51e7e8b632
The JEDEC MMC v4 spec defines a new PRV value in place of the original fwrev and hwrev specified in v1. We can expose this in the kernel to enable user space to more easily determine the product revision of a given MMC. Signed-off-by: Bernie Thompson <bhthompson@chromium.org> Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org> Signed-off-by: Chris Ball <cjb@laptop.org>
84 lines
3.1 KiB
Text
84 lines
3.1 KiB
Text
SD and MMC Block Device Attributes
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==================================
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These attributes are defined for the block devices associated with the
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SD or MMC device.
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The following attributes are read/write.
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force_ro Enforce read-only access even if write protect switch is off.
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SD and MMC Device Attributes
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============================
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All attributes are read-only.
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cid Card Identifaction Register
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csd Card Specific Data Register
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scr SD Card Configuration Register (SD only)
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date Manufacturing Date (from CID Register)
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fwrev Firmware/Product Revision (from CID Register) (SD and MMCv1 only)
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hwrev Hardware/Product Revision (from CID Register) (SD and MMCv1 only)
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manfid Manufacturer ID (from CID Register)
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name Product Name (from CID Register)
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oemid OEM/Application ID (from CID Register)
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prv Product Revision (from CID Register) (SD and MMCv4 only)
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serial Product Serial Number (from CID Register)
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erase_size Erase group size
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preferred_erase_size Preferred erase size
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raw_rpmb_size_mult RPMB partition size
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rel_sectors Reliable write sector count
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Note on Erase Size and Preferred Erase Size:
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"erase_size" is the minimum size, in bytes, of an erase
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operation. For MMC, "erase_size" is the erase group size
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reported by the card. Note that "erase_size" does not apply
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to trim or secure trim operations where the minimum size is
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always one 512 byte sector. For SD, "erase_size" is 512
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if the card is block-addressed, 0 otherwise.
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SD/MMC cards can erase an arbitrarily large area up to and
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including the whole card. When erasing a large area it may
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be desirable to do it in smaller chunks for three reasons:
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1. A single erase command will make all other I/O on
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the card wait. This is not a problem if the whole card
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is being erased, but erasing one partition will make
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I/O for another partition on the same card wait for the
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duration of the erase - which could be a several
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minutes.
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2. To be able to inform the user of erase progress.
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3. The erase timeout becomes too large to be very
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useful. Because the erase timeout contains a margin
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which is multiplied by the size of the erase area,
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the value can end up being several minutes for large
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areas.
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"erase_size" is not the most efficient unit to erase
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(especially for SD where it is just one sector),
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hence "preferred_erase_size" provides a good chunk
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size for erasing large areas.
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For MMC, "preferred_erase_size" is the high-capacity
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erase size if a card specifies one, otherwise it is
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based on the capacity of the card.
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For SD, "preferred_erase_size" is the allocation unit
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size specified by the card.
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"preferred_erase_size" is in bytes.
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Note on raw_rpmb_size_mult:
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"raw_rpmb_size_mult" is a mutliple of 128kB block.
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RPMB size in byte is calculated by using the following equation:
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RPMB partition size = 128kB x raw_rpmb_size_mult
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SD/MMC/SDIO Clock Gating Attribute
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==================================
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Read and write access is provided to following attribute.
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This attribute appears only if CONFIG_MMC_CLKGATE is enabled.
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clkgate_delay Tune the clock gating delay with desired value in milliseconds.
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echo <desired delay> > /sys/class/mmc_host/mmcX/clkgate_delay
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