From mboxrd@z Thu Jan 1 00:00:00 1970 From: Finn Thain Subject: [PATCH v3 72/77] ncr5380: Fix pseudo DMA transfers on 53C400 Date: Tue, 22 Dec 2015 12:18:50 +1100 Message-ID: <20151222011757.605771566@telegraphics.com.au> References: <20151222011737.980475848@telegraphics.com.au> Return-path: Content-Disposition: inline; filename=72-71 Sender: linux-kernel-owner@vger.kernel.org To: "James E.J. Bottomley" , Michael Schmitz , linux-m68k@vger.kernel.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, "Martin K. Petersen" Cc: Ondrej Zary List-Id: linux-m68k@vger.kernel.org From: Ondrej Zary 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 --- drivers/scsi/g_NCR5380.c | 4 ++++ 1 file changed, 4 insertions(+) Index: linux/drivers/scsi/g_NCR5380.c =================================================================== --- linux.orig/drivers/scsi/g_NCR5380.c 2015-12-22 12:17:15.000000000 +1100 +++ linux/drivers/scsi/g_NCR5380.c 2015-12-22 12:17:27.000000000 +1100 @@ -702,6 +702,10 @@ static int generic_NCR5380_dma_xfer_len( !(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; }