linux-kernel - Re: [v2 3/6] of: address: add support to parse PCI outbound-ranges

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Date:   Thu, 2 Jan 2020 08:44:23 +0000
From:   "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To:     Rob Herring <robh@...nel.org>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Magnus Damm <magnus.damm@...il.com>,
        Kishon Vijay Abraham I <kishon@...com>,
        Marek Vasut <marek.vasut+renesas@...il.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        PCI <linux-pci@...r.kernel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Murray <andrew.murray@....com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        "open list:MEDIA DRIVERS FOR RENESAS - FCP" 
        <linux-renesas-soc@...r.kernel.org>,
        Chris Paterson <Chris.Paterson2@...esas.com>,
        Frank Rowand <frowand.list@...il.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Jingoo Han <jingoohan1@...il.com>,
        Simon Horman <horms@...ge.net.au>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Tom Joseph <tjoseph@...ence.com>,
        Heiko Stuebner <heiko@...ech.de>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        "Lad, Prabhakar" <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [v2 3/6] of: address: add support to parse PCI outbound-ranges

Hi Rob,

On Thu, Dec 19, 2019 at 11:31 PM Rob Herring <robh@...nel.org> wrote:
>
> On Mon, Dec 16, 2019 at 08:49:23AM +0000, Lad, Prabhakar wrote:
> > Hi Rob,
> >
> > Thank you for the review.
> >
> > On Fri, Dec 13, 2019 at 8:37 PM Rob Herring <robh+dt@...nel.org> wrote:
> > >
> > > On Fri, Dec 13, 2019 at 2:48 AM Lad Prabhakar
> > > <prabhakar.csengg@...il.com> wrote:
> > > >
> > > > From: "Lad, Prabhakar" <prabhakar.mahadev-lad.rj@...renesas.com>
> > > >
> > > > this patch adds support to parse PCI outbound-ranges, the
> > > > outbound-regions are similar to pci ranges except it doesn't
> > > > have pci address, below is the format for bar-ranges:
> > > >
> > > > outbound-ranges = <flags upper32_cpuaddr lower32_cpuaddr
> > > >                    upper32_size lower32_size>;
> > >
> > > You can't just make up a new ranges property. Especially one that
> > > doesn't follow how 'ranges' works. We already have 'dma-ranges' to
> > > translate device to memory addresses.
> > >
> > > Explain the problem or feature you need, not the solution you came up
> > > with. Why do you need this and other endpoint bindings haven't?
> > >
> > rcar SoC's supports multiple outbound region for mapping the PCI address
> > locally to the system. This lead to discussion where there exist controllers
> > which support regions for high/low priority transfer and similarly regions
> > for large/small memory allocations, as a result a new ranges property was
> > added, where we can specify the flags which would indicate how the outbound
> > region can be used during requests.
>
> What are the flags?

below are the flags which were discussed in first version of the
series, but since the driver is
currently using just PCI_EPC_WINDOW_FLAG_NON_MULTI_ALLOC flag I'll be
dropping them in
next version (suggested by Kishon) and rest will be added as and when
required by the driver.

 * @PCI_EPC_WINDOW_FLAG_MULTI_ALLOC: Indicates multiple chunks of memory can be
 *                                  allocated from same window
 * @PCI_EPC_WINDOW_FLAG_NON_MULTI_ALLOC: Indicates only single memory allocation
 *                                      is possible on the window
 * @PCI_EPC_WINDOW_FLAG_LARGE_ALLOC: Window is used for large memory allocation
 * @PCI_EPC_WINDOW_FLAG_SMALL_ALLOC: Window is used for small memory allocation
 * @PCI_EPC_WINDOW_FLAG_HIGH_PRI_ALLOC: Window is used for high priority data
 *                                     transfers
 * @PCI_EPC_WINDOW_FLAG_LOW_PRI_ALLOC: Window is used for low priority data
 *                                    transfers

Cheers,
--Prabhakar