From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DC3F7ECDE5F for ; Mon, 23 Jul 2018 10:54:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 884CF20854 for ; Mon, 23 Jul 2018 10:54:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 884CF20854 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=pengutronix.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387937AbeGWLy7 (ORCPT ); Mon, 23 Jul 2018 07:54:59 -0400 Received: from metis.ext.pengutronix.de ([85.220.165.71]:33395 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387830AbeGWLy7 (ORCPT ); Mon, 23 Jul 2018 07:54:59 -0400 Received: from kresse.hi.pengutronix.de ([2001:67c:670:100:1d::2a]) by metis.ext.pengutronix.de with esmtp (Exim 4.89) (envelope-from ) id 1fhYTm-0002BQ-Hy; Mon, 23 Jul 2018 12:54:14 +0200 Message-ID: <1532343252.3163.99.camel@pengutronix.de> Subject: Re: [PATCH v3 3/3] dmaengine: imx-sdma: allocate max 20 bds for one transfer From: Lucas Stach To: Robin Gong , vkoul@kernel.org, dan.j.williams@intel.com, s.hauer@pengutronix.de, linux@armlinux.org.uk Cc: dmaengine@vger.kernel.org, linux-imx@nxp.com, kernel@pengutronix.de, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Date: Mon, 23 Jul 2018 12:54:12 +0200 In-Reply-To: <1532367972-29707-4-git-send-email-yibin.gong@nxp.com> References: <1532367972-29707-1-git-send-email-yibin.gong@nxp.com> <1532367972-29707-4-git-send-email-yibin.gong@nxp.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6-1+deb9u1 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::2a X-SA-Exim-Mail-From: l.stach@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am Dienstag, den 24.07.2018, 01:46 +0800 schrieb Robin Gong: > If multi-bds used in one transfer, all bds should be consisten > memory.To easily follow it, enlarge the dma pool size into 20 bds, > and it will report error if the number of bds is over than 20. For > dmatest, the max count for single transfer is NUM_BD * > SDMA_BD_MAX_CNT = 20 * 65535 = ~1.28MB. Both the commit message and the comment need a lot more care to actually tell what this commit is trying to achieve. Currently I don't follow at all. What does "consisten" mean? Do you mean BDs should be contiguous in memory? What do you gain by over-allocating each BD by a factor of 20? Regards, Lucas > Signed-off-by: Robin Gong > --- >  drivers/dma/imx-sdma.c | 17 ++++++++++++++++- >  1 file changed, 16 insertions(+), 1 deletion(-) > > diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c > index b4ec2d2..5973489 100644 > --- a/drivers/dma/imx-sdma.c > +++ b/drivers/dma/imx-sdma.c > @@ -298,6 +298,15 @@ struct sdma_context_data { > >   u32  scratch7; >  } __attribute__ ((packed)); >   > +/* > + * All bds in one transfer should be consitent on SDMA. To easily follow it,just > + * set the dma pool size as the enough bds. For example, in dmatest case, the > + * max 20 bds means the max for single transfer is NUM_BD * SDMA_BD_MAX_CNT = 20 > + * * 65535 = ~1.28MB. 20 bds supposed to be enough basically.If it's still not > + * enough in some specific cases, enlarge it here.Warning message would also > + * appear if the bd numbers is over than 20. > + */ > +#define NUM_BD 20 >   >  struct sdma_engine; >   > @@ -1273,7 +1282,7 @@ static int sdma_alloc_chan_resources(struct dma_chan *chan) > >   goto disable_clk_ahb; >   > >   sdmac->bd_pool = dma_pool_create("bd_pool", chan->device->dev, > > - sizeof(struct sdma_buffer_descriptor), > > + NUM_BD * sizeof(struct sdma_buffer_descriptor), > >   32, 0); >   > >   return 0; > @@ -1314,6 +1323,12 @@ static struct sdma_desc *sdma_transfer_init(struct sdma_channel *sdmac, >  { > >   struct sdma_desc *desc; >   > > + if (bds > NUM_BD) { > > + dev_err(sdmac->sdma->dev, "%d bds exceed the max %d\n", > > + bds, NUM_BD); > > + goto err_out; > > + } > + > >   desc = kzalloc((sizeof(*desc)), GFP_NOWAIT); > >   if (!desc) > >   goto err_out;