linux/drivers/mmc/core
Sujit Reddy Thumma 597dd9d79c mmc: core: Use delayed work in clock gating framework
Current clock gating framework disables the MCI clock as soon as the
request is completed and enables it when a request arrives. This aggressive
clock gating framework, when enabled, cause following issues:

When there are back-to-back requests from the Queue layer, we unnecessarily
end up disabling and enabling the clocks between these requests since 8MCLK
clock cycles is a very short duration compared to the time delay between
back to back requests reaching the MMC layer. This overhead can effect the
overall performance depending on how long the clock enable and disable
calls take which is platform dependent. For example on some platforms we
can have clock control not on the local processor, but on a different
subsystem and the time taken to perform the clock enable/disable can add
significant overhead.

Also if the host controller driver decides to disable the host clock too
when mmc_set_ios function is called with ios.clock=0, it adds additional
delay and it is highly possible that the next request had already arrived
and unnecessarily blocked in enabling the clocks. This is seen frequently
when the processor is executing at high speeds and in multi-core platforms
thus reduces the overall throughput compared to if clock gating is
disabled.

Fix this by delaying turning off the clocks by posting request on
delayed workqueue. Also cancel the unscheduled pending work, if any,
when there is access to card.

sysfs entry is provided to tune the delay as needed, default
value set to 200ms.

Signed-off-by: Sujit Reddy Thumma <sthumma@codeaurora.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Chris Ball <cjb@laptop.org>
2012-01-11 23:58:41 -05:00
..
bus.c mmc: Fix implicit use of stat.h header in associated files 2011-10-31 19:32:07 -04:00
bus.h mmc: rename dev_to_mmc_card() to mmc_dev_to_card() 2010-10-23 21:11:12 +08:00
core.c mmc: core: Fix deadlock when the CONFIG_MMC_UNSAFE_RESUME is not defined 2011-12-10 16:18:39 -05:00
core.h mmc: core: Fix hangs related to insert/remove of cards 2011-10-26 16:32:01 -04:00
debugfs.c mmc: debugfs: expose the SDCLK frq in sys ios 2012-01-11 23:58:40 -05:00
host.c mmc: core: Use delayed work in clock gating framework 2012-01-11 23:58:41 -05:00
host.h mmc: rename mmc_host_clk_{ungate|gate} to mmc_host_clk_{hold|release} 2011-08-31 16:24:54 -04:00
Kconfig mmc: Aggressive clock gating framework 2011-01-08 22:48:03 -05:00
Makefile mmc: add per device quirk placeholder 2011-03-15 13:48:33 -04:00
mmc_ops.c mmc: Add export.h for EXPORT_SYMBOL/THIS_MODULE as required 2011-10-31 19:32:06 -04:00
mmc_ops.h mmc: core: support HPI send command 2011-10-26 16:32:29 -04:00
mmc.c mmc: core: Fix power_off_notify during suspend 2011-12-10 16:18:36 -05:00
quirks.c mmc: Add export.h for EXPORT_SYMBOL/THIS_MODULE as required 2011-10-31 19:32:06 -04:00
sd_ops.c mmc: Add export.h for EXPORT_SYMBOL/THIS_MODULE as required 2011-10-31 19:32:06 -04:00
sd_ops.h mmc: add erase, secure erase, trim and secure trim operations 2010-08-12 08:43:30 -07:00
sd.c mmc: sd: Macro name cleanup for high speed dtr 2012-01-11 23:58:40 -05:00
sd.h mmc: sd: add support for driver type selection 2011-05-24 23:53:24 -04:00
sdio_bus.c mmc: Add export.h for EXPORT_SYMBOL/THIS_MODULE as required 2011-10-31 19:32:06 -04:00
sdio_bus.h mmc: basic SDIO device model 2007-09-23 19:45:31 +02:00
sdio_cis.c mmc: replace printk with appropriate display macro 2011-10-26 16:32:22 -04:00
sdio_cis.h sdio: split up common and function CIS parsing 2007-09-23 20:44:22 +02:00
sdio_io.c mmc: sdio: Fix to support any block size optimally 2012-01-11 23:58:40 -05:00
sdio_irq.c mmc: Add export.h for EXPORT_SYMBOL/THIS_MODULE as required 2011-10-31 19:32:06 -04:00
sdio_ops.c mmc: sdio: Fix to support any block size optimally 2012-01-11 23:58:40 -05:00
sdio_ops.h sdio: recognize io card without powercycle 2010-03-12 15:52:28 -08:00
sdio.c mmc: recognise SDIO cards with SDIO_CCCR_REV 3.00 2011-10-26 16:32:31 -04:00