linux-kernel - Re: [PATCH v3 0/9] dmaengine: Add new API to combine configuration and descriptor preparation

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Message-ID: <aX0EXjM4LlO3Hygd@lizhi-Precision-Tower-5810>
Date: Fri, 30 Jan 2026 14:19:58 -0500
From: Frank Li <Frank.li@....com>
To: Vinod Koul <vkoul@...nel.org>, Manivannan Sadhasivam <mani@...nel.org>,
	Krzysztof Wilczyński <kwilczynski@...nel.org>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>, Christoph Hellwig <hch@....de>,
	Sagi Grimberg <sagi@...mberg.me>,
	Chaitanya Kulkarni <kch@...dia.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	"David S. Miller" <davem@...emloft.net>,
	Nicolas Ferre <nicolas.ferre@...rochip.com>,
	Alexandre Belloni <alexandre.belloni@...tlin.com>,
	Claudiu Beznea <claudiu.beznea@...on.dev>,
	Koichiro Den <den@...inux.co.jp>, Niklas Cassel <cassel@...nel.org>
Cc: dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-nvme@...ts.infradead.org,
	mhi@...ts.linux.dev, linux-arm-msm@...r.kernel.org,
	linux-crypto@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	imx@...ts.linux.dev, Damien Le Moal <dlemoal@...nel.org>
Subject: Re: [PATCH v3 0/9] dmaengine: Add new API to combine configuration
 and descriptor preparation

On Wed, Jan 21, 2026 at 11:30:09AM -0500, Frank Li wrote:
> On Mon, Jan 05, 2026 at 05:46:50PM -0500, 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.
> >
> > 	if (dmaengine_slave_config(chan, &sconf)) {
> > 		dev_err(dev, "DMA slave config fail\n");
> > 		return -EIO;
> > 	}
> >
> > 	tx = dmaengine_prep_slave_single(chan, dma_local, len, dir, flags);
> >
> > After new API added
> >
> > 	tx = dmaengine_prep_config_single(chan, dma_local, len, dir, flags, &sconf);
> >
> > Additional, prevous two calls requires additional locking to ensure both
> > steps complete atomically.
> >
> >     mutex_lock()
> >     dmaengine_slave_config()
> >     dmaengine_prep_slave_single()
> >     mutex_unlock()
> >
> > after new API added, mutex lock can be moved. See patch
> >      nvmet: pci-epf: Use dmaengine_prep_config_single_safe() API
> >
> > Signed-off-by: Frank Li <Frank.Li@....com>
> > ---
>
> Vinod:
> 	Can you take care these patches? At least first 2 patches! So
> I can did more clean up at next kernel release.

Vinod Koul:

	Do you have chance to pick up (at least first 2 patches) for 6.20?
So I can start do more cleanup work.

	There are two serial depend on this one

https://lore.kernel.org/dmaengine/20251212-edma_ll-v1-0-fc863d9f5ca3@nxp.com/
https://lore.kernel.org/dmaengine/aWT4p7RnFykJnuOz@ryzen/

Frank

>
> Frank
>
> > Changes in v3:
> > - collect review tags
> > - create safe version in framework
> > - Link to v2: https://lore.kernel.org/r/20251218-dma_prep_config-v2-0-c07079836128@nxp.com
> >
> > Changes in v2:
> > - Use name dmaengine_prep_config_single() and dmaengine_prep_config_sg()
> > - Add _safe version to avoid confuse, which needn't additional mutex.
> > - Update document/
> > - Update commit message. add () for function name. Use upcase for subject.
> > - Add more explain for remove lock.
> > - Link to v1: https://lore.kernel.org/r/20251208-dma_prep_config-v1-0-53490c5e1e2a@nxp.com
> >
> > ---
> > Frank Li (9):
> >       dmaengine: Add API to combine configuration and preparation (sg and single)
> >       dmaengine: Add safe API to combine configuration and preparation
> >       PCI: endpoint: pci-epf-test: Use dmaenigne_prep_config_single() to simplify code
> >       dmaengine: dw-edma: Use new .device_prep_config_sg() callback
> >       dmaengine: dw-edma: Pass dma_slave_config to dw_edma_device_transfer()
> >       nvmet: pci-epf: Remove unnecessary dmaengine_terminate_sync() on each DMA transfer
> >       nvmet: pci-epf: Use dmaengine_prep_config_single_safe() API
> >       PCI: epf-mhi: Use dmaengine_prep_config_single() to simplify code
> >       crypto: atmel: Use dmaengine_prep_config_single() API
> >
> >  Documentation/driver-api/dmaengine/client.rst |   9 ++
> >  drivers/crypto/atmel-aes.c                    |  10 +--
> >  drivers/dma/dmaengine.c                       |   3 +
> >  drivers/dma/dw-edma/dw-edma-core.c            |  41 ++++++---
> >  drivers/nvme/target/pci-epf.c                 |  21 ++---
> >  drivers/pci/endpoint/functions/pci-epf-mhi.c  |  52 ++++--------
> >  drivers/pci/endpoint/functions/pci-epf-test.c |   8 +-
> >  include/linux/dmaengine.h                     | 117 ++++++++++++++++++++++++--
> >  8 files changed, 177 insertions(+), 84 deletions(-)
> > ---
> > base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
> > change-id: 20251204-dma_prep_config-654170d245a2
> >
> > Best regards,
> > --
> > Frank Li <Frank.Li@....com>
> >