libata-sff: clean up BMDMA initialization

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
    ata_sff_post_internal_cmd()).

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
  ata_bmdma_port_start32().

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: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 3 insertions, 6 deletions

diff --git a/include/linux/libata.h b/include/linux/libata.h
index d735728873b5..45a547e42d47 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -1000,7 +1000,6 @@ extern unsigned long ata_xfer_mode2mask(u8 xfer_mode);
 extern int ata_xfer_mode2shift(unsigned long xfer_mode);
 extern const char *ata_mode_string(unsigned long xfer_mask);
 extern unsigned long ata_id_xfermask(const u16 *id);
-extern int ata_port_start(struct ata_port *ap);
 extern int ata_std_qc_defer(struct ata_queued_cmd *qc);
 extern void ata_noop_qc_prep(struct ata_queued_cmd *qc);
 extern void ata_sg_init(struct ata_queued_cmd *qc, struct scatterlist *sg,
@@ -1616,8 +1615,6 @@ extern void ata_sff_postreset(struct ata_link *link, unsigned int *classes);
 extern void ata_sff_drain_fifo(struct ata_queued_cmd *qc);
 extern void ata_sff_error_handler(struct ata_port *ap);
 extern void ata_sff_post_internal_cmd(struct ata_queued_cmd *qc);
-extern int ata_sff_port_start(struct ata_port *ap);
-extern int ata_sff_port_start32(struct ata_port *ap);
 extern void ata_sff_std_ports(struct ata_ioports *ioaddr);
 #ifdef CONFIG_PCI
 extern int ata_pci_sff_init_host(struct ata_host *host);
@@ -1632,16 +1629,16 @@ extern int ata_pci_sff_init_one(struct pci_dev *pdev,
                 struct scsi_host_template *sht, void *host_priv, int hflags);
 #endif /* CONFIG_PCI */
 
-extern unsigned long ata_bmdma_mode_filter(struct ata_device *dev,
-                                           unsigned long xfer_mask);
 extern void ata_bmdma_setup(struct ata_queued_cmd *qc);
 extern void ata_bmdma_start(struct ata_queued_cmd *qc);
 extern void ata_bmdma_stop(struct ata_queued_cmd *qc);
 extern u8 ata_bmdma_status(struct ata_port *ap);
+extern int ata_bmdma_port_start(struct ata_port *ap);
+extern int ata_bmdma_port_start32(struct ata_port *ap);
 
 #ifdef CONFIG_PCI
 extern int ata_pci_bmdma_clear_simplex(struct pci_dev *pdev);
-extern int ata_pci_bmdma_init(struct ata_host *host);
+extern void ata_pci_bmdma_init(struct ata_host *host);
 #endif /* CONFIG_PCI */
 
 /**