From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753846Ab1HAJl0 (ORCPT ); Mon, 1 Aug 2011 05:41:26 -0400 Received: from eu1sys200aog114.obsmtp.com ([207.126.144.137]:40026 "EHLO eu1sys200aog114.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753701Ab1HAJj4 (ORCPT ); Mon, 1 Aug 2011 05:39:56 -0400 From: Viresh Kumar To: Cc: , , , , , , , , , , , , , , , Subject: [PATCH V2 15/20] dmaengine/amba-pl08x: Align lli_len to max(src.width, dst.width) Date: Mon, 1 Aug 2011 15:07:25 +0530 Message-ID: X-Mailer: git-send-email 1.7.2.2 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently lli_len is aligned to min of two widths, which looks to be incorrect. Instead it should be aligned to max of both widths. Lets say, total_size = 441 bytes MIN: lets check if min() suits or not: CASE 1: srcwidth = 1, dstwidth = 4 min(src, dst) = 1 i.e. We program transfer size in control reg to 441. Now, till 440 bytes everything is fine, but on the last byte DMAC can't transfer 1 byte to dst, as its width is 4. CASE 2: srcwidth = 4, dstwidth = 1 min(src, dst) = 1 i.e. we program transfer size in control reg to 110 (data transferred = 110 * srcwidth). So, here too 1 byte is left, but on the source side. MAX: Lets check if max() suits or not: CASE 3: srcwidth = 1, dstwidth = 4 max(src, dst) = 4 Aligned size is 440 i.e. We program transfer size in control reg to 440. Now, all 440 bytes will be transferred without any issues. CASE 4: srcwidth = 4, dstwidth = 1 max(src, dst) = 4 Aligned size is 440 i.e. We program transfer size in control reg to 110 (data transferred = 110 * srcwidth). Now, also all 440 bytes will be transferred without any issues. Signed-off-by: Viresh Kumar Acked-by: Linus Walleij --- drivers/dma/amba-pl08x.c | 12 +++++++----- 1 files changed, 7 insertions(+), 5 deletions(-) diff --git a/drivers/dma/amba-pl08x.c b/drivers/dma/amba-pl08x.c index 0bdf3b8..ef02fb9 100644 --- a/drivers/dma/amba-pl08x.c +++ b/drivers/dma/amba-pl08x.c @@ -666,20 +666,22 @@ static int pl08x_fill_llis_for_desc(struct pl08x_driver_data *pl08x, * width left */ while (bd.remainder > (mbus->buswidth - 1)) { - size_t lli_len, tsize; + size_t lli_len, tsize, width; /* * If enough left try to send max possible, * otherwise try to send the remainder */ lli_len = min(bd.remainder, max_bytes_per_lli); + /* - * Check against minimum bus alignment: Calculate actual + * Check against maximum bus alignment: Calculate actual * transfer size in relation to bus width and get a - * maximum remainder of the smallest bus width - 1 + * maximum remainder of the highest bus width - 1 */ - tsize = lli_len / min(mbus->buswidth, sbus->buswidth); - lli_len = tsize * min(mbus->buswidth, sbus->buswidth); + width = max(mbus->buswidth, sbus->buswidth); + lli_len = (lli_len / width) * width; + tsize = lli_len / bd.srcbus.buswidth; dev_vdbg(&pl08x->adev->dev, "%s fill lli with single lli chunk of " -- 1.7.2.2