regmap: sdw-mbq: Add support for SDCA deferred controls

The SDCA specification allows for controls to be deferred. In the case
of a deferred control the device will return COMMAND_IGNORED to the
8-bit operation that would cause the value to commit. Which is the
final 8-bits on a write, or the first 8-bits on a read. In the case of
receiving a defer, the regmap will poll the SDCA function busy bit,
after which the transaction will be retried, returning an error if the
function busy does not clear within a chip specific timeout. Since
this is common SDCA functionality which is the 99% use-case for MBQs
it makes sense to incorporate this functionality into the register
map. If no MBQ configuration is specified, the behaviour will default
to the existing behaviour.

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://patch.msgid.link/20250107154408.814455-5-ckeepax@opensource.cirrus.com
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.dev>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 15 insertions, 0 deletions

diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index dd96a22f5657..198067d3cf10 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -510,11 +510,26 @@ struct regmap_range_cfg {
  * struct regmap_sdw_mbq_cfg - Configuration for Multi-Byte Quantities
  *
  * @mbq_size: Callback returning the actual size of the given register.
+ * @deferrable: Callback returning true if the hardware can defer
+ *              transactions to the given register. Deferral should
+ *              only be used by SDCA parts and typically which controls
+ *              are deferrable will be specified in either as a hard
+ *              coded list or from the DisCo tables in the platform
+ *              firmware.
+ *
+ * @timeout_us: The time in microseconds after which waiting for a deferred
+ *              transaction should time out.
+ * @retry_us: The time in microseconds between polls of the function busy
+ *            status whilst waiting for an opportunity to retry a deferred
+ *            transaction.
  *
  * Provides additional configuration required for SoundWire MBQ register maps.
  */
 struct regmap_sdw_mbq_cfg {
 	int (*mbq_size)(struct device *dev, unsigned int reg);
+	bool (*deferrable)(struct device *dev, unsigned int reg);
+	unsigned long timeout_us;
+	unsigned long retry_us;
 };
 
 struct regmap_async;