Messages in this thread | | | Date | Thu, 2 Feb 2006 09:36:57 +0000 | From | Russell King <> | Subject | Re: Purpose of MMC_DATA_MULTI? |
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On Wed, Feb 01, 2006 at 10:37:12AM +0100, Pierre Ossman wrote: > Russell King wrote: > > On Wed, Feb 01, 2006 at 07:40:26AM +0100, Pierre Ossman wrote: > >> I noticed that a new transfer flag was recently added to the MMC layer > >> without any immediate users, the MMC_DATA_MULTI flag. I'm guessing the > >> purpose of the flag is to indicate the difference between > >> MMC_READ_SINGLE_BLOCK and MMC_READ_MULTIPLE_BLOCKS with just one block. > >> If so, then that should probably be mentioned in a comment somewhere. > >> > > > > There are hosts out there (Atmel AT91-based) which need to know if the > > transfer is going to be multiple block. Rather than have them test > > the op-code (which is what they're already doing), we provide a flag > > instead. > > As far as the hardware is concerned there are two "multi-block" transfers: > > * Multiple, back-to-back blocks. > * One or more blocks that need to be terminated by some form of stop > command. > > The first can be identified by checking the number of blocks in the > request, the latter is harder to identify since it's a protocol semantic > (it could be just one block, but still need a stop). Does MMC_DATA_MULTI > indicate the latter, former or both?
In short, it's defined to be whatever AT91_MCI_TRTYP_MULTIPLE means in the AT91RM9200 MMC host driver, which appears to be set for any of the multiple block commands. They currently are doing:
+static const u32 commands[64] = { + /* Class 1 (0) */ + MMC_GO_IDLE_STATE, + MMC_SEND_OP_COND | AT91_MCI_RSPTYP_48, + MMC_ALL_SEND_CID | AT91_MCI_RSPTYP_136, + MMC_SET_RELATIVE_ADDR | AT91_MCI_RSPTYP_48 | AT91_MCI_MAXLAT, + MMC_SET_DSR | AT91_MCI_MAXLAT, ... + MMC_READ_SINGLE_BLOCK | AT91_MCI_RSPTYP_48 | AT91_MCI_MAXLAT | AT91_MCI_TRDIR | AT91_MCI_TRCMD_START | AT91_MCI_TRTYP_BLOCK, + MMC_READ_MULTIPLE_BLOCK | AT91_MCI_RSPTYP_48 | AT91_MCI_MAXLAT | AT91_MCI_TRDIR | AT91_MCI_TRCMD_START | AT91_MCI_TRTYP_MULTIPLE, ... + MMC_WRITE_BLOCK | AT91_MCI_RSPTYP_48 | AT91_MCI_MAXLAT | AT91_MCI_TRCMD_START | AT91_MCI_TRTYP_BLOCK, + MMC_WRITE_MULTIPLE_BLOCK| AT91_MCI_RSPTYP_48 | AT91_MCI_MAXLAT | AT91_MCI_TRCMD_START | AT91_MCI_TRTYP_MULTIPLE,
and using that as a lookup table by command for the value to put into the command register. I want to eliminate that, and not passing the MULTI flag prevents elimination of this table.
-- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: 2.6 Serial core - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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