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linux/Documentation/mmc/mmc-dev-attrs.txt

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mmc: MMC boot partitions support. Allows device MMC boot partitions to be accessed. MMC partitions are treated effectively as separate block devices on the same MMC card. Signed-off-by: Andrei Warkentin <andreiw@motorola.com> Acked-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Chris Ball <cjb@laptop.org>
2011-04-11 23:10:25 +00:00
SD and MMC Block Device Attributes
==================================
These attributes are defined for the block devices associated with the
SD or MMC device.
The following attributes are read/write.
force_ro Enforce read-only access even if write protect switch is off.
mmc: add erase, secure erase, trim and secure trim operations SD/MMC cards tend to support an erase operation. In addition, eMMC v4.4 cards can support secure erase, trim and secure trim operations that are all variants of the basic erase command. SD/MMC device attributes "erase_size" and "preferred_erase_size" have been added. "erase_size" is the minimum size, in bytes, of an erase operation. For MMC, "erase_size" is the erase group size reported by the card. Note that "erase_size" does not apply to trim or secure trim operations where the minimum size is always one 512 byte sector. For SD, "erase_size" is 512 if the card is block-addressed, 0 otherwise. SD/MMC cards can erase an arbitrarily large area up to and including the whole card. When erasing a large area it may be desirable to do it in smaller chunks for three reasons: 1. A single erase command will make all other I/O on the card wait. This is not a problem if the whole card is being erased, but erasing one partition will make I/O for another partition on the same card wait for the duration of the erase - which could be a several minutes. 2. To be able to inform the user of erase progress. 3. The erase timeout becomes too large to be very useful. Because the erase timeout contains a margin which is multiplied by the size of the erase area, the value can end up being several minutes for large areas. "erase_size" is not the most efficient unit to erase (especially for SD where it is just one sector), hence "preferred_erase_size" provides a good chunk size for erasing large areas. For MMC, "preferred_erase_size" is the high-capacity erase size if a card specifies one, otherwise it is based on the capacity of the card. For SD, "preferred_erase_size" is the allocation unit size specified by the card. "preferred_erase_size" is in bytes. Signed-off-by: Adrian Hunter <adrian.hunter@nokia.com> Acked-by: Jens Axboe <axboe@kernel.dk> Cc: Kyungmin Park <kmpark@infradead.org> Cc: Madhusudhan Chikkature <madhu.cr@ti.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Ben Gardiner <bengardiner@nanometrics.ca> Cc: <linux-mmc@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-08-11 21:17:46 +00:00
SD and MMC Device Attributes
============================
All attributes are read-only.
cid Card Identifaction Register
csd Card Specific Data Register
scr SD Card Configuration Register (SD only)
date Manufacturing Date (from CID Register)
fwrev Firmware/Product Revision (from CID Register) (SD and MMCv1 only)
hwrev Hardware/Product Revision (from CID Register) (SD and MMCv1 only)
manfid Manufacturer ID (from CID Register)
name Product Name (from CID Register)
oemid OEM/Application ID (from CID Register)
serial Product Serial Number (from CID Register)
erase_size Erase group size
preferred_erase_size Preferred erase size
Note on Erase Size and Preferred Erase Size:
"erase_size" is the minimum size, in bytes, of an erase
operation. For MMC, "erase_size" is the erase group size
reported by the card. Note that "erase_size" does not apply
to trim or secure trim operations where the minimum size is
always one 512 byte sector. For SD, "erase_size" is 512
if the card is block-addressed, 0 otherwise.
SD/MMC cards can erase an arbitrarily large area up to and
including the whole card. When erasing a large area it may
be desirable to do it in smaller chunks for three reasons:
1. A single erase command will make all other I/O on
the card wait. This is not a problem if the whole card
is being erased, but erasing one partition will make
I/O for another partition on the same card wait for the
duration of the erase - which could be a several
minutes.
2. To be able to inform the user of erase progress.
3. The erase timeout becomes too large to be very
useful. Because the erase timeout contains a margin
which is multiplied by the size of the erase area,
the value can end up being several minutes for large
areas.
"erase_size" is not the most efficient unit to erase
(especially for SD where it is just one sector),
hence "preferred_erase_size" provides a good chunk
size for erasing large areas.
For MMC, "preferred_erase_size" is the high-capacity
erase size if a card specifies one, otherwise it is
based on the capacity of the card.
For SD, "preferred_erase_size" is the allocation unit
size specified by the card.
"preferred_erase_size" is in bytes.
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>
2011-11-14 08:23:29 +00:00
SD/MMC/SDIO Clock Gating Attribute
==================================
Read and write access is provided to following attribute.
This attribute appears only if CONFIG_MMC_CLKGATE is enabled.
mmc: core: Fixup delayed work clock gating patch c31b50e (mmc: core: Use delayed work in clock gating framework, 2011-11-14) missed a few things during review: o A useless pr_info() o milliseconds was written as two words o The sysfs file had units in its output Fix all three problems. Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> Cc: Sujit Reddy Thumma <sthumma@codeaurora.org> Signed-off-by: Chris Ball <cjb@laptop.org>
2011-12-05 18:28:44 +00:00
clkgate_delay Tune the clock gating delay with desired value in milliseconds.
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>
2011-11-14 08:23:29 +00:00
echo <desired delay> > /sys/class/mmc_host/mmcX/clkgate_delay
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