linux-kernel - Re: [EXT] 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:   Fri, 25 Mar 2022 17:13:02 +0000
From:   "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To:     Kishon Vijay Abraham I <kishon@...com>
Cc:     Frank Li <frank.li@....com>, Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.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 <linux-pci@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Biju Das <biju.das.jz@...renesas.com>
Subject: Re: [EXT] Re: [RFC PATCH 0/5] PCIe EPF support for internal DMAC
 handling and driver update for R-Car PCIe EP to support DMAC

Hi Kishon,

On Wed, Mar 2, 2022 at 6:28 PM Frank Li <frank.li@....com> wrote:
>
>
>
> > -----Original Message-----
> > From: Lad, Prabhakar <prabhakar.csengg@...il.com>
> > Sent: Wednesday, March 2, 2022 11:18 AM
> > To: Frank Li <frank.li@....com>
> > Cc: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>; Lad Prabhakar
> > <prabhakar.mahadev-lad.rj@...renesas.com>; 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 <linux-pci@...r.kernel.org>; Linux-Renesas <linux-renesas-
> > soc@...r.kernel.org>; LKML <linux-kernel@...r.kernel.org>; Biju Das
> > <biju.das.jz@...renesas.com>
> > Subject: [EXT] Re: [RFC PATCH 0/5] PCIe EPF support for internal DMAC
> > handling and driver update for R-Car PCIe EP to support DMAC
> >
> > Caution: EXT Email
> >
> > Hi Frank,
> >
> > On Wed, Mar 2, 2022 at 3:42 PM Frank Li <frank.li@....com> wrote:
> > >
> > >
> > >
> > > > -----Original Message-----
> > > > From: Lad, Prabhakar <prabhakar.csengg@...il.com>
> > > > Sent: Thursday, February 10, 2022 3:24 AM
> > > > To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > > > Cc: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>; 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 <linux-pci@...r.kernel.org>; Linux-Renesas
> > > > <linux-renesas-soc@...r.kernel.org>; LKML <linux-
> > kernel@...r.kernel.org>;
> > > > Biju Das <biju.das.jz@...renesas.com>
> > > > Subject: [EXT] Re: [RFC PATCH 0/5] PCIe EPF support for internal DMAC
> > > > handling and driver update for R-Car PCIe EP to support DMAC
> > >
> > > I use standard DMA engine API to implement Designware PCIE EP embedded
> > DMA support.
> > > Please check
> > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kern
> > el.org%2Fall%2F20220302032646.3793-3-
> > Frank.Li%40nxp.com%2FT%2F&amp;data=04%7C01%7Cfrank.li%40nxp.com%7C0e2e5fe8f
> > d224076afb208d9fc70aa16%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637818
> > 383096028914%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLC
> > JBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=DCDX%2BYEVFsPOE6ZWzwrMxk1Fjlk
> > ZA%2FEPGmhQSHuPB2c%3D&amp;reserved=0
> > >
> > Thank you for the link. The Designware PCIE EP is implemented as a DMA
> > engine driver so it's convenient to use the DMA engine API, whereas
> > the R-Car PCIe-EP is implemented as an actual PCIe EP [0].
>
> My means, needn't add new interface pci_epf_internal_dmac_xfr at epc/epf.
> Your R-Car PCI-EP DMA part can implement as a dma engine driver like designware.
>
> So EP functional driver use the same method to operate DMA regardless
> EP controller type.
>
With this approach all the PCIe controllers supporting internal dmac
will have to be added as a DMA driver.

Could you please provide some feedback on the above?

Sorry this mail is not in chain to my orignal patch series. My orignal
series can be found at [0]

[0] https://patchwork.kernel.org/project/linux-renesas-soc/cover/20220126195043.28376-1-prabhakar.mahadev-lad.rj@bp.renesas.com/

Cheers,
Prabhakar