[PATCH 4/7] soundwire/regmap: use _no_pm functions in regmap_read/write

[Bard Liao]

sdw_update_slave_status will be invoked when a codec is attached,
and the codec driver will initialize the codec with regmap functions
while the codec device is pm_runtime suspended.

regmap routines currently rely on regular SoundWire IO functions,
which will call pm_runtime_get_sync()/put_autosuspend.

This causes a deadlock where the resume routine waits for an
initialization complete signal that while the initialization complete
can only be reached when the resume completes.

The only solution if we allow regmap functions to be used in resume
operations as well as during codec initialization is to use _no_pm
routines. The duty of making sure the bus is operational needs to be
handled above the regmap level.

Fixes: 7c22ce6e21840 ('regmap: Add SoundWire bus support')
Signed-off-by: Bard Liao <yung-chuan.liao@xxxxxxxxxxxxxxx>
Reviewed-by: Rander Wang <rander.wang@xxxxxxxxxxxxxxx>
---
 drivers/base/regmap/regmap-sdw.c | 4 ++--
 drivers/soundwire/bus.c          | 6 ++++--
 include/linux/soundwire/sdw.h    | 2 ++
 3 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/base/regmap/regmap-sdw.c b/drivers/base/regmap/regmap-sdw.c
index c92d614b4943..4b8d2d010cab 100644
--- a/drivers/base/regmap/regmap-sdw.c
+++ b/drivers/base/regmap/regmap-sdw.c
@@ -11,7 +11,7 @@ static int regmap_sdw_write(void *context, unsigned int reg, unsigned int val)
 	struct device *dev = context;
 	struct sdw_slave *slave = dev_to_sdw_dev(dev);
 
-	return sdw_write(slave, reg, val);
+	return sdw_write_no_pm(slave, reg, val);
 }
 
 static int regmap_sdw_read(void *context, unsigned int reg, unsigned int *val)
@@ -20,7 +20,7 @@ static int regmap_sdw_read(void *context, unsigned int reg, unsigned int *val)
 	struct sdw_slave *slave = dev_to_sdw_dev(dev);
 	int read;
 
-	read = sdw_read(slave, reg);
+	read = sdw_read_no_pm(slave, reg);
 	if (read < 0)
 		return read;
 
diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
index 86c339d77a39..c5ea59673dee 100644
--- a/drivers/soundwire/bus.c
+++ b/drivers/soundwire/bus.c
@@ -405,10 +405,11 @@ sdw_nwrite_no_pm(struct sdw_slave *slave, u32 addr, size_t count, u8 *val)
 	return sdw_transfer(slave->bus, &msg);
 }
 
-static int sdw_write_no_pm(struct sdw_slave *slave, u32 addr, u8 value)
+int sdw_write_no_pm(struct sdw_slave *slave, u32 addr, u8 value)
 {
 	return sdw_nwrite_no_pm(slave, addr, 1, &value);
 }
+EXPORT_SYMBOL(sdw_write_no_pm);
 
 static int
 sdw_bread_no_pm(struct sdw_bus *bus, u16 dev_num, u32 addr)
@@ -476,7 +477,7 @@ int sdw_bwrite_no_pm_unlocked(struct sdw_bus *bus, u16 dev_num, u32 addr, u8 val
 }
 EXPORT_SYMBOL(sdw_bwrite_no_pm_unlocked);
 
-static int
+int
 sdw_read_no_pm(struct sdw_slave *slave, u32 addr)
 {
 	u8 buf;
@@ -488,6 +489,7 @@ sdw_read_no_pm(struct sdw_slave *slave, u32 addr)
 	else
 		return buf;
 }
+EXPORT_SYMBOL(sdw_read_no_pm);
 
 static int sdw_update_no_pm(struct sdw_slave *slave, u32 addr, u8 mask, u8 val)
 {
diff --git a/include/linux/soundwire/sdw.h b/include/linux/soundwire/sdw.h
index f0b01b728640..d08039d65825 100644
--- a/include/linux/soundwire/sdw.h
+++ b/include/linux/soundwire/sdw.h
@@ -1005,6 +1005,8 @@ int sdw_bus_exit_clk_stop(struct sdw_bus *bus);
 
 int sdw_read(struct sdw_slave *slave, u32 addr);
 int sdw_write(struct sdw_slave *slave, u32 addr, u8 value);
+int sdw_write_no_pm(struct sdw_slave *slave, u32 addr, u8 value);
+int sdw_read_no_pm(struct sdw_slave *slave, u32 addr);
 int sdw_nread(struct sdw_slave *slave, u32 addr, size_t count, u8 *val);
 int sdw_nwrite(struct sdw_slave *slave, u32 addr, size_t count, u8 *val);
 
-- 
2.17.1