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Subject[PATCH 72/71] ncr5380: Fix pseudo-DMA
Date
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>
---
drivers/scsi/g_NCR5380.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/scsi/g_NCR5380.c b/drivers/scsi/g_NCR5380.c
index 0daffe2..a9a237f 100644
--- a/drivers/scsi/g_NCR5380.c
+++ b/drivers/scsi/g_NCR5380.c
@@ -703,6 +703,10 @@ 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;
}

--
Ondrej Zary


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