From patchwork Mon Jul 29 13:29:54 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Joel Fernandes X-Patchwork-Id: 2834985 Return-Path: X-Original-To: patchwork-linux-omap@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id B2F76C0319 for ; Mon, 29 Jul 2013 13:32:37 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 8B24120212 for ; Mon, 29 Jul 2013 13:32:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 60F5020217 for ; Mon, 29 Jul 2013 13:32:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754294Ab3G2NbA (ORCPT ); Mon, 29 Jul 2013 09:31:00 -0400 Received: from comal.ext.ti.com ([198.47.26.152]:34031 "EHLO comal.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753695Ab3G2Na5 (ORCPT ); Mon, 29 Jul 2013 09:30:57 -0400 Received: from dlelxv90.itg.ti.com ([172.17.2.17]) by comal.ext.ti.com (8.13.7/8.13.7) with ESMTP id r6TDUKYk010731; Mon, 29 Jul 2013 08:30:20 -0500 Received: from DLEE71.ent.ti.com (dlee71.ent.ti.com [157.170.170.114]) by dlelxv90.itg.ti.com (8.14.3/8.13.8) with ESMTP id r6TDUJEl008109; Mon, 29 Jul 2013 08:30:19 -0500 Received: from dlelxv22.itg.ti.com (172.17.1.197) by DLEE71.ent.ti.com (157.170.170.114) with Microsoft SMTP Server id 14.2.342.3; Mon, 29 Jul 2013 08:30:19 -0500 Received: from joel-laptop.itg.ti.com (h0-79.vpn.ti.com [172.24.0.79]) by dlelxv22.itg.ti.com (8.13.8/8.13.8) with ESMTP id r6TDTuP6008221; Mon, 29 Jul 2013 08:30:18 -0500 From: Joel Fernandes To: Tony Lindgren , Sekhar Nori , Santosh Shilimkar , Sricharan R , Rajendra Nayak , Lokesh Vutla , Matt Porter , Grant Likely , Rob Herring , Vinod Koul , Dan Williams , Mark Brown , Benoit Cousson , Russell King , Arnd Bergmann , Olof Johansson , Balaji TK , Gururaja Hebbar , Chris Ball , Jason Kridner CC: Linux OMAP List , Linux ARM Kernel List , Linux DaVinci Kernel List , Linux Kernel Mailing List , Linux MMC List , Joel Fernandes Subject: [PATCH 8/9] dma: edma: Link to dummy slot only for last SG list split Date: Mon, 29 Jul 2013 08:29:54 -0500 Message-ID: <1375104595-16018-9-git-send-email-joelf@ti.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1375104595-16018-1-git-send-email-joelf@ti.com> References: <1375104595-16018-1-git-send-email-joelf@ti.com> MIME-Version: 1.0 Sender: linux-omap-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-omap@vger.kernel.org X-Spam-Status: No, score=-8.4 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Consider the case where we have a scatter-list like: SG1->SG2->SG3->SG4->SG5->SG6->Null For ex, for a MAX_NR_SG of 2, earlier we were splitting this as: SG1->SG2->Null SG3->SG4->Null SG5->SG6->Null Now we split it as SG1->SG2->Null SG3->SG4->Null SG5->SG6->Dummy This approach results in lesser unwanted interrupts that occur for the last list split. The Dummy slot has the property of not raising an error condition if events are missed unlike the Null slot. We are OK with this as we're done with processing the whole list once we reach Dummy. Signed-off-by: Joel Fernandes --- drivers/dma/edma.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/dma/edma.c b/drivers/dma/edma.c index c72e8c9..0d3ebde 100644 --- a/drivers/dma/edma.c +++ b/drivers/dma/edma.c @@ -164,6 +164,12 @@ static void edma_execute(struct edma_chan *echan) edesc->total_processed += total_process; + /* If this is either the last set in a set of SG-list transactions + then setup a link to the dummy slot, this results in all future + events being absorbed and that's OK because we're done */ + if (edesc->total_processed == edesc->pset_nr) + edma_link(echan->slot[total_process-1], echan->ecc->dummy_slot); + edma_resume(echan->ch_num); if (edesc->total_processed <= MAX_NR_SG) {