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    • Adrian Hunter's avatar
      mmc: add erase, secure erase, trim and secure trim operations · dfe86cba
      Adrian Hunter authored
      SD/MMC cards tend to support an erase operation.  In addition, eMMC v4.4
      cards can support secure erase, trim and secure trim operations that are
      all variants of the basic erase command.
      
      SD/MMC device attributes "erase_size" and "preferred_erase_size" have been
      added.
      
      "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.
      Signed-off-by: default avatarAdrian Hunter <adrian.hunter@nokia.com>
      Acked-by: default avatarJens Axboe <axboe@kernel.dk>
      Cc: Kyungmin Park <kmpark@infradead.org>
      Cc: Madhusudhan Chikkature <madhu.cr@ti.com>
      Cc: Christoph Hellwig <hch@lst.de>
      Cc: Ben Gardiner <bengardiner@nanometrics.ca>
      Cc: <linux-mmc@vger.kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      dfe86cba