From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752474AbcFUPyz (ORCPT ); Tue, 21 Jun 2016 11:54:55 -0400 Received: from mga09.intel.com ([134.134.136.24]:11209 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752373AbcFUPyx (ORCPT ); Tue, 21 Jun 2016 11:54:53 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.26,504,1459839600"; d="scan'208";a="126056779" Date: Tue, 21 Jun 2016 21:31:39 +0530 From: Vinod Koul To: Jon Hunter Cc: Peter Griffin , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kernel@stlinux.com, linus.walleij@linaro.org, dan.j.williams@intel.com, leoli@freescale.com, zw@zh-kernel.org, baohua@kernel.org, maxime.ripard@free-electrons.com, wens@csie.org, ldewangan@nvidia.com, swarren@wwwdotorg.org, thierry.reding@gmail.com, gnurou@gmail.com, lee.jones@linaro.org, dmaengine@vger.kernel.org, linux-tegra@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH 7/8] dmaengine: tegra20-apb-dma: Only calculate residue if txstate exists. Message-ID: <20160621160139.GC16910@localhost> References: <1465321121-22238-1-git-send-email-peter.griffin@linaro.org> <1465321121-22238-8-git-send-email-peter.griffin@linaro.org> <5757DCAD.1090106@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5757DCAD.1090106@nvidia.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 08, 2016 at 09:51:57AM +0100, Jon Hunter wrote: > Hi Peter, > > On 07/06/16 18:38, Peter Griffin wrote: > > There is no point calculating the residue if there is > > no txstate to store the value. > > > > Signed-off-by: Peter Griffin > > --- > > drivers/dma/tegra20-apb-dma.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c > > index 01e316f..7f4af8c 100644 > > --- a/drivers/dma/tegra20-apb-dma.c > > +++ b/drivers/dma/tegra20-apb-dma.c > > @@ -814,7 +814,7 @@ static enum dma_status tegra_dma_tx_status(struct dma_chan *dc, > > unsigned int residual; > > > > ret = dma_cookie_status(dc, cookie, txstate); > > - if (ret == DMA_COMPLETE) > > + if (ret == DMA_COMPLETE || !txstate) > > return ret; > > Thanks for reporting this. I agree that we should not do this, however, > looking at the code for Tegra, I am wondering if this could change the > actual state that is returned. Looking at dma_cookie_status() it will > call dma_async_is_complete() which will return either DMA_COMPLETE or > DMA_IN_PROGRESS. It could be possible that the actual state for the > DMA transfer in the tegra driver is DMA_ERROR, so I am wondering if we > should do something like the following ... This one is stopping code execution when residue is not valid. Do notice that it check for DMA_COMPLETE OR txstate. In other cases, wit will return 'that' state when txstate is NULL. I am going to apply this. > > diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c > index 01e316f73559..45edab7418d0 100644 > --- a/drivers/dma/tegra20-apb-dma.c > +++ b/drivers/dma/tegra20-apb-dma.c > @@ -822,13 +822,8 @@ static enum dma_status tegra_dma_tx_status(struct dma_chan *dc, > /* Check on wait_ack desc status */ > list_for_each_entry(dma_desc, &tdc->free_dma_desc, node) { > if (dma_desc->txd.cookie == cookie) { > - residual = dma_desc->bytes_requested - > - (dma_desc->bytes_transferred % > - dma_desc->bytes_requested); > - dma_set_residue(txstate, residual); > ret = dma_desc->dma_status; > - spin_unlock_irqrestore(&tdc->lock, flags); > - return ret; > + goto found; > } > } > > @@ -836,17 +831,23 @@ static enum dma_status tegra_dma_tx_status(struct dma_chan *dc, > list_for_each_entry(sg_req, &tdc->pending_sg_req, node) { > dma_desc = sg_req->dma_desc; > if (dma_desc->txd.cookie == cookie) { > - residual = dma_desc->bytes_requested - > - (dma_desc->bytes_transferred % > - dma_desc->bytes_requested); > - dma_set_residue(txstate, residual); > ret = dma_desc->dma_status; > - spin_unlock_irqrestore(&tdc->lock, flags); > - return ret; > + goto found; > } > } > > - dev_dbg(tdc2dev(tdc), "cookie %d does not found\n", cookie); > + dev_warn(tdc2dev(tdc), "cookie %d not found\n", cookie); > + spin_unlock_irqrestore(&tdc->lock, flags); > + return ret; > + > +found: > + if (txstate) { > + residual = dma_desc->bytes_requested - > + (dma_desc->bytes_transferred % > + dma_desc->bytes_requested); > + dma_set_residue(txstate, residual); > + } > + I feel this optimizes stuff, which seems okay. Feel free to send as proper patch. > spin_unlock_irqrestore(&tdc->lock, flags); > return ret; > } > > Cheers > Jon > > -- > nvpublic -- ~Vinod