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Andrei Warkentin371a6892011-04-11 18:10:25 -05001SD and MMC Block Device Attributes
2==================================
3
4These attributes are defined for the block devices associated with the
5SD or MMC device.
6
7The following attributes are read/write.
8
9 force_ro Enforce read-only access even if write protect switch is off.
10
Adrian Hunterdfe86cb2010-08-11 14:17:46 -070011SD and MMC Device Attributes
12============================
13
14All 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)
Bernie Thompson51e7e8b2013-02-27 12:19:17 -080025 prv Product Revision (from CID Register) (SD and MMCv4 only)
Adrian Hunterdfe86cb2010-08-11 14:17:46 -070026 serial Product Serial Number (from CID Register)
27 erase_size Erase group size
28 preferred_erase_size Preferred erase size
Loic Pallardy188cc042012-08-06 17:12:29 +020029 raw_rpmb_size_mult RPMB partition size
30 rel_sectors Reliable write sector count
Adrian Hunterdfe86cb2010-08-11 14:17:46 -070031
32Note 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.
Sujit Reddy Thumma597dd9d792011-11-14 13:53:29 +053070
Loic Pallardy188cc042012-08-06 17:12:29 +020071Note 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
Sujit Reddy Thumma597dd9d792011-11-14 13:53:29 +053076SD/MMC/SDIO Clock Gating Attribute
77==================================
78
79Read and write access is provided to following attribute.
80This attribute appears only if CONFIG_MMC_CLKGATE is enabled.
81
Stephen Boyd4137e502011-12-05 10:28:44 -080082 clkgate_delay Tune the clock gating delay with desired value in milliseconds.
Sujit Reddy Thumma597dd9d792011-11-14 13:53:29 +053083
84echo <desired delay> > /sys/class/mmc_host/mmcX/clkgate_delay