In theory this isn't needed. In practice it seems to matter now and then
and was also done by the old IDE DMA layer.
Signed-off-by: Alan Cox <alan@xxxxxxxxxx>
diff -u --exclude-from /usr/src/exclude --new-file --recursive linux.vanilla-2.6.23rc6-mm1/drivers/ata/libata-scsi.c linux-2.6.23rc6-mm1/drivers/ata/libata-scsi.c
--- linux.vanilla-2.6.23rc6-mm1/drivers/ata/libata-scsi.c 2007-09-18 15:32:51.000000000 +0100
+++ linux-2.6.23rc6-mm1/drivers/ata/libata-scsi.c 2007-09-19 21:30:51.368961456 +0100
@@ -2276,8 +2276,8 @@
qc->tf.feature |= ATAPI_PKT_DMA;
} else {
qc->tf.protocol = ATA_PROT_ATAPI;
- qc->tf.lbam = (8 * 1024) & 0xff;
- qc->tf.lbah = (8 * 1024) >> 8;
+ qc->tf.lbam = SCSI_SENSE_BUFFERSIZE;
+ qc->tf.lbah = 0;
}
qc->nbytes = SCSI_SENSE_BUFFERSIZE;
@@ -2386,6 +2386,7 @@
struct ata_device *dev = qc->dev;
int using_pio = (dev->flags & ATA_DFLAG_PIO);
int nodata = (scmd->sc_data_direction == DMA_NONE);
+ unsigned int nbytes;
memset(qc->cdb, 0, dev->cdb_len);
memcpy(qc->cdb, scmd->cmnd, scmd->cmd_len);
@@ -2400,19 +2401,25 @@
qc->tf.command = ATA_CMD_PACKET;
qc->nbytes = scmd->request_bufflen;
-
+
/* check whether ATAPI DMA is safe */
if (!using_pio && ata_check_atapi_dma(qc))
using_pio = 1;
+ /* Some controller variants snoop this value for Packet transfers
+ to do state machine and FIFO management. Thus we want to set it
+ properly, and for DMA where it is effectively meaningless */
+ nbytes = min(qc->nbytes, (unsigned int)63 * 1024);
+
+ qc->tf.lbam = (nbytes & 0xFF);
+ qc->tf.lbah = (nbytes >> 8);
+
if (using_pio || nodata) {
/* no data, or PIO data xfer */
if (nodata)
qc->tf.protocol = ATA_PROT_ATAPI_NODATA;
else
qc->tf.protocol = ATA_PROT_ATAPI;
- qc->tf.lbam = (8 * 1024) & 0xff;
- qc->tf.lbah = (8 * 1024) >> 8;
} else {
/* DMA data xfer */
qc->tf.protocol = ATA_PROT_ATAPI_DMA;
@@ -2423,6 +2430,9 @@
qc->tf.feature |= ATAPI_DMADIR;
}
+
+ /* FIXME: We need to translate 0x05 READ_BLOCK_LIMITS to a MODE_SENSE
+ as ATAPI tape drives don't get this right otherwise */
return 0;
}
-
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