_CBC_CFC:
 		break;
@@ -530,6 +535,11 @@ static int cs35l56_asp_dai_set_tdm_slot(struct snd_soc_dai *dai, unsigned int tx
 					unsigned int rx_mask, int slots, int slot_width)
 {
 	struct cs35l56_private *cs35l56 = snd_soc_component_get_drvdata(dai->component);
+	int ret;
+
+	ret = cs35l56_init_asp1_regs_for_driver_control(&cs35l56->base);
+	if (ret)
+		return ret;
 
 	if ((slots == 0) || (slot_width == 0)) {
 		dev_dbg(cs35l56->base.dev, "tdm config cleared\n");
@@ -578,6 +588,11 @@ static int cs35l56_asp_dai_hw_params(struct snd_pcm_substream *substream,
 	struct cs35l56_private *cs35l56 = snd_soc_component_get_drvdata(dai->component);
 	unsigned int rate = params_rate(params);
 	u8 asp_width, asp_wl;
+	int ret;
+
+	ret = cs35l56_init_asp1_regs_for_driver_control(&cs35l56->base);
+	if (ret)
+		return ret;
 
 	asp_wl = params_width(params);
 	if (cs35l56->asp_slot_width)
@@ -634,7 +649,11 @@ static int cs35l56_asp_dai_set_sysclk(struct snd_soc_dai *dai,
 				      int clk_id, unsigned int freq, int dir)
 {
 	struct cs35l56_private *cs35l56 = snd_soc_component_get_drvdata(dai->component);
-	int freq_id;
+	int freq_id, ret;
+
+	ret = cs35l56_init_asp1_regs_for_driver_control(&cs35l56->base);
+	if (ret)
+		return ret;
 
 	if (freq == 0) {
 		cs35l56->sysclk_set = false;
@@ -1403,6 +1422,9 @@ int cs35l56_common_probe(struct cs35l56_private *cs35l56)
 	cs35l56->base.cal_index = -1;
 	cs35l56->speaker_id = -ENOENT;
 
+	/* Assume that the firmware owns ASP1 until we know different */
+	cs35l56->base.fw_owns_asp1 = true;
+
 	dev_set_drvdata(cs35l56->base.dev, cs35l56);
 
 	cs35l56_fill_supply_names(cs35l56->supplies);