Re: [alsa-devel] [RESEND PATCH v4 2/4] soundwire: core: add device tree support for slave devices

[Pierre-Louis Bossart]

On 8/22/19 6:37 PM, Srinivas Kandagatla wrote:
This patch adds support to parsing device tree based
SoundWire slave devices.

Signed-off-by: Srinivas Kandagatla <srinivas.kandaga...@linaro.org>
---
  drivers/soundwire/bus.c   |  2 ++
  drivers/soundwire/bus.h   |  1 +
  drivers/soundwire/slave.c | 52 +++++++++++++++++++++++++++++++++++++++
  3 files changed, 55 insertions(+)

diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
index 49f64b2115b9..c2eaeb5c38ed 100644
--- a/drivers/soundwire/bus.c
+++ b/drivers/soundwire/bus.c
@@ -77,6 +77,8 @@ int sdw_add_bus_master(struct sdw_bus *bus)
         */
        if (IS_ENABLED(CONFIG_ACPI) && ACPI_HANDLE(bus->dev))
                ret = sdw_acpi_find_slaves(bus);
+       else if (IS_ENABLED(CONFIG_OF) && bus->dev->of_node)
+               ret = sdw_of_find_slaves(bus);
        else
                ret = -ENOTSUPP; /* No ACPI/DT so error out */
  
diff --git a/drivers/soundwire/bus.h b/drivers/soundwire/bus.h
index 3048ca153f22..ee46befedbd1 100644
--- a/drivers/soundwire/bus.h
+++ b/drivers/soundwire/bus.h
@@ -15,6 +15,7 @@ static inline int sdw_acpi_find_slaves(struct sdw_bus *bus)
  }
  #endif
  
+int sdw_of_find_slaves(struct sdw_bus *bus);
  void sdw_extract_slave_id(struct sdw_bus *bus,
                          u64 addr, struct sdw_slave_id *id);
  
diff --git a/drivers/soundwire/slave.c b/drivers/soundwire/slave.c
index f39a5815e25d..3ef265d2ee89 100644
--- a/drivers/soundwire/slave.c
+++ b/drivers/soundwire/slave.c
@@ -2,6 +2,7 @@
  // Copyright(c) 2015-17 Intel Corporation.
  
  #include <linux/acpi.h>
+#include <linux/of.h>
  #include <linux/soundwire/sdw.h>
  #include <linux/soundwire/sdw_type.h>
  #include "bus.h"
@@ -35,6 +36,7 @@ static int sdw_slave_add(struct sdw_bus *bus,
  
  	slave->dev.release = sdw_slave_release;
        slave->dev.bus = &sdw_bus_type;
+       slave->dev.of_node = of_node_get(to_of_node(fwnode));
        slave->bus = bus;
        slave->status = SDW_SLAVE_UNATTACHED;
        slave->dev_num = 0;
@@ -112,3 +114,53 @@ int sdw_acpi_find_slaves(struct sdw_bus *bus)
  }
  
  #endif
+
+/*
+ * sdw_of_find_slaves() - Find Slave devices in master device tree node
+ * @bus: SDW bus instance
+ *
+ * Scans Master DT node for SDW child Slave devices and registers it.
+ */
+int sdw_of_find_slaves(struct sdw_bus *bus)
+{
+       struct device *dev = bus->dev;
+       struct device_node *node;
+
+       for_each_child_of_node(bus->dev->of_node, node) {
+               int link_id, sdw_version, ret, len;
+               const char *compat = NULL;
+               struct sdw_slave_id id;
+               const __be32 *addr;
+
+               compat = of_get_property(node, "compatible", NULL);
+               if (!compat)
+                       continue;
+
+               ret = sscanf(compat, "sdw%01x%04hx%04hx%02hhx", &sdw_version,
+                            &id.mfg_id, &id.part_id, &id.class_id);
+
+               if (ret != 4) {
+                       dev_err(dev, "Invalid compatible string found %s\n",
+                               compat);
+                       continue;
+               }
+
+               addr = of_get_property(node, "reg", &len);
+               if (!addr || (len < 2 * sizeof(u32))) {
+                       dev_err(dev, "Invalid Instance and Link ID\n");
+                       continue;
+               }
+
+               id.unique_id = be32_to_cpup(addr++);
+               link_id = be32_to_cpup(addr);

So here the link ID is obviously not in the address, so you are not 
using the MIPI spec as we discussed initially?

+               id.sdw_version = sdw_version;
+
+               /* Check for link_id match */
+               if (link_id != bus->link_id)
+                       continue;
+
+               sdw_slave_add(bus, &id, of_fwnode_handle(node));
+       }
+
+       return 0;
+}