ASoC: mchp-pdmc: add support for suspend to RAM

Add support for suspend to RAM by re-aranging the lines in switch..case
from mchp_pdmc_trigger() and saving/restoring the enabled interrupts. These
are necessary as AT91 devices has a special power saving mode (called
backup and self-refresh) where most of the SoC parts are powered off
and thus we need to reconfigure the PDMC on resume.
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20221213112851.89212-4-claudiu.beznea@microchip.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/atmel/mchp-pdmc.c

@@ -113,6 +113,7 @@ struct mchp_pdmc {
 	struct clk *pclk;
 	struct clk *gclk;
 	u32 pdmcen;
+	u32 suspend_irq;
 	int mic_no;
 	int sinc_order;
 	bool audio_filter_en;
@@ -641,22 +642,27 @@ static int mchp_pdmc_trigger(struct snd_pcm_substream *substream,
 #endif
 
 	switch (cmd) {
-	case SNDRV_PCM_TRIGGER_START:
 	case SNDRV_PCM_TRIGGER_RESUME:
-	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
+	case SNDRV_PCM_TRIGGER_START:
 		/* Enable overrun and underrun error interrupts */
-		regmap_write(dd->regmap, MCHP_PDMC_IER,
+		regmap_write(dd->regmap, MCHP_PDMC_IER, dd->suspend_irq |
 			     MCHP_PDMC_IR_RXOVR | MCHP_PDMC_IR_RXUDR);
+		dd->suspend_irq = 0;
+		fallthrough;
+	case SNDRV_PCM_TRIGGER_PAUSE_RELEASE:
 		snd_soc_component_update_bits(cpu, MCHP_PDMC_MR,
 					      MCHP_PDMC_MR_PDMCEN_MASK,
 					      dd->pdmcen);
 		break;
-	case SNDRV_PCM_TRIGGER_STOP:
 	case SNDRV_PCM_TRIGGER_SUSPEND:
-	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
+		regmap_read(dd->regmap, MCHP_PDMC_IMR, &dd->suspend_irq);
+		fallthrough;
+	case SNDRV_PCM_TRIGGER_STOP:
 		/* Disable overrun and underrun error interrupts */
-		regmap_write(dd->regmap, MCHP_PDMC_IDR,
+		regmap_write(dd->regmap, MCHP_PDMC_IDR, dd->suspend_irq |
 			     MCHP_PDMC_IR_RXOVR | MCHP_PDMC_IR_RXUDR);
+		fallthrough;
+	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
 		snd_soc_component_update_bits(cpu, MCHP_PDMC_MR,
 					      MCHP_PDMC_MR_PDMCEN_MASK, 0);
 		break;
@@ -1107,6 +1113,7 @@ static const struct of_device_id mchp_pdmc_of_match[] = {
 MODULE_DEVICE_TABLE(of, mchp_pdmc_of_match);
 
 static const struct dev_pm_ops mchp_pdmc_pm_ops = {
+	SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend, pm_runtime_force_resume)
 	RUNTIME_PM_OPS(mchp_pdmc_runtime_suspend, mchp_pdmc_runtime_resume,
 		       NULL)
 };