mmc: Aggressive clock gating framework
This patch modifies the MMC core code to optionally call the set_ios()
operation on the driver with the clock frequency set to 0 (gate) after
a grace period of at least 8 MCLK cycles, then restore it (ungate)
before any new request. This gives the driver the option to shut down
the MCI clock to the MMC/SD card when the clock frequency is 0, i.e.
the core has stated that the MCI clock does not need to be generated.
It is inspired by existing clock gating code found in the OMAP and
Atmel drivers and brings this up to the host abstraction. Gating is
performed before and after any MMC request.
This patchset implements this for the MMCI/PL180 MMC/SD host controller,
but it should be simple to switch OMAP/Atmel over to using this instead.
mmc_set_{gated,ungated}() add variable protection to the state holders
for the clock gating code. This is particularly important when ordinary
.set_ios() calls would race with the .set_ios() call resulting from a
delayed gate operation.
Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Reviewed-by: Chris Ball <cjb@laptop.org>
Tested-by: Chris Ball <cjb@laptop.org>
Signed-off-by: Chris Ball <cjb@laptop.org>
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 30f6fad..381c77f 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -172,6 +172,16 @@
mmc_pm_flag_t pm_caps; /* supported pm features */
+#ifdef CONFIG_MMC_CLKGATE
+ int clk_requests; /* internal reference counter */
+ unsigned int clk_delay; /* number of MCI clk hold cycles */
+ bool clk_gated; /* clock gated */
+ struct work_struct clk_gate_work; /* delayed clock gate */
+ unsigned int clk_old; /* old clock value cache */
+ spinlock_t clk_lock; /* lock for clk fields */
+ struct mutex clk_gate_mutex; /* mutex for clock gating */
+#endif
+
/* host specific block data */
unsigned int max_seg_size; /* see blk_queue_max_segment_size */
unsigned short max_segs; /* see blk_queue_max_segments */