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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 951E8E6F082 for ; Tue, 23 Dec 2025 10:41:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=o4OaBidmbSW4mYe98RLfU23Zy3B0zBlZ4itsDmUinHk=; b=a638ofJN25LMqw0CfRgdgGvSJb SwfrDHiFgwPHUxDVzpRimRazk3tOvrH4qQyVUqq7ruwHShg1K10xsfAEzorXT2DCccLzf2/PxOj3H gWbG/Fjmb475IRcLINNmfqhb3xUheLE1b7d0Ndqgo9Di9vsUKASWUNpjS6rKatpKo8AE9DQfVX1LB wM9XUKENFL5b/t8WRkhQEB2IUNvkhIsm2ln9dVure9j9MfDaZxH7GJnueaeDdd1KEwUbstUm+0cWj dIR+gVLPJRDQm9s3IyJoJMFkA9xZEGFnuou5s3AL0kYh9v0nLG15TY+eTSU9XQ4OGQNvW81C6wFgy 4/jeruEg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vXzpv-0000000EtpE-0khY; Tue, 23 Dec 2025 10:41:51 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vXzps-0000000Etov-3jip; Tue, 23 Dec 2025 10:41:49 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id BA5B4600AE; Tue, 23 Dec 2025 10:41:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B8EA8C113D0; Tue, 23 Dec 2025 10:41:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1766486507; bh=dh1LliqkmgcxlRpXE4EKf7TKTcpUvkSiqOpQkRgrNGg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ehXOHZRH3fe4YvnWKEw6pTVW2pbWT5bBgiBswCQP+mCqQuswq1dDSeRBBW6rQPwsc dVR1KzAR1jQesyvFk2/8iKqEUA7IRQyq0Aqaiuv3B8arbU7hB1ECpNxYlOaw2stzMd 5YdxjHkHMOUeEM4UnXoM/CtL49zQg4f0CE9rmQNeeeNs2eh7Y9NiquWHtPs/zHDs/9 DuVhdm3T7PaXeCoFR+P48FnRL2KNsRcoAyGDS2yEiGrkxHtQA+5V0vnDIWFgMjBVfb dihF+oI+uNHyjra+sM2iijAVYTDaHzpPf8w+oAXzEtzismq6MbeLlFQciymiYGglzd RH7lvTqmlUMPQ== Date: Tue, 23 Dec 2025 16:11:43 +0530 From: Vinod Koul To: Frank Li Cc: Manivannan Sadhasivam , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , Kishon Vijay Abraham I , Bjorn Helgaas , Christoph Hellwig , Sagi Grimberg , Chaitanya Kulkarni , Herbert Xu , "David S. Miller" , Nicolas Ferre , Alexandre Belloni , Claudiu Beznea , Koichiro Den , Niklas Cassel , dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linux-nvme@lists.infradead.org, mhi@lists.linux.dev, linux-arm-msm@vger.kernel.org, linux-crypto@vger.kernel.org, linux-arm-kernel@lists.infradead.org, imx@lists.linux.dev Subject: Re: [PATCH v2 1/8] dmaengine: Add API to combine configuration and preparation (sg and single) Message-ID: References: <20251218-dma_prep_config-v2-0-c07079836128@nxp.com> <20251218-dma_prep_config-v2-1-c07079836128@nxp.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251218-dma_prep_config-v2-1-c07079836128@nxp.com> X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On 18-12-25, 10:56, Frank Li wrote: > Previously, configuration and preparation required two separate calls. This > works well when configuration is done only once during initialization. > > However, in cases where the burst length or source/destination address must > be adjusted for each transfer, calling two functions is verbose and > requires additional locking to ensure both steps complete atomically. > > Add a new API dmaengine_prep_config_single() and dmaengine_prep_config_sg() > and callback device_prep_config_sg() that combines configuration and > preparation into a single operation. If the configuration argument is > passed as NULL, fall back to the existing implementation. > > Add a new API dmaengine_prep_config_single_safe() and > dmaengine_prep_config_sg_safe() for re-entrancy, which require driver > implement callback device_prep_config_sg(). > > Tested-by: Niklas Cassel > Signed-off-by: Frank Li > --- > change in v2 > - add () for function > - use short name device_prep_sg(), remove "slave" and "config". the 'slave' > is reduntant. after remove slave, the function name is difference existed > one, so remove _config suffix. > --- > Documentation/driver-api/dmaengine/client.rst | 9 +++ > include/linux/dmaengine.h | 103 ++++++++++++++++++++++++-- > 2 files changed, 105 insertions(+), 7 deletions(-) > > diff --git a/Documentation/driver-api/dmaengine/client.rst b/Documentation/driver-api/dmaengine/client.rst > index d491e385d61a98b8a804cd823caf254a2dc62cf4..02c45b7d7a779421411eb9c68325cdedafcfe3b1 100644 > --- a/Documentation/driver-api/dmaengine/client.rst > +++ b/Documentation/driver-api/dmaengine/client.rst > @@ -80,6 +80,10 @@ The details of these operations are: > > - slave_sg: DMA a list of scatter gather buffers from/to a peripheral > > + - config_sg: Similar with slave_sg, just pass down dma_slave_config > + struct to avoid call dmaengine_slave_config() every time if need > + adjust burst length or FIFO address. > + > - peripheral_dma_vec: DMA an array of scatter gather buffers from/to a > peripheral. Similar to slave_sg, but uses an array of dma_vec > structures instead of a scatterlist. > @@ -106,6 +110,11 @@ The details of these operations are: > unsigned int sg_len, enum dma_data_direction direction, > unsigned long flags); > > + struct dma_async_tx_descriptor *dmaengine_prep_config_sg( > + struct dma_chan *chan, struct scatterlist *sgl, > + unsigned int sg_len, enum dma_transfer_direction dir, > + unsigned long flags, struct dma_slave_config *config); > + > struct dma_async_tx_descriptor *dmaengine_prep_peripheral_dma_vec( > struct dma_chan *chan, const struct dma_vec *vecs, > size_t nents, enum dma_data_direction direction, > diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h > index 99efe2b9b4ea9844ca6161208362ef18ef111d96..276dca760f95e1131f5ff5bf69752c4c9cb1bcad 100644 > --- a/include/linux/dmaengine.h > +++ b/include/linux/dmaengine.h > @@ -835,6 +835,8 @@ struct dma_filter { > * where the address and size of each segment is located in one entry of > * the dma_vec array. > * @device_prep_slave_sg: prepares a slave dma operation > + * (Deprecated, use @device_prep_config_sg) Sorry that is _not_ deprecated, we are adding another way to do this in a single shot > + * @device_prep_config_sg: prepares a slave DMA operation with dma_slave_config > * @device_prep_dma_cyclic: prepare a cyclic dma operation suitable for audio. > * The function takes a buffer of size buf_len. The callback function will > * be called after period_len bytes have been transferred. > @@ -934,6 +936,11 @@ struct dma_device { > struct dma_chan *chan, struct scatterlist *sgl, > unsigned int sg_len, enum dma_transfer_direction direction, > unsigned long flags, void *context); > + struct dma_async_tx_descriptor *(*device_prep_config_sg)( > + struct dma_chan *chan, struct scatterlist *sgl, > + unsigned int sg_len, enum dma_transfer_direction direction, > + unsigned long flags, struct dma_slave_config *config, > + void *context); > struct dma_async_tx_descriptor *(*device_prep_dma_cyclic)( > struct dma_chan *chan, dma_addr_t buf_addr, size_t buf_len, > size_t period_len, enum dma_transfer_direction direction, > @@ -974,22 +981,85 @@ static inline bool is_slave_direction(enum dma_transfer_direction direction) > (direction == DMA_DEV_TO_DEV); > } > > -static inline struct dma_async_tx_descriptor *dmaengine_prep_slave_single( > - struct dma_chan *chan, dma_addr_t buf, size_t len, > - enum dma_transfer_direction dir, unsigned long flags) > +/* > + * Re-entrancy and locking considerations for callers: > + * > + * dmaengine_prep_config_single(sg)_safe() is re-entrant and requires the > + * DMA engine driver to implement device_prep_config_sg(). It returns NULL > + * if device_prep_config_sg() is not implemented. > + * > + * The unsafe variant (without the _safe suffix) falls back to calling > + * dmaengine_slave_config() and dmaengine_prep_slave_sg() separately. > + * In this case, additional locking may be required, depending on the > + * DMA consumer's usage. > + */ > +static inline struct dma_async_tx_descriptor * > +dmaengine_prep_config_sg_safe(struct dma_chan *chan, struct scatterlist *sgl, > + unsigned int sg_len, enum dma_transfer_direction dir, > + unsigned long flags, struct dma_slave_config *config) > +{ > + if (!chan || !chan->device || !chan->device->device_prep_config_sg) > + return NULL; > + > + return chan->device->device_prep_config_sg(chan, sgl, sg_len, > + dir, flags, config, NULL); > +} > + > +static inline struct dma_async_tx_descriptor * > +dmaengine_prep_config_single_safe(struct dma_chan *chan, dma_addr_t buf, > + size_t len, enum dma_transfer_direction dir, unsigned long flags, > + struct dma_slave_config *config) Agree with Damien, this could look better! -- ~Vinod