ASoC: mxs-saif: support usage with simple-audio-card

Add support for enabling MCLK output when using the simple-audio-card
driver. In the sound/soc/mxs/mxs-sgtl5000.c use case, that driver
handles MCLK enable/disable by calling mxs_saif_get_mclk() and
mxs_saif_put_mclk() at probe/remove. This does not happen when the
simple-audio-card driver is used. Extend the mxs-saif driver to enable
MCLK output in that scenario.

Co-developed-by: Michael Trimarchi <[e-mail]>
Signed-off-by: Michael Trimarchi <[e-mail]>
Signed-off-by: Dario Binacchi <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

sound/soc/mxs/mxs-saif.c

···
 #define MXS_SET_ADDR	0x4
 #define MXS_CLR_ADDR	0x8
 
+#define MXS_SAIF_BUSY_TIMEOUT_US 10000
+
 static struct mxs_saif *mxs_saif[2];
+
+/*
+ * Since SAIF may work on EXTMASTER mode, IOW, it's working BITCLK&LRCLK
+ * is provided by other SAIF, we provide a interface here to get its master
+ * from its master_id.
+ * Note that the master could be itself.
+ */
+static inline struct mxs_saif *mxs_saif_get_master(struct mxs_saif *saif)
+{
+	return mxs_saif[saif->master_id];
+}
+
+static int __mxs_saif_put_mclk(struct mxs_saif *saif)
+{
+	u32 stat;
+	int ret;
+
+	ret = readx_poll_timeout(__raw_readl, saif->base + SAIF_STAT, stat,
+				 (stat & BM_SAIF_STAT_BUSY) == 0,
+				 MXS_SAIF_BUSY_TIMEOUT_US,
+				 USEC_PER_SEC);
+	if (ret) {
+		dev_err(saif->dev, "error: busy\n");
+		return -EBUSY;
+	}
+
+	/* disable MCLK output */
+	__raw_writel(BM_SAIF_CTRL_CLKGATE,
+		saif->base + SAIF_CTRL + MXS_SET_ADDR);
+	__raw_writel(BM_SAIF_CTRL_RUN,
+		saif->base + SAIF_CTRL + MXS_CLR_ADDR);
+
+	saif->mclk_in_use = 0;
+
+	return 0;
+}
+
+static int __mxs_saif_get_mclk(struct mxs_saif *saif)
+{
+	u32 stat;
+	struct mxs_saif *master_saif;
+
+	if (!saif)
+		return -EINVAL;
+
+	/* Clear Reset */
+	__raw_writel(BM_SAIF_CTRL_SFTRST,
+		saif->base + SAIF_CTRL + MXS_CLR_ADDR);
+
+	/* FIXME: need clear clk gate for register r/w */
+	__raw_writel(BM_SAIF_CTRL_CLKGATE,
+		saif->base + SAIF_CTRL + MXS_CLR_ADDR);
+
+	master_saif = mxs_saif_get_master(saif);
+	if (saif != master_saif) {
+		dev_err(saif->dev, "can not get mclk from a non-master saif\n");
+		return -EINVAL;
+	}
+
+	stat = __raw_readl(saif->base + SAIF_STAT);
+	if (stat & BM_SAIF_STAT_BUSY) {
+		dev_err(saif->dev, "error: busy\n");
+		return -EBUSY;
+	}
+
+	saif->mclk_in_use = 1;
+
+	return 0;
+}
 
 /*
  * SAIF is a little different with other normal SOC DAIs on clock using.
···
 			int clk_id, unsigned int freq, int dir)
 {
 	struct mxs_saif *saif = snd_soc_dai_get_drvdata(cpu_dai);
+	int ret;
 
 	switch (clk_id) {
 	case MXS_SAIF_MCLK:
···
 	default:
 		return -EINVAL;
 	}
-	return 0;
-}
 
-/*
- * Since SAIF may work on EXTMASTER mode, IOW, it's working BITCLK&LRCLK
- * is provided by other SAIF, we provide a interface here to get its master
- * from its master_id.
- * Note that the master could be itself.
- */
-static inline struct mxs_saif *mxs_saif_get_master(struct mxs_saif * saif)
-{
-	return mxs_saif[saif->master_id];
+	if (!saif->mclk_in_use && freq) {
+		ret = __mxs_saif_get_mclk(saif);
+		if (ret)
+			return ret;
+
+		/* enable MCLK output */
+		__raw_writel(BM_SAIF_CTRL_RUN,
+		saif->base + SAIF_CTRL + MXS_SET_ADDR);
+	} else if (saif->mclk_in_use && freq == 0) {
+		ret = __mxs_saif_put_mclk(saif);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
 }
 
 /*
···
 					unsigned int rate)
 {
 	struct mxs_saif *saif = mxs_saif[saif_id];
-	u32 stat;
 	int ret;
-	struct mxs_saif *master_saif;
 
 	if (!saif)
 		return -EINVAL;
 
-	/* Clear Reset */
-	__raw_writel(BM_SAIF_CTRL_SFTRST,
-		saif->base + SAIF_CTRL + MXS_CLR_ADDR);
+	ret = __mxs_saif_get_mclk(saif);
+	if (ret)
+		return ret;
 
-	/* FIXME: need clear clk gate for register r/w */
-	__raw_writel(BM_SAIF_CTRL_CLKGATE,
-		saif->base + SAIF_CTRL + MXS_CLR_ADDR);
-
-	master_saif = mxs_saif_get_master(saif);
-	if (saif != master_saif) {
-		dev_err(saif->dev, "can not get mclk from a non-master saif\n");
-		return -EINVAL;
-	}
-
-	stat = __raw_readl(saif->base + SAIF_STAT);
-	if (stat & BM_SAIF_STAT_BUSY) {
-		dev_err(saif->dev, "error: busy\n");
-		return -EBUSY;
-	}
-
-	saif->mclk_in_use = 1;
 	ret = mxs_saif_set_clk(saif, mclk, rate);
 	if (ret)
 		return ret;