ASoC: fsl_ssi: mark SACNT register volatile

BugLink: https://bugs.launchpad.net/bugs/1878232

commit 3f1c241f upstream.

SACNT register should be marked volatile since
its WR and RD bits are cleared by SSI after
completing the relevant operation.
This unbreaks AC'97 register access.

Fixes: 05cf2379 ("ASoC: fsl_ssi: Add driver suspend and resume to support MEGA Fast")
Signed-off-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ian May <ian.may@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

sound/soc/fsl/fsl_ssi.c

@@ -146,6 +146,7 @@ static bool fsl_ssi_volatile_reg(struct device *dev, unsigned int reg)
 	case CCSR_SSI_SRX1:
 	case CCSR_SSI_SISR:
 	case CCSR_SSI_SFCSR:
+	case CCSR_SSI_SACNT:
 	case CCSR_SSI_SACADD:
 	case CCSR_SSI_SACDAT:
 	case CCSR_SSI_SATAG:
@@ -239,8 +240,9 @@ struct fsl_ssi_private {
 	unsigned int baudclk_streams;
 	unsigned int bitclk_freq;
 
-	/*regcache for SFCSR*/
+	/* regcache for volatile regs */
 	u32 regcache_sfcsr;
+	u32 regcache_sacnt;
 
 	/* DMA params */
 	struct snd_dmaengine_dai_dma_data dma_params_tx;
@@ -1597,6 +1599,8 @@ static int fsl_ssi_suspend(struct device *dev)
 
 	regmap_read(regs, CCSR_SSI_SFCSR,
 			&ssi_private->regcache_sfcsr);
+	regmap_read(regs, CCSR_SSI_SACNT,
+			&ssi_private->regcache_sacnt);
 
 	regcache_cache_only(regs, true);
 	regcache_mark_dirty(regs);
@@ -1615,6 +1619,8 @@ static int fsl_ssi_resume(struct device *dev)
 			CCSR_SSI_SFCSR_RFWM1_MASK | CCSR_SSI_SFCSR_TFWM1_MASK |
 			CCSR_SSI_SFCSR_RFWM0_MASK | CCSR_SSI_SFCSR_TFWM0_MASK,
 			ssi_private->regcache_sfcsr);
+	regmap_write(regs, CCSR_SSI_SACNT,
+			ssi_private->regcache_sacnt);
 
 	return regcache_sync(regs);
 }