Based on kernel version 4.0. Page generated on 2015-04-14 21:25 EST.
1 SD and MMC Block Device Attributes 2 ================================== 3 4 These attributes are defined for the block devices associated with the 5 SD or MMC device. 6 7 The following attributes are read/write. 8 9 force_ro Enforce read-only access even if write protect switch is off. 10 11 SD and MMC Device Attributes 12 ============================ 13 14 All attributes are read-only. 15 16 cid Card Identifaction Register 17 csd Card Specific Data Register 18 scr SD Card Configuration Register (SD only) 19 date Manufacturing Date (from CID Register) 20 fwrev Firmware/Product Revision (from CID Register) (SD and MMCv1 only) 21 hwrev Hardware/Product Revision (from CID Register) (SD and MMCv1 only) 22 manfid Manufacturer ID (from CID Register) 23 name Product Name (from CID Register) 24 oemid OEM/Application ID (from CID Register) 25 prv Product Revision (from CID Register) (SD and MMCv4 only) 26 serial Product Serial Number (from CID Register) 27 erase_size Erase group size 28 preferred_erase_size Preferred erase size 29 raw_rpmb_size_mult RPMB partition size 30 rel_sectors Reliable write sector count 31 32 Note on Erase Size and Preferred Erase Size: 33 34 "erase_size" is the minimum size, in bytes, of an erase 35 operation. For MMC, "erase_size" is the erase group size 36 reported by the card. Note that "erase_size" does not apply 37 to trim or secure trim operations where the minimum size is 38 always one 512 byte sector. For SD, "erase_size" is 512 39 if the card is block-addressed, 0 otherwise. 40 41 SD/MMC cards can erase an arbitrarily large area up to and 42 including the whole card. When erasing a large area it may 43 be desirable to do it in smaller chunks for three reasons: 44 1. A single erase command will make all other I/O on 45 the card wait. This is not a problem if the whole card 46 is being erased, but erasing one partition will make 47 I/O for another partition on the same card wait for the 48 duration of the erase - which could be a several 49 minutes. 50 2. To be able to inform the user of erase progress. 51 3. The erase timeout becomes too large to be very 52 useful. Because the erase timeout contains a margin 53 which is multiplied by the size of the erase area, 54 the value can end up being several minutes for large 55 areas. 56 57 "erase_size" is not the most efficient unit to erase 58 (especially for SD where it is just one sector), 59 hence "preferred_erase_size" provides a good chunk 60 size for erasing large areas. 61 62 For MMC, "preferred_erase_size" is the high-capacity 63 erase size if a card specifies one, otherwise it is 64 based on the capacity of the card. 65 66 For SD, "preferred_erase_size" is the allocation unit 67 size specified by the card. 68 69 "preferred_erase_size" is in bytes. 70 71 Note on raw_rpmb_size_mult: 72 "raw_rpmb_size_mult" is a mutliple of 128kB block. 73 RPMB size in byte is calculated by using the following equation: 74 RPMB partition size = 128kB x raw_rpmb_size_mult 75 76 SD/MMC/SDIO Clock Gating Attribute 77 ================================== 78 79 Read and write access is provided to following attribute. 80 This attribute appears only if CONFIG_MMC_CLKGATE is enabled. 81 82 clkgate_delay Tune the clock gating delay with desired value in milliseconds. 83 84 echo <desired delay> > /sys/class/mmc_host/mmcX/clkgate_delay