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In-Reply-To: From: Ard Biesheuvel Date: Fri, 17 May 2019 12:44:22 +0200 Message-ID: Subject: Re: [EXT] Re: [PATCH 2/3] arm64: dts: ls1028a: Add PCIe controller DT nodes To: Arnd Bergmann Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Roy Zang , Lorenzo Pieralisi , Xiaowei Bao , DTML , gregkh , Shawn Lin , Philippe Ombredanne , Mingkai Hu , Linux Kernel Mailing List , Kishon , "M.h. Lian" , Rob Herring , Linux ARM , linux-pci , Bjorn Helgaas , Shawn Guo , Leo Li , linuxppc-dev , Kate Stewart Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Fri, 17 May 2019 at 10:59, Arnd Bergmann wrote: > > On Fri, May 17, 2019 at 5:21 AM Xiaowei Bao wrote: > > -----Original Message----- > > From: Arnd Bergmann > > On Wed, May 15, 2019 at 9:36 AM Xiaowei Bao wrote= : > > > Signed-off-by: Xiaowei Bao > > > --- > > > 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/ar= m64/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 =3D "disabled"; > > > }; > > > > > > + pcie@3400000 { > > > + compatible =3D "fsl,ls1028a-pcie"; > > > + reg =3D <0x00 0x03400000 0x0 0x00100000 /* = controller registers */ > > > + 0x80 0x00000000 0x0 0x00002000>; /* co= nfiguration space */ > > > + reg-names =3D "regs", "config"; > > > + interrupts =3D , /* PME interrupt */ > > > + ; /* aer interrupt */ > > > + interrupt-names =3D "pme", "aer"; > > > + #address-cells =3D <3>; > > > + #size-cells =3D <2>; > > > + device_type =3D "pci"; > > > + dma-coherent; > > > + num-lanes =3D <4>; > > > + bus-range =3D <0x0 0xff>; > > > + ranges =3D <0x81000000 0x0 0x00000000 0x80 0x= 00010000 0x0 0x00010000 /* downstream I/O */ > > > + 0x82000000 0x0 0x40000000 0x80 0x40= 000000 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 platfor= m has not added prefetchable memory support in DTS, so this platform has no= t been added, I will submit a separate patch to add prefetchable memory sup= port 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-prefet= chable > > memory for PCIE device, it is enough for general devices. > > Sure, many devices work just fine, this is mostly a question of supportin= g those > devices that do require multiple gigabytes, or that need prefetchable mem= ory > semantics to get the expected performance. GPUs are the obvious example, > but I think there are others (infiniband?). > Some implementations of the Synopsys dw PCIe IP contain a 'root port' (within quotes because it is not actually a root port but an arbitrary set of MMIO registers that looks like a type 01 config region) that does not permit the prefetchable bridge window BAR to be written (a thing which is apparently permitted by the PCIe spec). So while the host bridge is capable of supporting more than one MMIO BAR window, the OS visible software interface does not expose this functionality In practice, it probably doesn't matter, since the driver uses the same iATU attributes for prefetchable and non-prefetchable windows, but I guess 1 GB of MMIO BAR space is a bit restrictive for modern systems.