[alsa-devel] [RFC PATCH 25/40] soundwire: intel: use BIOS information to set clock dividers

[Pierre-Louis Bossart]

The BIOS provides an Intel-specific property, let's use it to avoid
hard-coded clock dividers.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
---
 drivers/soundwire/cadence_master.c | 26 ++++++++++++++++++++++----
 drivers/soundwire/intel.c          | 26 ++++++++++++++++++++++++++
 include/linux/soundwire/sdw.h      |  2 ++
 3 files changed, 50 insertions(+), 4 deletions(-)

diff --git a/drivers/soundwire/cadence_master.c b/drivers/soundwire/cadence_master.c
index d84344e29f71..10ebcef2e84e 100644
--- a/drivers/soundwire/cadence_master.c
+++ b/drivers/soundwire/cadence_master.c
@@ -173,8 +173,6 @@
 #define CDNS_PDI_CONFIG_PORT			GENMASK(4, 0)
 
 /* Driver defaults */
-
-#define CDNS_DEFAULT_CLK_DIVIDER		0
 #define CDNS_DEFAULT_SSP_INTERVAL		0x18
 #define CDNS_TX_TIMEOUT				2000
 
@@ -973,7 +971,10 @@ static u32 cdns_set_default_frame_shape(int n_rows, int n_cols)
  */
 int sdw_cdns_init(struct sdw_cdns *cdns)
 {
+	struct sdw_bus *bus = &cdns->bus;
+	struct sdw_master_prop *prop = &bus->prop;
 	u32 val;
+	int divider;
 	int ret;
 
 	/* Exit clock stop */
@@ -985,9 +986,17 @@ int sdw_cdns_init(struct sdw_cdns *cdns)
 	}
 
 	/* Set clock divider */
+	divider	= (prop->mclk_freq / prop->max_clk_freq) - 1;
 	val = cdns_readl(cdns, CDNS_MCP_CLK_CTRL0);
-	val |= CDNS_DEFAULT_CLK_DIVIDER;
+	val |= divider;
 	cdns_writel(cdns, CDNS_MCP_CLK_CTRL0, val);
+	cdns_writel(cdns, CDNS_MCP_CLK_CTRL1, val);
+
+	pr_err("plb: mclk %d max_freq %d divider %d register %x\n",
+	       prop->mclk_freq,
+	       prop->max_clk_freq,
+	       divider,
+	       val);
 
 	/* Set the default frame shape */
 	val = cdns_set_default_frame_shape(prop->default_row,
@@ -1035,6 +1044,7 @@ EXPORT_SYMBOL(sdw_cdns_init);
 
 int cdns_bus_conf(struct sdw_bus *bus, struct sdw_bus_params *params)
 {
+	struct sdw_master_prop *prop = &bus->prop;
 	struct sdw_cdns *cdns = bus_to_cdns(bus);
 	int mcp_clkctrl_off, mcp_clkctrl;
 	int divider;
@@ -1044,7 +1054,9 @@ int cdns_bus_conf(struct sdw_bus *bus, struct sdw_bus_params *params)
 		return -EINVAL;
 	}
 
-	divider	= (params->max_dr_freq / params->curr_dr_freq) - 1;
+	divider	= prop->mclk_freq * SDW_DOUBLE_RATE_FACTOR /
+		params->curr_dr_freq;
+	divider--; /* divider is 1/(N+1) */
 
 	if (params->next_bank)
 		mcp_clkctrl_off = CDNS_MCP_CLK_CTRL1;
@@ -1055,6 +1067,12 @@ int cdns_bus_conf(struct sdw_bus *bus, struct sdw_bus_params *params)
 	mcp_clkctrl |= divider;
 	cdns_writel(cdns, mcp_clkctrl_off, mcp_clkctrl);
 
+	pr_err("plb: mclk * 2 %d curr_dr_freq %d divider %d register %x\n",
+	       prop->mclk_freq * SDW_DOUBLE_RATE_FACTOR,
+	       params->curr_dr_freq,
+	       divider,
+	       mcp_clkctrl);
+
 	return 0;
 }
 EXPORT_SYMBOL(cdns_bus_conf);
diff --git a/drivers/soundwire/intel.c b/drivers/soundwire/intel.c
index c718c9c67a37..796ac2bc8cea 100644
--- a/drivers/soundwire/intel.c
+++ b/drivers/soundwire/intel.c
@@ -917,11 +917,37 @@ static int intel_register_dai(struct sdw_intel *sdw)
 					  dais, num_dai);
 }
 
+static int sdw_master_read_intel_prop(struct sdw_bus *bus)
+{
+	struct sdw_master_prop *prop = &bus->prop;
+	struct fwnode_handle *link;
+	char name[32];
+	int nval, i;
+
+	/* Find master handle */
+	snprintf(name, sizeof(name),
+		 "mipi-sdw-link-%d-subproperties", bus->link_id);
+
+	link = device_get_named_child_node(bus->dev, name);
+	if (!link) {
+		dev_err(bus->dev, "Master node %s not found\n", name);
+		return -EIO;
+	}
+
+	fwnode_property_read_u32(link,
+				 "intel-sdw-ip-clock",
+				 &prop->mclk_freq);
+	return 0;
+}
+
 static int intel_prop_read(struct sdw_bus *bus)
 {
 	/* Initialize with default handler to read all DisCo properties */
 	sdw_master_read_prop(bus);
 
+	/* read Intel-specific properties */
+	sdw_master_read_intel_prop(bus);
+
 	return 0;
 }
 
diff --git a/include/linux/soundwire/sdw.h b/include/linux/soundwire/sdw.h
index 31d1e8acf25b..b6acc436ac80 100644
--- a/include/linux/soundwire/sdw.h
+++ b/include/linux/soundwire/sdw.h
@@ -379,6 +379,7 @@ struct sdw_slave_prop {
  * @dynamic_frame: Dynamic frame shape supported
  * @err_threshold: Number of times that software may retry sending a single
  * command
+ * @mclk_freq: clock reference passed to SoundWire Master, in Hz.
  */
 struct sdw_master_prop {
 	u32 revision;
@@ -393,6 +394,7 @@ struct sdw_master_prop {
 	u32 default_col;
 	bool dynamic_frame;
 	u32 err_threshold;
+	u32 mclk_freq;
 };
 
 int sdw_master_read_prop(struct sdw_bus *bus);
-- 
2.20.1