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- 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.
- 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)
- prv Product Revision (from CID Register) (SD and MMCv4 only)
- serial Product Serial Number (from CID Register)
- erase_size Erase group size
- preferred_erase_size Preferred erase size
- raw_rpmb_size_mult RPMB partition size
- rel_sectors Reliable write sector count
- 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.
- Note on raw_rpmb_size_mult:
- "raw_rpmb_size_mult" is a mutliple of 128kB block.
- RPMB size in byte is calculated by using the following equation:
- RPMB partition size = 128kB x raw_rpmb_size_mult
- 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.
- clkgate_delay Tune the clock gating delay with desired value in milliseconds.
- echo <desired delay> > /sys/class/mmc_host/mmcX/clkgate_delay
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