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=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 78C39C433E9 for ; Mon, 21 Dec 2020 09:50:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4A24522CAE for ; Mon, 21 Dec 2020 09:50:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726321AbgLUJs6 (ORCPT ); Mon, 21 Dec 2020 04:48:58 -0500 Received: from mail.kernel.org ([198.145.29.99]:37294 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727333AbgLUJr5 (ORCPT ); Mon, 21 Dec 2020 04:47:57 -0500 Date: Mon, 21 Dec 2020 14:53:55 +0530 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1608542640; bh=JO4ab5ou5wn2IYemAu40S3kxk97Cbr2moLnttUGZi3k=; h=From:To:Cc:Subject:References:In-Reply-To:From; b=OliryD7qqLmTqyoCTX6dzKbEVI2tjG+ledbsd0RWvXKG8A/KHGORZlnpNDKWkv0Wg 9ECU3LxcuWvxzrUcVc7REh/qTu1UGETQSsCOa8Ii2YUXE8Xez/WK/nw7esWPl9Vq7j VVPm4txLNd/Xn/u+tT+WUE6Y3ByL4N+a3JhJBrNGs2yROsTuhaBFGu/XfzJMWvok7i sc0qmk+08Asn6kgIJ4wudG9n2URG9y/tDJKJgFZK6mUD5RRuJP2xGLZYWNFTWnzi77 pSUgqMmMJZ36iRCOfqfusv7qq+21JEJTvchTilRnH8iAn8yhE3xHEX7XafyKloTPCq uwkgSKJRNoHsQ== From: Vinod Koul To: Md Sadre Alam Cc: corbet@lwn.net, agross@kernel.org, bjorn.andersson@linaro.org, dan.j.williams@intel.com, dmaengine@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, sricharan@codeaurora.org Subject: Re: [PATCH] dmaengine: qcom: bam_dma: Add LOCK and UNLOCK flag bit support Message-ID: <20201221092355.GA3323@vkoul-mobl> References: <1608215842-15381-1-git-send-email-mdalam@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1608215842-15381-1-git-send-email-mdalam@codeaurora.org> Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org Hello, On 17-12-20, 20:07, Md Sadre Alam wrote: > This change will add support for LOCK & UNLOCK flag bit support > on CMD descriptor. > > If DMA_PREP_LOCK flag passed in prep_slave_sg then requester of this > transaction wanted to lock the DMA controller for this transaction so > BAM driver should set LOCK bit for the HW descriptor. > > If DMA_PREP_UNLOCK flag passed in prep_slave_sg then requester of this > transaction wanted to unlock the DMA controller.so BAM driver should set > UNLOCK bit for the HW descriptor. Can you explain why would we need to first lock and then unlock..? How would this be used in real world. I have read a bit of documentation but is unclear to me. Also should this be exposed as an API to users, sounds like internal to driver..? > > Signed-off-by: Md Sadre Alam > --- > Documentation/driver-api/dmaengine/provider.rst | 9 +++++++++ > drivers/dma/qcom/bam_dma.c | 9 +++++++++ > include/linux/dmaengine.h | 5 +++++ > 3 files changed, 23 insertions(+) > > diff --git a/Documentation/driver-api/dmaengine/provider.rst b/Documentation/driver-api/dmaengine/provider.rst > index ddb0a81..d7516e2 100644 > --- a/Documentation/driver-api/dmaengine/provider.rst > +++ b/Documentation/driver-api/dmaengine/provider.rst > @@ -599,6 +599,15 @@ DMA_CTRL_REUSE > - This flag is only supported if the channel reports the DMA_LOAD_EOT > capability. > > +- DMA_PREP_LOCK > + > + - If set , the client driver tells DMA controller I am locking you for > + this transcation. > + > +- DMA_PREP_UNLOCK > + > + - If set, the client driver will tells DMA controller I am releasing the lock > + > General Design Notes > ==================== > > diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c > index 4eeb8bb..cdbe395 100644 > --- a/drivers/dma/qcom/bam_dma.c > +++ b/drivers/dma/qcom/bam_dma.c > @@ -58,6 +58,8 @@ struct bam_desc_hw { > #define DESC_FLAG_EOB BIT(13) > #define DESC_FLAG_NWD BIT(12) > #define DESC_FLAG_CMD BIT(11) > +#define DESC_FLAG_LOCK BIT(10) > +#define DESC_FLAG_UNLOCK BIT(9) > > struct bam_async_desc { > struct virt_dma_desc vd; > @@ -644,6 +646,13 @@ static struct dma_async_tx_descriptor *bam_prep_slave_sg(struct dma_chan *chan, > > /* fill in temporary descriptors */ > desc = async_desc->desc; > + if (flags & DMA_PREP_CMD) { > + if (flags & DMA_PREP_LOCK) > + desc->flags |= cpu_to_le16(DESC_FLAG_LOCK); > + if (flags & DMA_PREP_UNLOCK) > + desc->flags |= cpu_to_le16(DESC_FLAG_UNLOCK); > + } > + > for_each_sg(sgl, sg, sg_len, i) { > unsigned int remainder = sg_dma_len(sg); > unsigned int curr_offset = 0; > diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h > index dd357a7..79ccadb4 100644 > --- a/include/linux/dmaengine.h > +++ b/include/linux/dmaengine.h > @@ -190,6 +190,9 @@ struct dma_interleaved_template { > * transaction is marked with DMA_PREP_REPEAT will cause the new transaction > * to never be processed and stay in the issued queue forever. The flag is > * ignored if the previous transaction is not a repeated transaction. > + * @DMA_PREP_LOCK: tell the driver that DMA HW engine going to be locked for this > + * transaction , until not seen DMA_PREP_UNLOCK flag set. > + * @DMA_PREP_UNLOCK: tell the driver to unlock the DMA HW engine. > */ > enum dma_ctrl_flags { > DMA_PREP_INTERRUPT = (1 << 0), > @@ -202,6 +205,8 @@ enum dma_ctrl_flags { > DMA_PREP_CMD = (1 << 7), > DMA_PREP_REPEAT = (1 << 8), > DMA_PREP_LOAD_EOT = (1 << 9), > + DMA_PREP_LOCK = (1 << 10), > + DMA_PREP_UNLOCK = (1 << 11), > }; > > /** > -- > 2.7.4 -- ~Vinod