ASoC: fsl_sai: Refine regcache usage with pm runtime

When there is dedicated power domain bound with device, after probing
the power will be disabled, then registers are not accessible in
fsl_sai_dai_probe(), so regcache only need to be enabled in end of
probe() and regcache_mark_dirty should be moved to pm runtime resume
callback function.

Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Acked-by: Nicolin Chen <nicoleotsuka@gmail.com>
Link: https://lore.kernel.org/r/1593412953-10897-1-git-send-email-shengjiu.wang@nxp.com
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/fsl/fsl_sai.c

@@ -1016,6 +1016,7 @@ static int fsl_sai_probe(struct platform_device *pdev)
 	platform_set_drvdata(pdev, sai);
 
 	pm_runtime_enable(&pdev->dev);
+	regcache_cache_only(sai->regmap, true);
 
 	ret = devm_snd_soc_register_component(&pdev->dev, &fsl_component,
 			&fsl_sai_dai, 1);
@@ -1107,7 +1108,6 @@ static int fsl_sai_runtime_suspend(struct device *dev)
 	clk_disable_unprepare(sai->bus_clk);
 
 	regcache_cache_only(sai->regmap, true);
-	regcache_mark_dirty(sai->regmap);
 
 	return 0;
 }
@@ -1137,6 +1137,7 @@ static int fsl_sai_runtime_resume(struct device *dev)
 	}
 
 	regcache_cache_only(sai->regmap, false);
+	regcache_mark_dirty(sai->regmap);
 	regmap_write(sai->regmap, FSL_SAI_TCSR(ofs), FSL_SAI_CSR_SR);
 	regmap_write(sai->regmap, FSL_SAI_RCSR(ofs), FSL_SAI_CSR_SR);
 	usleep_range(1000, 2000);