• David Brownell's avatar
    MMC core learns about SPI · af517150
    David Brownell authored
    
    
    Teach the MMC/SD/SDIO core about using SPI mode.
    
     - Use mmc_host_is_spi() so enumeration works through SPI signaling
       and protocols, not just the native versions.
    
     - Provide the SPI response type flags with each request issued,
       including requests from the new lock/unlock code.
    
     - Understand that cmd->resp[0] and mmc_get_status() results for SPI
       return different values than for "native" MMC/SD protocol; this
       affects resetting, checking card lock status, and some others.
    
     - Understand that some commands act a bit differently ... notably:
         * OP_COND command doesn't return the OCR
         * APP_CMD status doesn't have an R1_APP_CMD analogue
    
    Those changes required some new and updated primitives:
    
     - Provide utilities to access two SPI-only requests, and one
       request that wasn't previously needed:
         * mmc_spi_read_ocr() ... SPI only
         * mmc_spi_set_crc() ... SPI only (override by module parm)
         * mmc_send_cid() ... for use without broadcast mode
    
     - Updated internal routines:
         * Previous mmc_send_csd() modified into mmc_send_cxd_native();
           it uses native "R2" responses, which include 16 bytes of data.
         * Previous mmc_send_ext_csd() becomes new mmc_send_cxd_data()
           helper for command-and-data access
         * Bugfix to that mmc_send_cxd_data() code:  dma-to-stack is
           unsafe/nonportable, so kmalloc a bounce buffer instead.
    
     - Modified mmc_send_ext_csd() now uses mmc_send_cxd_data() helper
    
     - Modified mmc_send_csd(), and new mmc_spi_send_cid(), routines use
       those helper routines based on whether they're native or SPI
    
    The newest categories of cards supported by the MMC stack aren't expected
    to work yet with SPI:  MMC or SD cards with over 4GB data, and SDIO.
    All those cards support SPI mode, so eventually they should work too.
    
    Signed-off-by: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
    Signed-off-by: default avatarPierre Ossman <drzeus@drzeus.cx>
    af517150