linux-kernel - Re: [RFC PATCH 5/6] arm64: dts: ti: Add Support for AM654 SoC

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Message-ID: <20180827155535.GJ7523@atomide.com>
Date:   Mon, 27 Aug 2018 08:55:35 -0700
From:   Tony Lindgren <tony@...mide.com>
To:     Kishon Vijay Abraham I <kishon@...com>
Cc:     Rob Herring <robh+dt@...nel.org>, Nishanth Menon <nm@...com>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mark Rutland <mark.rutland@....com>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        devicetree@...r.kernel.org,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        Vignesh R <vigneshr@...com>, Tero Kristo <t-kristo@...com>,
        Russell King <linux@...linux.org.uk>,
        Sudeep Holla <sudeep.holla@....com>
Subject: Re: [RFC PATCH 5/6] arm64: dts: ti: Add Support for AM654 SoC

* Kishon Vijay Abraham I <kishon@...com> [180827 03:06]:
> Hi Tony,
> 
> On Monday 20 August 2018 08:01 PM, Tony Lindgren wrote:
> > * Kishon Vijay Abraham I <kishon@...com> [180808 06:35]:
> >> On Tuesday 05 June 2018 07:35 PM, Rob Herring wrote:
> >>> Really need 64-bit addresses and sizes? Use ranges to limit the
> >>> address space if possible.
> >>
> >> We now have address-cells as <1>,
> >> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/arch/arm64/boot/dts/ti/k3-am65.dtsi#n49
> >>
> >> However each PCIe instance has 2 data regions and one of the regions
> >> (PCIE0_CORE_CORE_DAT_SLV_PCIE_DAT1/PCIE1_CORE_CORE_DAT_SLV_PCIE_DAT1 specified
> >> in the "MAIN Domain Memory Map" table of TRM http://www.ti.com/lit/pdf/spruid7)
> >> is above the 32bit region and requires 2 cells to specify the start address.
> >> This region is used to access MEM_SPACE of PCIe endpoint when operating in root
> >> complex mode and access memory of PCI root complex when operating in endpoint mode.
> >>
> >> In order to describe this, should we change the address-cells back to <2> or do
> >> you suggest any other alternatives?
> > 
> > It's probably best to have the top level cbass interconnect use
> > #size-cells = <2> and then have it's child interconnects have
> > #size-cells = <1> if they don't need ranges above 4GB.
> 
> PCIe has a region starting at 0x40_00000000 and size 4GB. We need 2 address
> cells and 2 size cells to describe this no?

Yes.

> > BTW, what's the difference between all these three similar PCIE
> > ranges?
> > 
> > PCIE0_CORE_CORE_DAT_SLV_PCIE_CORE 0x0005500000 0x0005600000 1 MB
> > PCIE1_CORE_CORE_DAT_SLV_PCIE_CORE 0x0005600000 0x0005700000 1 MB
> 
> This is the register space for the two instances of PCIe controller.
> > 
> > PCIE0_CORE_CORE_DAT_SLV_PCIE_DAT0 0x0010000000 0x0018000000 128 MB
> > PCIE1_CORE_CORE_DAT_SLV_PCIE_DAT0 0x0018000000 0x0020000000 128 MB
> > 
> > PCIE0_CORE_CORE_DAT_SLV_PCIE_DAT1 0x4000000000 0x4100000000 4 GB
> > PCIE1_CORE_CORE_DAT_SLV_PCIE_DAT1 0x4100000000 0x4200000000 4 GB
> 
> The above are regions which can be used by CPU/DMA to access the PCIe address
> space. The mapping from the above regions to the PCIe address space will be
> programmed in the PCIe controller.

OK so not just somethng for dma-ranges but also accessible by
the CPU.

Regards,

Tony