RE: [EXT] Re: [PATCH 2/3] arm64: dts: ls1028a: Add PCIe controller DT nodes

[Xiaowei Bao]

Hi Arndtï

-----Original Message-----
From: Arnd Bergmann <arnd@xxxxxxxx> 
Sent: 2019å5æ17æ 16:59
To: Xiaowei Bao <xiaowei.bao@xxxxxxx>
Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>; Rob Herring <robh+dt@xxxxxxxxxx>; Mark Rutland <mark.rutland@xxxxxxx>; Shawn Guo <shawnguo@xxxxxxxxxx>; Leo Li <leoyang.li@xxxxxxx>; Kishon <kishon@xxxxxx>; Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>; gregkh <gregkh@xxxxxxxxxxxxxxxxxxx>; M.h. Lian <minghuan.lian@xxxxxxx>; Mingkai Hu <mingkai.hu@xxxxxxx>; Roy Zang <roy.zang@xxxxxxx>; Kate Stewart <kstewart@xxxxxxxxxxxxxxxxxxx>; Philippe Ombredanne <pombredanne@xxxxxxxx>; Shawn Lin <shawn.lin@xxxxxxxxxxxxxx>; linux-pci <linux-pci@xxxxxxxxxxxxxxx>; DTML <devicetree@xxxxxxxxxxxxxxx>; Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>; Linux ARM <linux-arm-kernel@xxxxxxxxxxxxxxxxxxx>; linuxppc-dev <linuxppc-dev@xxxxxxxxxxxxxxxx>
Subject: Re: [EXT] Re: [PATCH 2/3] arm64: dts: ls1028a: Add PCIe controller DT nodes

Caution: EXT Email

On Fri, May 17, 2019 at 5:21 AM Xiaowei Bao <xiaowei.bao@xxxxxxx> wrote:
> -----Original Message-----
> From: Arnd Bergmann <arnd@xxxxxxxx>
> On Wed, May 15, 2019 at 9:36 AM Xiaowei Bao <xiaowei.bao@xxxxxxx> wrote:
> > Signed-off-by: Xiaowei Bao <xiaowei.bao@xxxxxxx>
> > ---
> >  arch/arm64/boot/dts/freescale/fsl-ls1028a.dtsi |   52 ++++++++++++++++++++++++
> >  1 files changed, 52 insertions(+), 0 deletions(-)
> >
> > diff --git a/arch/arm64/boot/dts/freescale/fsl-ls1028a.dtsi 
> > b/arch/arm64/boot/dts/freescale/fsl-ls1028a.dtsi
> > index b045812..50b579b 100644
> > --- a/arch/arm64/boot/dts/freescale/fsl-ls1028a.dtsi
> > +++ b/arch/arm64/boot/dts/freescale/fsl-ls1028a.dtsi
> > @@ -398,6 +398,58 @@
> >                         status = "disabled";
> >                 };
> >
> > +               pcie@3400000 {
> > +                       compatible = "fsl,ls1028a-pcie";
> > +                       reg = <0x00 0x03400000 0x0 0x00100000   /* controller registers */
> > +                              0x80 0x00000000 0x0 0x00002000>; /* configuration space */
> > +                       reg-names = "regs", "config";
> > +                       interrupts = <GIC_SPI 108 IRQ_TYPE_LEVEL_HIGH>, /* PME interrupt */
> > +                                    <GIC_SPI 109 IRQ_TYPE_LEVEL_HIGH>; /* aer interrupt */
> > +                       interrupt-names = "pme", "aer";
> > +                       #address-cells = <3>;
> > +                       #size-cells = <2>;
> > +                       device_type = "pci";
> > +                       dma-coherent;
> > +                       num-lanes = <4>;
> > +                       bus-range = <0x0 0xff>;
> > +                       ranges = <0x81000000 0x0 0x00000000 0x80 0x00010000 0x0 0x00010000   /* downstream I/O */
> > +                                 0x82000000 0x0 0x40000000 0x80 
> > + 0x40000000 0x0 0x40000000>; /* non-prefetchable memory */
>
> Are you sure there is no support for 64-bit BARs or prefetchable memory?
> [Xiaowei Bao] sorry for late reply, Thought that our Layerscape platform has not added prefetchable memory support in DTS, so this platform has not been added, I will submit a separate patch to add prefetchable memory support for all Layerscape platforms.

Ok, thanks.

> Of course, the prefetchable PCIE device can work in our boards, 
> because the RC will assign non-prefetchable memory for this device. We 
> reserve 1G no-prefetchable memory for PCIE device, it is enough for general devices.

Sure, many devices work just fine, this is mostly a question of supporting those devices that do require multiple gigabytes, or that need prefetchable memory semantics to get the expected performance. GPUs are the obvious example, but I think there are others (infiniband?).
[Xiaowei Bao] sorry, I don't know much about infiniband and GPU, as you said, I think many devices works fine with this DTS, I will add the prefetchable memory entry in DTS future and submit another patch.

      Arnd