From dde2020754aeb14e17052d61784dcb37f252aac2 Mon Sep 17 00:00:00 2001 From: James Bottomley Date: Tue, 19 Feb 2008 11:36:56 +0100 Subject: libata: eliminate the home grown dma padding in favour of that provided by the block layer ATA requires that all DMA transfers begin and end on word boundaries. Because of this, a large amount of machinery grew up in ide to adjust scatterlists on this basis. However, as of 2.5, the block layer has a dma_alignment variable which ensures both the beginning and length of a DMA transfer are aligned on the dma_alignment boundary. Although the block layer does adjust the beginning of the transfer to ensure this happens, it doesn't actually adjust the length, it merely makes sure that space is allocated for transfers beyond the declared length. The upshot of this is that scatterlists may be padded to any size between the actual length and the length adjusted to the dma_alignment safely knowing that memory is allocated in this region. Right at the moment, SCSI takes the default dma_aligment which is on a 512 byte boundary. Note that this aligment only applies to transfers coming in from user space. However, since all kernel allocations are automatically aligned on a minimum of 32 byte boundaries, it is safe to adjust them in this manner as well. tj: * Adjusting sg after padding is done in block layer. Make libata set queue alignment correctly for ATAPI devices and drop broken sg mangling from ata_sg_setup(). * Use request->raw_data_len for ATAPI transfer chunk size. * Killed qc->raw_nbytes. * Separated out killing qc->n_iter. Signed-off-by: James Bottomley Signed-off-by: Tejun Heo Signed-off-by: Jens Axboe --- drivers/ata/libata-scsi.c | 23 ++++++----------------- 1 file changed, 6 insertions(+), 17 deletions(-) (limited to 'drivers/ata/libata-scsi.c') diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c index 1cea18f62abc..6e15c5ddae6d 100644 --- a/drivers/ata/libata-scsi.c +++ b/drivers/ata/libata-scsi.c @@ -832,24 +832,16 @@ static void ata_scsi_dev_config(struct scsi_device *sdev, /* configure max sectors */ blk_queue_max_sectors(sdev->request_queue, dev->max_sectors); - /* SATA DMA transfers must be multiples of 4 byte, so - * we need to pad ATAPI transfers using an extra sg. - * Decrement max hw segments accordingly. - */ - if (dev->class == ATA_DEV_ATAPI) { - struct request_queue *q = sdev->request_queue; - blk_queue_max_hw_segments(q, q->max_hw_segments - 1); - + if (dev->class == ATA_DEV_ATAPI) /* set the min alignment */ blk_queue_update_dma_alignment(sdev->request_queue, ATA_DMA_PAD_SZ - 1); - } else + else { /* ATA devices must be sector aligned */ blk_queue_update_dma_alignment(sdev->request_queue, ATA_SECT_SIZE - 1); - - if (dev->class == ATA_DEV_ATA) sdev->manage_start_stop = 1; + } if (dev->flags & ATA_DFLAG_AN) set_bit(SDEV_EVT_MEDIA_CHANGE, sdev->supported_events); @@ -2500,7 +2492,7 @@ static unsigned int atapi_xlat(struct ata_queued_cmd *qc) * want to set it properly, and for DMA where it is * effectively meaningless. */ - nbytes = min(qc->nbytes, (unsigned int)63 * 1024); + nbytes = min(scmd->request->raw_data_len, (unsigned int)63 * 1024); /* Most ATAPI devices which honor transfer chunk size don't * behave according to the spec when odd chunk size which @@ -3555,7 +3547,7 @@ EXPORT_SYMBOL_GPL(ata_sas_port_alloc); * @ap: Port to initialize * * Called just after data structures for each port are - * initialized. Allocates DMA pad. + * initialized. * * May be used as the port_start() entry in ata_port_operations. * @@ -3564,7 +3556,7 @@ EXPORT_SYMBOL_GPL(ata_sas_port_alloc); */ int ata_sas_port_start(struct ata_port *ap) { - return ata_pad_alloc(ap, ap->dev); + return 0; } EXPORT_SYMBOL_GPL(ata_sas_port_start); @@ -3572,8 +3564,6 @@ EXPORT_SYMBOL_GPL(ata_sas_port_start); * ata_port_stop - Undo ata_sas_port_start() * @ap: Port to shut down * - * Frees the DMA pad. - * * May be used as the port_stop() entry in ata_port_operations. * * LOCKING: @@ -3582,7 +3572,6 @@ EXPORT_SYMBOL_GPL(ata_sas_port_start); void ata_sas_port_stop(struct ata_port *ap) { - ata_pad_free(ap, ap->dev); } EXPORT_SYMBOL_GPL(ata_sas_port_stop); -- cgit v1.2.2