[PATCH 4/4] soundwire: bus: initialize bus clock base and scale registers

[Bard Liao]

From: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>

The SoundWire 1.2 specification adds new registers to allow for
seamless clock changes while audio transfers are on-going. Program
them following the specification.

Note that dynamic clock changes are not supported for now, this only
adds the register initialization.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>
Reviewed-by: Kai Vehmanen <kai.vehmanen@xxxxxxxxxxxxxxx>
Reviewed-by: Guennadi Liakhovetski <guennadi.liakhovetski@xxxxxxxxxxxxxxx>
Signed-off-by: Bard Liao <yung-chuan.liao@xxxxxxxxxxxxxxx>
---
 drivers/soundwire/bus.c                 | 107 ++++++++++++++++++++++++
 include/linux/soundwire/sdw_registers.h |  10 +++
 2 files changed, 117 insertions(+)

diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
index 24ba77226376..83f9d7e0de80 100644
--- a/drivers/soundwire/bus.c
+++ b/drivers/soundwire/bus.c
@@ -1059,12 +1059,119 @@ int sdw_configure_dpn_intr(struct sdw_slave *slave,
 	return ret;
 }
 
+static int sdw_slave_set_frequency(struct sdw_slave *slave)
+{
+	u32 mclk_freq = slave->bus->prop.mclk_freq;
+	u32 curr_freq = slave->bus->params.curr_dr_freq >> 1;
+	unsigned int scale;
+	u8 scale_index;
+	u8 base;
+	int ret;
+
+	/*
+	 * frequency base and scale registers are required for SDCA
+	 * devices. They may also be used for 1.2+/non-SDCA devices,
+	 * but we will need a DisCo property to cover this case
+	 */
+	if (!slave->id.class_id)
+		return 0;
+
+	if (!mclk_freq) {
+		dev_err(&slave->dev,
+			"no bus MCLK, cannot set SDW_SCP_BUS_CLOCK_BASE\n");
+		return -EINVAL;
+	}
+
+	/*
+	 * map base frequency using Table 89 of SoundWire 1.2 spec.
+	 * The order of the tests just follows the specification, this
+	 * is not a selection between possible values or a search for
+	 * the best value but just a mapping.  Only one case per platform
+	 * is relevant.
+	 * Some BIOS have inconsistent values for mclk_freq but a
+	 * correct root so we force the mclk_freq to avoid variations.
+	 */
+	if (!(19200000 % mclk_freq)) {
+		mclk_freq = 19200000;
+		base = SDW_SCP_BASE_CLOCK_19200000_HZ;
+	} else if (!(24000000 % mclk_freq)) {
+		mclk_freq = 24000000;
+		base = SDW_SCP_BASE_CLOCK_24000000_HZ;
+	} else if (!(24576000 % mclk_freq)) {
+		mclk_freq = 24576000;
+		base = SDW_SCP_BASE_CLOCK_24576000_HZ;
+	} else if (!(22579200 % mclk_freq)) {
+		mclk_freq = 22579200;
+		base = SDW_SCP_BASE_CLOCK_22579200_HZ;
+	} else if (!(32000000 % mclk_freq)) {
+		mclk_freq = 32000000;
+		base = SDW_SCP_BASE_CLOCK_32000000_HZ;
+	} else {
+		dev_err(&slave->dev,
+			"Unsupported clock base, mclk %d\n",
+			mclk_freq);
+		return -EINVAL;
+	}
+
+	if (mclk_freq % curr_freq) {
+		dev_err(&slave->dev,
+			"mclk %d is not multiple of bus curr_freq %d\n",
+			mclk_freq, curr_freq);
+		return -EINVAL;
+	}
+
+	scale = mclk_freq / curr_freq;
+
+	/*
+	 * map scale to Table 90 of SoundWire 1.2 spec - and check
+	 * that the scale is a power of two and maximum 64
+	 */
+	scale_index = ilog2(scale);
+
+	if (BIT(scale_index) != scale || scale_index > 6) {
+		dev_err(&slave->dev,
+			"No match found for scale %d, bus mclk %d curr_freq %d\n",
+			scale, mclk_freq, curr_freq);
+		return -EINVAL;
+	}
+	scale_index++;
+
+	ret = sdw_write(slave, SDW_SCP_BUS_CLOCK_BASE, base);
+	if (ret < 0) {
+		dev_err(&slave->dev,
+			"SDW_SCP_BUS_CLOCK_BASE write failed:%d\n", ret);
+		return ret;
+	}
+
+	/* initialize scale for both banks */
+	ret = sdw_write(slave, SDW_SCP_BUSCLOCK_SCALE_B0, scale_index);
+	if (ret < 0) {
+		dev_err(&slave->dev,
+			"SDW_SCP_BUSCLOCK_SCALE_B0 write failed:%d\n", ret);
+		return ret;
+	}
+	ret = sdw_write(slave, SDW_SCP_BUSCLOCK_SCALE_B1, scale_index);
+	if (ret < 0)
+		dev_err(&slave->dev,
+			"SDW_SCP_BUSCLOCK_SCALE_B1 write failed:%d\n", ret);
+
+	dev_dbg(&slave->dev,
+		"Configured bus base %d, scale %d, mclk %d, curr_freq %d\n",
+		base, scale_index, mclk_freq, curr_freq);
+
+	return ret;
+}
+
 static int sdw_initialize_slave(struct sdw_slave *slave)
 {
 	struct sdw_slave_prop *prop = &slave->prop;
 	int ret;
 	u8 val;
 
+	ret = sdw_slave_set_frequency(slave);
+	if (ret < 0)
+		return ret;
+
 	/*
 	 * Set bus clash, parity and SCP implementation
 	 * defined interrupt mask
diff --git a/include/linux/soundwire/sdw_registers.h b/include/linux/soundwire/sdw_registers.h
index 12f9ffc3eb3b..5d3c271af7d1 100644
--- a/include/linux/soundwire/sdw_registers.h
+++ b/include/linux/soundwire/sdw_registers.h
@@ -109,8 +109,18 @@
 #define SDW_SCP_KEEPEREN			0x4A
 #define SDW_SCP_BANKDELAY			0x4B
 #define SDW_SCP_COMMIT				0x4C
+
 #define SDW_SCP_BUS_CLOCK_BASE			0x4D
 #define SDW_SCP_BASE_CLOCK_FREQ			GENMASK(2, 0)
+#define SDW_SCP_BASE_CLOCK_UNKNOWN		0x0
+#define SDW_SCP_BASE_CLOCK_19200000_HZ		0x1
+#define SDW_SCP_BASE_CLOCK_24000000_HZ		0x2
+#define SDW_SCP_BASE_CLOCK_24576000_HZ		0x3
+#define SDW_SCP_BASE_CLOCK_22579200_HZ		0x4
+#define SDW_SCP_BASE_CLOCK_32000000_HZ		0x5
+#define SDW_SCP_BASE_CLOCK_RESERVED		0x6
+#define SDW_SCP_BASE_CLOCK_IMP_DEF		0x7
+
 /* 0x4E is not allocated in SoundWire specification 1.2 */
 #define SDW_SCP_TESTMODE			0x4F
 #define SDW_SCP_DEVID_0				0x50
-- 
2.17.1