• Tejun Heo's avatar
    libata-sff: clean up BMDMA initialization · c7087652
    Tejun Heo authored
    When BMDMA initialization failed or BMDMA was not available for
    whatever reason, bmdma_addr was left at zero and used as an indication
    that BMDMA shouldn't be used.  This leads to the following problems.
    p1. For BMDMA drivers which don't use traditional BMDMA register,
        ata_bmdma_mode_filter() incorrectly inhibits DMA modes.  Those
        drivers either have to inherit from ata_sff_port_ops or clear
        ->mode_filter explicitly.
    p2. non-BMDMA drivers call into BMDMA PRD table allocation.  It
        doesn't actually allocate PRD table if bmdma_addr is not
        initialized but is still confusing.
    p3. For BMDMA drivers which don't use traditional BMDMA register, some
        methods might not be invoked as expected (e.g. bmdma_stop from
    p4. SFF drivers w/ custom DMA interface implement noop BMDMA ops
        worrying libata core might call into one of them.
    These problems are caused by the muddy line between SFF and BMDMA and
    the assumption that all BMDMA controllers initialize bmdma_addr.
    This patch fixes p1 and p2 by removing the bmdma_addr assumption and
    moving prd allocation to BMDMA port start.  Later patches will fix the
    remaining issues.
    This patch improves BMDMA initialization such that
    * When BMDMA register initialization fails, falls back to PIO instead
      of failing.  ata_pci_bmdma_init() never fails now.
    * When ata_pci_bmdma_init() falls back to PIO, it clears
      ap->mwdma_mask and udma_mask instead of depending on
      ata_bmdma_mode_filter().  This makes ata_bmdma_mode_filter()
      unnecessary thus resolving p1.
    * ata_port_start() which actually is BMDMA specific is moved to
      ata_bmdma_port_start().  ata_port_start() and ata_sff_port_start()
      are killed.
    * ata_sff_port_start32() is moved and renamed to
    Drivers which no longer call into PRD table allocation are...
      pdc_adma, sata_inic162x, sata_qstor, sata_sx4, pata_cmd640 and all
      drivers which inherit from ata_sff_port_ops.
    pata_icside sets ->port_start to ATA_OP_NULL as it doesn't need PRD
    but is a BMDMA controller and doesn't have custom port_start like
    other such controllers.
    Note that with the previous patch which makes all and only BMDMA
    drivers inherit from ata_bmdma_port_ops, this change doesn't break
    drivers which need PRD table.
    Signed-off-by: default avatarTejun Heo <tj@kernel.org>
    Signed-off-by: default avatarJeff Garzik <jgarzik@redhat.com>
pata_icside.c 16.1 KB