ASoC: cs42l42: PLL must be running when changing MCLK_SRC_SEL

Both SCLK and PLL clocks must be running to drive the glitch-free mux
behind MCLK_SRC_SEL and complete the switchover.

This patch moves the writing of MCLK_SRC_SEL to when the PLL is started
and stopped, so that it only transitions while the PLL is running.
The unconditional write MCLK_SRC_SEL=0 in cs42l42_mute_stream() is safe
because if the PLL is not running MCLK_SRC_SEL is already 0.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Fixes: 43fc357 ("ASoC: cs42l42: Set clock source for both ways of stream")
Link: https://lore.kernel.org/r/20210805161111.10410-1-rf@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/cs42l42.c

@@ -619,6 +619,8 @@ static int cs42l42_pll_config(struct snd_soc_component *component)
 
 	for (i = 0; i < ARRAY_SIZE(pll_ratio_table); i++) {
 		if (pll_ratio_table[i].sclk == clk) {
+			cs42l42->pll_config = i;
+
 			/* Configure the internal sample rate */
 			snd_soc_component_update_bits(component, CS42L42_MCLK_CTL,
 					CS42L42_INTERNAL_FS_MASK,
@@ -627,14 +629,9 @@ static int cs42l42_pll_config(struct snd_soc_component *component)
 					(pll_ratio_table[i].mclk_int !=
 					24000000)) <<
 					CS42L42_INTERNAL_FS_SHIFT);
-			/* Set the MCLK src (PLL or SCLK) and the divide
-			 * ratio
-			 */
+
 			snd_soc_component_update_bits(component, CS42L42_MCLK_SRC_SEL,
-					CS42L42_MCLK_SRC_SEL_MASK |
 					CS42L42_MCLKDIV_MASK,
-					(pll_ratio_table[i].mclk_src_sel
-					<< CS42L42_MCLK_SRC_SEL_SHIFT) |
 					(pll_ratio_table[i].mclk_div <<
 					CS42L42_MCLKDIV_SHIFT));
 			/* Set up the LRCLK */
@@ -892,13 +889,21 @@ static int cs42l42_mute_stream(struct snd_soc_dai *dai, int mute, int stream)
 			 */
 			regmap_multi_reg_write(cs42l42->regmap, cs42l42_to_osc_seq,
 					       ARRAY_SIZE(cs42l42_to_osc_seq));
+
+			/* Must disconnect PLL before stopping it */
+			snd_soc_component_update_bits(component,
+						      CS42L42_MCLK_SRC_SEL,
+						      CS42L42_MCLK_SRC_SEL_MASK,
+						      0);
+			usleep_range(100, 200);
+
 			snd_soc_component_update_bits(component, CS42L42_PLL_CTL1,
 						      CS42L42_PLL_START_MASK, 0);
 		}
 	} else {
 		if (!cs42l42->stream_use) {
 			/* SCLK must be running before codec unmute */
-			if ((cs42l42->bclk < 11289600) && (cs42l42->sclk < 11289600)) {
+			if (pll_ratio_table[cs42l42->pll_config].mclk_src_sel) {
 				snd_soc_component_update_bits(component, CS42L42_PLL_CTL1,
 							      CS42L42_PLL_START_MASK, 1);
 
@@ -919,6 +924,12 @@ static int cs42l42_mute_stream(struct snd_soc_dai *dai, int mute, int stream)
 							       CS42L42_PLL_LOCK_TIMEOUT_US);
 				if (ret < 0)
 					dev_warn(component->dev, "PLL failed to lock: %d\n", ret);
+
+				/* PLL must be running to drive glitchless switch logic */
+				snd_soc_component_update_bits(component,
+							      CS42L42_MCLK_SRC_SEL,
+							      CS42L42_MCLK_SRC_SEL_MASK,
+							      CS42L42_MCLK_SRC_SEL_MASK);
 			}
 
 			/* Mark SCLK as present, turn off internal oscillator */

sound/soc/codecs/cs42l42.h

@@ -775,6 +775,7 @@ struct  cs42l42_private {
 	struct gpio_desc *reset_gpio;
 	struct completion pdn_done;
 	struct snd_soc_jack *jack;
+	int pll_config;
 	int bclk;
 	u32 sclk;
 	u32 srate;