[PATCH v5 4/5] mmc: core: Add sdio_retune_hold_now() and sdio_retune_release()

[Douglas Anderson]

We want SDIO drivers to be able to temporarily stop retuning when the
driver knows that the SDIO card is not in a state where retuning will
work (maybe because the card is asleep).  We'll move the relevant
functions to a place where drivers can call them.

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
Acked-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
---
Patches #2 - #5 will go through Ulf's tree.

I've CCed stable@ here without a version tag.  As per Adrian Hunter
this patch applies cleanly to 4.18+ so that would be an easy first
target.  However, if someone were so inclined they could provide
further backports.  As per Adrian [1] the root problem has existed for
~4 years.

[1] https://lkml.kernel.org/r/4f39e152-04ba-a64e-985a-df93e6d15ff8@xxxxxxxxx

Changes in v5: None
Changes in v4:
- Moved retune hold/release to SDIO API (Adrian).

Changes in v3:
- ("mmc: core: Export mmc_retune_hold_now() mmc_retune_release()") new for v3.

Changes in v2: None

 drivers/mmc/core/sdio_io.c    | 40 +++++++++++++++++++++++++++++++++++
 include/linux/mmc/sdio_func.h |  3 +++
 2 files changed, 43 insertions(+)

diff --git a/drivers/mmc/core/sdio_io.c b/drivers/mmc/core/sdio_io.c
index 0acb1a29c968..2ba00acf64e6 100644
--- a/drivers/mmc/core/sdio_io.c
+++ b/drivers/mmc/core/sdio_io.c
@@ -15,6 +15,7 @@
 #include "sdio_ops.h"
 #include "core.h"
 #include "card.h"
+#include "host.h"
 
 /**
  *	sdio_claim_host - exclusively claim a bus for a certain SDIO function
@@ -771,3 +772,42 @@ void sdio_retune_crc_enable(struct sdio_func *func)
 	func->card->host->retune_crc_disable = false;
 }
 EXPORT_SYMBOL_GPL(sdio_retune_crc_enable);
+
+/**
+ *	sdio_retune_hold_now - start deferring retuning requests till release
+ *	@func: SDIO function attached to host
+ *
+ *	This function can be called if it's currently a bad time to do
+ *	a retune of the SDIO card.  Retune requests made during this time
+ *	will be held and we'll actually do the retune sometime after the
+ *	release.
+ *
+ *	This function could be useful if an SDIO card is in a power state
+ *	where it can respond to a small subset of commands that doesn't
+ *	include the retuning command.  Care should be taken when using
+ *	this function since (presumably) the retuning request we might be
+ *	deferring was made for a good reason.
+ *
+ *	This function should be called while the host is claimed.
+ */
+void sdio_retune_hold_now(struct sdio_func *func)
+{
+	mmc_retune_hold_now(func->card->host);
+}
+EXPORT_SYMBOL_GPL(sdio_retune_hold_now);
+
+/**
+ *	sdio_retune_release - signal that it's OK to retune now
+ *	@func: SDIO function attached to host
+ *
+ *	This is the complement to sdio_retune_hold_now().  Calling this
+ *	function won't make a retune happen right away but will allow
+ *	them to be scheduled normally.
+ *
+ *	This function should be called while the host is claimed.
+ */
+void sdio_retune_release(struct sdio_func *func)
+{
+	mmc_retune_release(func->card->host);
+}
+EXPORT_SYMBOL_GPL(sdio_retune_release);
diff --git a/include/linux/mmc/sdio_func.h b/include/linux/mmc/sdio_func.h
index 4820e6d09dac..5a177f7a83c3 100644
--- a/include/linux/mmc/sdio_func.h
+++ b/include/linux/mmc/sdio_func.h
@@ -170,4 +170,7 @@ extern int sdio_set_host_pm_flags(struct sdio_func *func, mmc_pm_flag_t flags);
 extern void sdio_retune_crc_disable(struct sdio_func *func);
 extern void sdio_retune_crc_enable(struct sdio_func *func);
 
+extern void sdio_retune_hold_now(struct sdio_func *func);
+extern void sdio_retune_release(struct sdio_func *func);
+
 #endif /* LINUX_MMC_SDIO_FUNC_H */
-- 
2.22.0.410.gd8fdbe21b5-goog