From f03946210d67be9a33ad63f6a0eed7cdf8c28334 Mon Sep 17 00:00:00 2001 From: Ondrej Zary Date: Sun, 3 Jan 2016 16:06:14 +1100 Subject: [PATCH] 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 Signed-off-by: Finn Thain Reviewed-by: Hannes Reinecke Signed-off-by: Martin K. Petersen --- 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 cd79ef402d7a..454b565c0417 100644 --- 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; } -- 2.20.1