soundwire: bus: add PM/no-PM versions of read/write functions

Add support for pm_runtime with the appropriate error checks for
sdw_write/read functions, e.g. when pm_runtime is not supported.

Also expose internal functions without pm_runtime support, which are
required to perform any sort of suspend/resume operation, as well as
any enumeration tasks.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20200115000844.14695-5-pierre-louis.bossart@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/soundwire/bus.c

@@ -317,14 +317,15 @@ int sdw_fill_msg(struct sdw_msg *msg, struct sdw_slave *slave,
 	return 0;
 }
 
-/**
- * sdw_nread() - Read "n" contiguous SDW Slave registers
- * @slave: SDW Slave
- * @addr: Register address
- * @count: length
- * @val: Buffer for values to be read
+/*
+ * Read/Write IO functions.
+ * no_pm versions can only be called by the bus, e.g. while enumerating or
+ * handling suspend-resume sequences.
+ * all clients need to use the pm versions
  */
-int sdw_nread(struct sdw_slave *slave, u32 addr, size_t count, u8 *val)
+
+static int
+sdw_nread_no_pm(struct sdw_slave *slave, u32 addr, size_t count, u8 *val)
 {
 	struct sdw_msg msg;
 	int ret;
@@ -334,11 +335,48 @@ int sdw_nread(struct sdw_slave *slave, u32 addr, size_t count, u8 *val)
 	if (ret < 0)
 		return ret;
 
-	ret = pm_runtime_get_sync(slave->bus->dev);
+	return sdw_transfer(slave->bus, &msg);
+}
+
+static int
+sdw_nwrite_no_pm(struct sdw_slave *slave, u32 addr, size_t count, u8 *val)
+{
+	struct sdw_msg msg;
+	int ret;
+
+	ret = sdw_fill_msg(&msg, slave, addr, count,
+			   slave->dev_num, SDW_MSG_FLAG_WRITE, val);
 	if (ret < 0)
 		return ret;
 
-	ret = sdw_transfer(slave->bus, &msg);
+	return sdw_transfer(slave->bus, &msg);
+}
+
+static int sdw_write_no_pm(struct sdw_slave *slave, u32 addr, u8 value)
+{
+	return sdw_nwrite_no_pm(slave, addr, 1, &value);
+}
+
+/**
+ * sdw_nread() - Read "n" contiguous SDW Slave registers
+ * @slave: SDW Slave
+ * @addr: Register address
+ * @count: length
+ * @val: Buffer for values to be read
+ */
+int sdw_nread(struct sdw_slave *slave, u32 addr, size_t count, u8 *val)
+{
+	int ret;
+
+	ret = pm_runtime_get_sync(slave->bus->dev);
+	if (ret < 0 && ret != -EACCES) {
+		pm_runtime_put_noidle(slave->bus->dev);
+		return ret;
+	}
+
+	ret = sdw_nread_no_pm(slave, addr, count, val);
+
+	pm_runtime_mark_last_busy(slave->bus->dev);
 	pm_runtime_put(slave->bus->dev);
 
 	return ret;
@@ -354,19 +392,17 @@ EXPORT_SYMBOL(sdw_nread);
  */
 int sdw_nwrite(struct sdw_slave *slave, u32 addr, size_t count, u8 *val)
 {
-	struct sdw_msg msg;
 	int ret;
 
-	ret = sdw_fill_msg(&msg, slave, addr, count,
-			   slave->dev_num, SDW_MSG_FLAG_WRITE, val);
-	if (ret < 0)
-		return ret;
-
 	ret = pm_runtime_get_sync(slave->bus->dev);
-	if (ret < 0)
+	if (ret < 0 && ret != -EACCES) {
+		pm_runtime_put_noidle(slave->bus->dev);
 		return ret;
+	}
 
-	ret = sdw_transfer(slave->bus, &msg);
+	ret = sdw_nwrite_no_pm(slave, addr, count, val);
+
+	pm_runtime_mark_last_busy(slave->bus->dev);
 	pm_runtime_put(slave->bus->dev);
 
 	return ret;