linux-kernel - Re: [RFC PATCH 0/5] PCIe EPF support for internal DMAC handling and driver update for R-Car PCIe EP to support DMAC

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Date:   Thu, 10 Feb 2022 14:10:52 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Cc:     Kishon Vijay Abraham I <kishon@...com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Marek Vasut <marek.vasut+renesas@...il.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Rob Herring <robh@...nel.org>, linux-pci@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Prabhakar <prabhakar.csengg@...il.com>,
        Biju Das <biju.das.jz@...renesas.com>
Subject: Re: [RFC PATCH 0/5] PCIe EPF support for internal DMAC handling and
 driver update for R-Car PCIe EP to support DMAC

Hi,

On Wed, Jan 26, 2022 at 07:50:38PM +0000, Lad Prabhakar wrote:
> Hi All,
> 
> The current PCIe EPF framework supports DMA data transfers using external
> DMA only, this patch series aims to add support for platforms supporting
> internal DMAC on PCIe for data transfers.
> 
> R-Car PCIe supports internal DMAC to transfer data between Internal Bus to
> PCI Express and vice versa. Last patch fills up the required flags and ops
> to support internal DMAC.
> 
> Patches 1-3 are for PCIe EPF core to support internal DMAC handling, patch
> 4/5 is to fix test cases based on the conversation [1].
> 

This looks similar to the Synopsys eDMA IP [1] that goes with the Synopsys PCIe
endpoint IP. Why can't you represent it as a dmaengine driver and use the
existing DMA support?

Thanks,
Mani

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/dma/dw-edma 

> Patches are based on top of [1] next branch.
> 
> [0] https://www.spinics.net/lists/linux-pci/msg92385.html
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git
> 
> Cheers,
> Prabhakar
> 
> Lad Prabhakar (5):
>   PCI: endpoint: Add ops and flag to support internal DMAC
>   PCI: endpoint: Add support to data transfer using internal dmac
>   misc: pci_endpoint_test: Add driver data for Renesas RZ/G2{EHMN}
>   misc: pci_endpoint_test: Add support to pass flags for buffer
>     allocation
>   PCI: rcar-ep: Add support for DMAC
> 
>  drivers/misc/pci_endpoint_test.c              |  56 ++++-
>  drivers/pci/controller/pcie-rcar-ep.c         | 227 ++++++++++++++++++
>  drivers/pci/controller/pcie-rcar.h            |  23 ++
>  drivers/pci/endpoint/functions/pci-epf-test.c | 184 ++++++++++----
>  drivers/pci/endpoint/pci-epf-core.c           |  32 +++
>  include/linux/pci-epc.h                       |   8 +
>  include/linux/pci-epf.h                       |   7 +
>  7 files changed, 483 insertions(+), 54 deletions(-)
> 
> -- 
> 2.25.1
>