Re: [PATCH 6/6] ARM: dts: Add pcie controller node for Samsung EXYNOS5440 SoC

Jingoo Han
2013-06-07T09:20:11Z

On Tuesday, April 09, 2013 1:56 AM, Jason Gunthorpe wrote:
> On Mon, Apr 08, 2013 at 06:08:53PM +0900, Jingoo Han wrote:
>
> > I have a question. Now, I am reviewing the Tegra PCIe, Marvell PCIe
> > patchset. However, in the case of Exynos PCIe, 'downstream I/O' and
> > 'non-prefetchable memory' are different between PCIe0 and PCIe1.
> > These regions are not shared.
> >
> > PCIe0:
> > ranges = <0x00000800 0 0x40000000 0x40000000 0 0x00200000 /* configuration space */
> > 0x81000000 0 0 0x40200000 0 0x00004000 /* downstream I/O */
> > 0x82000000 0 0 0x40204000 0 0x10000000>; /* non-prefetchable memory */
> >
> > PCIe1:
> > ranges = <0x00000800 0 0x40000000 0x40000000 0 0x00200000 /* configuration space */
> > 0x81000000 0 0 0x40200000 0 0x00004000 /* downstream I/O */
> > 0x82000000 0 0 0x40204000 0 0x10000000>; /* non-prefetchable memory */
> >
> > PCIe0 uses 0x40000000~0x5fffffff, PCI1 uses 0x60000000~0x7fffffff.
> >
> > How can I handle this? :)
>
> You need to dig into where this range restriction comes from, and how
> it interacts with the PCI-E root bridge's window registers. Is there
> another set of registers that control this? Is it hardwired into the
> silicon? Do the root port window registers control this?
>
> I'm looking at functions like exynos_pcie_prog_viewport_mem_outbound
> and wondering if the driver already controls this window.. But it
> looks like there may be some restrictions.
>
> Marvell also has unshared regions, but the driver arranges for those
> ranges to be setup dynamically based on writes to the bridge's window
> registers from the Linux PCI core, so the region is always in sync
> with what the Linux PCI core is trying to do.
>
> The desired perfect outcome is to have a single logical 'shared'
> region for memory and I/O - give that region to the PCI core via
> struct resources, then the PCI core tells the driver and HW what
> portion of that region belongs to each root port via a write to the
> root port bridge's window registers. The net result is still
> non-overlapping regions, but the allocation of space between port 0
> and port 1 is performed at run time.
>
> I don't really know enough about your hardware to give you better
> advice, sorry. The general guidance to try and follow the PCI-E spec
> for a root complex is good, but if the HW can't do it, or it would
> make the driver too complex, then one PCI domain per port will always
> work (this is similar to your original driver, but with domains).
>
> The main advantage to following the PCI-E specs and allowing for
> dynamic allocation of address space is that it lets you reserve less
> address space for PCI-E, and this in turn gives you more low mem
> address space to use for DRAM.

Hi Jason Gunthorpe,

I implemented 'Single domain' with Exynos PCIe for last two months;
however, it cannot work properly due to the hardware restriction.
Each MEM region is hard-wired.

Thus, I will send Exynos PCIe V3 patch as 'Separate domains'.

Best regards,
Jingoo Han

>
> > The following is right?
>
> > + pcie-controller {
> > .....
> > + ranges = <0x82000000 0 0x40000000 0x40000000 0 0x00200000 /* port 0 registers */
> > + 0x82000000 0 0x60000000 0x60000000 0 0x00200000 /* port 1 registers */
> > + 0x81000000 0 0 0x40200000 0 0x00004000 /* port 0 downstream I/O */
> > + 0x81000000 0 0 0x60200000 0 0x00004000 /* port 1 downstream I/O */
> > + 0x82000000 0 0x40204000 0x40204000 0 0x10000000>; /* port 0 non-prefetchable
> memory */
> > + 0x82000000 0 0x40204000 0x60204000 0 0x10000000>; /* port 1 non-prefetchable
> memory */
>
>
> > +
> > + pci@1,0 {
> > + device_type = "pci";
> > + assigned-addresses = <0x82000800 0 0x40000000 0 0x00200000
> > + 0x81000800 0 0x40200000 0 0x00004000
> > + 0x81000800 0 0x40204000 0 0x10000000>;
>
> Would be:
>
> ranges = <0x81000800 0 0x40200000 0x81000800 0 0x40200000 0 0x00004000
> 0x81000800 0 0x40204000 0x81000800 0 0x40204000 0 0x10000000>;
> assigned-addresses = <0x82000800 0 0x40000000 0 0x00200000>;
>
> Jason