ASoC: fsl_sai: Add support for PLL switch at runtime

i.MX8MQ/MN/MM/MP platforms typically have 2 AUDIO PLLs being
configured to handle 8kHz and 11kHz series audio rates.

The patch implements the functionality to select at runtime
the appropriate AUDIO PLL as function of sysclk rate.

Signed-off-by: Viorel Suman <[e-mail]>
Signed-off-by: Shengjiu Wang <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

sound/soc/fsl/Kconfig

···
 	select REGMAP_MMIO
 	select SND_SOC_IMX_PCM_DMA if SND_IMX_SOC != n
 	select SND_SOC_GENERIC_DMAENGINE_PCM
+	select SND_SOC_FSL_UTILS
 	help
 	  Say Y if you want to add Synchronous Audio Interface (SAI)
 	  support for the Freescale CPUs.

sound/soc/fsl/fsl_sai.c

···
 #include <linux/mfd/syscon/imx6q-iomuxc-gpr.h>
 
 #include "fsl_sai.h"
+#include "fsl_utils.h"
 #include "imx-pcm.h"
 
 #define FSL_SAI_FLAGS (FSL_SAI_CSR_SEIE |\
···
 	return 0;
 }
 
+static int fsl_sai_set_mclk_rate(struct snd_soc_dai *dai, int clk_id, unsigned int freq)
+{
+	struct fsl_sai *sai = snd_soc_dai_get_drvdata(dai);
+	int ret;
+
+	fsl_asoc_reparent_pll_clocks(dai->dev, sai->mclk_clk[clk_id],
+				     sai->pll8k_clk, sai->pll11k_clk, freq);
+
+	ret = clk_set_rate(sai->mclk_clk[clk_id], freq);
+	if (ret < 0)
+		dev_err(dai->dev, "failed to set clock rate (%u): %d\n", freq, ret);
+
+	return ret;
+}
+
 static int fsl_sai_set_dai_sysclk(struct snd_soc_dai *cpu_dai,
 		int clk_id, unsigned int freq, int dir)
 {
+	struct fsl_sai *sai = snd_soc_dai_get_drvdata(cpu_dai);
 	int ret;
 
 	if (dir == SND_SOC_CLOCK_IN)
 		return 0;
+
+	if (freq > 0 && clk_id != FSL_SAI_CLK_BUS) {
+		if (clk_id < 0 || clk_id >= FSL_SAI_MCLK_MAX) {
+			dev_err(cpu_dai->dev, "Unknown clock id: %d\n", clk_id);
+			return -EINVAL;
+		}
+
+		if (IS_ERR_OR_NULL(sai->mclk_clk[clk_id])) {
+			dev_err(cpu_dai->dev, "Unassigned clock: %d\n", clk_id);
+			return -EINVAL;
+		}
+
+		if (sai->mclk_streams == 0) {
+			ret = fsl_sai_set_mclk_rate(cpu_dai, clk_id, freq);
+			if (ret < 0)
+				return ret;
+		}
+	}
 
 	ret = fsl_sai_set_dai_sysclk_tr(cpu_dai, clk_id, freq, true);
 	if (ret) {
···
 		sai->mclk_clk[0] = sai->mclk_clk[1];
 	else
 		sai->mclk_clk[0] = sai->bus_clk;
+
+	fsl_asoc_get_pll_clocks(&pdev->dev, &sai->pll8k_clk,
+				&sai->pll11k_clk);
 
 	/* read dataline mask for rx and tx*/
 	ret = fsl_sai_read_dlcfg(sai);

sound/soc/fsl/fsl_sai.h

···
 	struct regmap *regmap;
 	struct clk *bus_clk;
 	struct clk *mclk_clk[FSL_SAI_MCLK_MAX];
+	struct clk *pll8k_clk;
+	struct clk *pll11k_clk;
 	struct resource *res;
 
 	bool is_consumer_mode;