ncr5380: Fix pseudo DMA transfers on 53C400

Pseudo-DMA (PDMA) has been broken for ages, resulting in hangs on
53C400-based cards.

According to 53C400 datasheet, PDMA transfer length must be a multiple
of 128. Check if that's true and use PIO if it's not.

This makes PDMA work on 53C400 (Canon FG2-5202).

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/g_NCR5380.c b/drivers/scsi/g_NCR5380.c
index cd79ef4..454b565 100644 (file)
--- a/drivers/scsi/g_NCR5380.c
+++ b/drivers/scsi/g_NCR5380.c
@@ -702,6 +702,10 @@ static int generic_NCR5380_dma_xfer_len(struct scsi_cmnd *cmd)
            !(cmd->SCp.this_residual % transfersize))
                transfersize = 32 * 1024;
 
+       /* 53C400 datasheet: non-modulo-128-byte transfers should use PIO */
+       if (transfersize % 128)
+               transfersize = 0;
+
        return transfersize;
 }