mach/io.h cleanup and removal question
robherring2 at gmail.com
Fri Jun 8 10:10:17 EDT 2012
On 06/08/2012 06:43 AM, Russell King - ARM Linux wrote:
> On Fri, Jun 08, 2012 at 12:20:40PM +0200, Andrew Lunn wrote:
>> Your patchset for mach/io.h cleanup and remove, causes problems on
>> mach/io.h for orion5x had a:
>> #define IO_SPACE_LIMIT 0xffffffff
>> which got removed. This results in a panic at boot:
>> * IORESOURCE_IO
>> sys->io_offset = 0;
>> res.name = "PCIe I/O Space";
>> res.flags = IORESOURCE_IO;
>> res.start = ORION5X_PCIE_IO_BUS_BASE;
>> res.end = res.start + ORION5X_PCIE_IO_SIZE - 1;
>> if (request_resource(&ioport_resource, &res))
>> panic("Request PCIe IO resource failed\n");
>> ORION5X_PCIE_IO_SIZE is 1MB, so the allocation fails because of the
>> 64K default.
>> arch/arm/include/asm/io.h has the comment:
>> * This is the limit of PC card/PCI/ISA IO space, which is by default
>> * 64K if we have PC card, PCI or ISA support. Otherwise, default to
>> * zero to prevent ISA/PCI drivers claiming IO space (and potentially
>> * oopsing.)
>> * Only set this larger if you really need inb() et.al. to operate over
>> * a larger address space. Note that SOC_COMMON ioremaps each sockets
>> * IO space area, and so inb() et.al. must be defined to operate as per
>> * readb() et.al. on such platforms.
>> Now, i know nothing about how PCI works... So i have a question:
>> Which is better, put back parts of io.h so allowing the 1MB
>> request_resource, or reduce ORION5X_PCIE_IO_SIZE to 64KB, since from
>> the comment it is unlikely an PCI card needs more than 64KB?
> Well, the comment about SOC_COMMON doesn't apply as you're not using that.
> Probably shrinking ORION5X_PCIE_IO_SIZE to 64K, unless we really have a
> requirement to support a larger IO space.
Agreed. The next step is moving all i/o space to a fixed virtual address
and for this we want to make i/o windows 64K.
However, I think you may also have a problem with
ORION5X_PCIE_IO_BUS_BASE and the resource start. The i/o resource start
should really be 0 and then the __io() macro should add the virtual i/o
base address. However, Russell has mentioned previously that some chips
may not work correctly with i/o space at 0 (PCI bus addresses, not host).
Do you have cards with i/o that you can test or know what devices are
used with this platform?
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