[PATCH v0 06/10] arm: orion5x: Add DT-based support for Netgear WNR854T

On Tuesday, July 19, 2016 10:40:16 AM CEST Jamie Lentin wrote:

On Mon, 18 Jul 2016, Arnd Bergmann wrote:

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On Monday, July 18, 2016 11:44:24 AM CEST Thomas Petazzoni wrote:

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On Sun, 17 Jul 2016 22:41:35 +0200, Arnd Bergmann wrote:

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I would assume that the PCIe port should work out of the box with the driver

Unfortunately, no. The PCIe on Orion5x requires a workaround for
reading/writing the PCI configuration space. Instead of doing MMIO
accesses to PCIE_CONF_ADDR_OFF / PCIE_CONF_DATA_OFF, you must map a
MBus window, which provides a memory-mapped view of the PCI
configuration space.

Definitely not impossible to implement, but the driver doesn't work
as-is.

Ok.

Unfortunately this isn't something I can test as the PCIe port on the SoC 
doesn't go anywhere in my case.

As I said, this wouldn't be a problem: we should consider the PCI and PCIe
ports on this chip as completely separate anyway, so we can work on
the drivers independently.

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We also don't seem to need any MBUS window setup for the I/O and
memory spaces, which greatly simplifies the driver compared to the
pci-mvebu one, it would be a fairly straightforward implementation
based on pci-host-generic.c (which unfortunately just got way
more complicated and might need to go on a diet).

MBus windows are needed. See:

        mvebu_mbus_add_window_remap_by_id(ORION_MBUS_PCI_IO_TARGET,
                                          ORION_MBUS_PCI_IO_ATTR,
                                          ORION5X_PCI_IO_PHYS_BASE,
                                          ORION5X_PCI_IO_SIZE,
                                          ORION5X_PCI_IO_BUS_BASE);
        mvebu_mbus_add_window_by_id(ORION_MBUS_PCI_MEM_TARGET,
                                    ORION_MBUS_PCI_MEM_ATTR,
                                    ORION5X_PCI_MEM_PHYS_BASE,
                                    ORION5X_PCI_MEM_SIZE);

in orion5x_setup_wins().

Ok, I was just looking at the wrong file, as they are set up from
common.c, not pci.c.

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Note that we already have some Orion5x converted to DT, and that use
PCI: board-rd88f5182.c is an example. So we could very well take Jamie
patches as-is, and move later to a DT-representation for PCI/PCIe.

Ah, I thought all the DT users were moved to mach-mvebu. I agree
this new patch isn't introducing anything we don't already have then,
so we can just take it, but the conversion will not be nice when
we do that.

Yes, board-wnr854t.c is a clone of the existing board-rd88f5182.c. 
Although I'd presume that it too would need late_initcall() or somesuch 
mechanism to probe PCI once the GPIO controller is available.

Deferred probing should be fine once the driver is migrated from
pci_common_init() to registering the host bridge directly.

	Arnd