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

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Message-ID: <alpine.DEB.2.11.1607191034240.19980@marmot.wormnet.eu>
Date:	Tue, 19 Jul 2016 10:40:16 +0100 (BST)
From:	Jamie Lentin <jm@...tin.co.uk>
To:	Arnd Bergmann <arnd@...db.de>
cc:	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Andrew Lunn <andrew@...n.ch>,
	Florian Fainelli <f.fainelli@...il.com>,
	Jason Cooper <jason@...edaemon.net>,
	devicetree@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Gregory Clement <gregory.clement@...e-electrons.com>,
	Imre Kaloz <kaloz@...nwrt.org>,
	linux-arm-kernel@...ts.infradead.org,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
Subject: Re: [PATCH v0 06/10] arm: orion5x: Add DT-based support for Netgear
 WNR854T

On Mon, 18 Jul 2016, Arnd Bergmann wrote:

> On Monday, July 18, 2016 11:44:24 AM CEST Thomas Petazzoni wrote:
>>
>> On Sun, 17 Jul 2016 22:41:35 +0200, Arnd Bergmann wrote:
>>
>>> 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.

>>> 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.
>
>> 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.

> I was also hoping that we could get to the point where pci_common_init()
> is only used for legacy machines without DT and without multiplatform,
> it seems I missed a couple of users here.
>
> 	Arnd
>

-- 
Jamie Lentin