ASoC: SOF: imx8m: Implement DSP start

On i.MX8M DSP is controlled via a set of registers
from Audio MIX. This patches gets a reference (via regmap)
to Audio Mix registers and implements DSP start.
Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20211119094319.81674-5-daniel.baluta@oss.nxp.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/imx/imx8m.c

@@ -6,10 +6,13 @@
 //
 // Hardware interface for audio DSP on i.MX8M
 
+#include <linux/bits.h>
 #include <linux/firmware.h>
+#include <linux/mfd/syscon.h>
 #include <linux/of_platform.h>
 #include <linux/of_address.h>
 #include <linux/of_irq.h>
+#include <linux/regmap.h>
 
 #include <linux/module.h>
 #include <sound/sof.h>
@@ -29,6 +32,14 @@ static struct clk_bulk_data imx8m_dsp_clks[] = {
 	{ .id = "core" },
 };
 
+/* DSP audio mix registers */
+#define AudioDSP_REG0	0x100
+#define AudioDSP_REG1	0x104
+#define AudioDSP_REG2	0x108
+#define AudioDSP_REG3	0x10c
+
+#define AudioDSP_REG2_RUNSTALL	BIT(5)
+
 struct imx8m_priv {
 	struct device *dev;
 	struct snd_sof_dev *sdev;
@@ -38,6 +49,8 @@ struct imx8m_priv {
 	struct platform_device *ipc_dev;
 
 	struct imx_clocks *clks;
+
+	struct regmap *regmap;
 };
 
 static int imx8m_get_mailbox_offset(struct snd_sof_dev *sdev)
@@ -96,7 +109,10 @@ static int imx8m_send_msg(struct snd_sof_dev *sdev, struct snd_sof_ipc_msg *msg)
  */
 static int imx8m_run(struct snd_sof_dev *sdev)
 {
-	/* TODO: start DSP using Audio MIX bits */
+	struct imx8m_priv *priv = (struct imx8m_priv *)sdev->pdata->hw_pdata;
+
+	regmap_update_bits(priv->regmap, AudioDSP_REG2, AudioDSP_REG2_RUNSTALL, 0);
+
 	return 0;
 }
 
@@ -187,6 +203,13 @@ static int imx8m_probe(struct snd_sof_dev *sdev)
 	/* set default mailbox offset for FW ready message */
 	sdev->dsp_box.offset = MBOX_OFFSET;
 
+	priv->regmap = syscon_regmap_lookup_by_compatible("fsl,dsp-ctrl");
+	if (IS_ERR(priv->regmap)) {
+		dev_err(sdev->dev, "cannot find dsp-ctrl registers");
+		ret = PTR_ERR(priv->regmap);
+		goto exit_pdev_unregister;
+	}
+
 	/* init clocks info */
 	priv->clks->dsp_clks = imx8m_dsp_clks;
 	priv->clks->num_dsp_clks = ARRAY_SIZE(imx8m_dsp_clks);