projects / deliverable / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| 371a689f AW |
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 | ||
| dfe86cba AH |
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 | serial Product Serial Number (from CID Register) | |
| 26 | erase_size Erase group size | |
| 27 | preferred_erase_size Preferred erase size | |
| 188cc042 LP |
28 | raw_rpmb_size_mult RPMB partition size |
| 29 | rel_sectors Reliable write sector count | |
| dfe86cba AH |
30 | |
| 31 | Note on Erase Size and Preferred Erase Size: | |
| 32 | ||
| 33 | "erase_size" is the minimum size, in bytes, of an erase | |
| 34 | operation. For MMC, "erase_size" is the erase group size | |
| 35 | reported by the card. Note that "erase_size" does not apply | |
| 36 | to trim or secure trim operations where the minimum size is | |
| 37 | always one 512 byte sector. For SD, "erase_size" is 512 | |
| 38 | if the card is block-addressed, 0 otherwise. | |
| 39 | ||
| 40 | SD/MMC cards can erase an arbitrarily large area up to and | |
| 41 | including the whole card. When erasing a large area it may | |
| 42 | be desirable to do it in smaller chunks for three reasons: | |
| 43 | 1. A single erase command will make all other I/O on | |
| 44 | the card wait. This is not a problem if the whole card | |
| 45 | is being erased, but erasing one partition will make | |
| 46 | I/O for another partition on the same card wait for the | |
| 47 | duration of the erase - which could be a several | |
| 48 | minutes. | |
| 49 | 2. To be able to inform the user of erase progress. | |
| 50 | 3. The erase timeout becomes too large to be very | |
| 51 | useful. Because the erase timeout contains a margin | |
| 52 | which is multiplied by the size of the erase area, | |
| 53 | the value can end up being several minutes for large | |
| 54 | areas. | |
| 55 | ||
| 56 | "erase_size" is not the most efficient unit to erase | |
| 57 | (especially for SD where it is just one sector), | |
| 58 | hence "preferred_erase_size" provides a good chunk | |
| 59 | size for erasing large areas. | |
| 60 | ||
| 61 | For MMC, "preferred_erase_size" is the high-capacity | |
| 62 | erase size if a card specifies one, otherwise it is | |
| 63 | based on the capacity of the card. | |
| 64 | ||
| 65 | For SD, "preferred_erase_size" is the allocation unit | |
| 66 | size specified by the card. | |
| 67 | ||
| 68 | "preferred_erase_size" is in bytes. | |
| 597dd9d7 | 69 | |
| 188cc042 LP |
70 | Note on raw_rpmb_size_mult: |
| 71 | "raw_rpmb_size_mult" is a mutliple of 128kB block. | |
| 72 | RPMB size in byte is calculated by using the following equation: | |
| 73 | RPMB partition size = 128kB x raw_rpmb_size_mult | |
| 74 | ||
| 597dd9d7 SRT |
75 | SD/MMC/SDIO Clock Gating Attribute |
| 76 | ================================== | |
| 77 | ||
| 78 | Read and write access is provided to following attribute. | |
| 79 | This attribute appears only if CONFIG_MMC_CLKGATE is enabled. | |
| 80 | ||
| 4137e504 | 81 | clkgate_delay Tune the clock gating delay with desired value in milliseconds. |
| 597dd9d7 SRT |
82 | |
| 83 | echo <desired delay> > /sys/class/mmc_host/mmcX/clkgate_delay |