On Thursday 28 September 2006 10:33, JWM wrote: > My problem is that I'm trying make sure that buffers on a PCI device get > written to with write combining enabled. Please keep linux-ia64 copied, so other people can benefit from this discussion. > I used memmap at the EFI prompt and it shows the regions where the > device memory is as available (which are). > > 0xCBE00000 - 0xCBEFFFFF This MMIO region isn't described at all in the EFI memory map, so the kernel has no idea what attributes are supported. That's why efi_range_is_wc() returns 0 for this range. Your firmware people will likely respond that this MMIO region is described via ACPI. But Linux isn't smart enough yet to use ACPI for this purpose. I assume you're trying to map this region in the kernel, so a driver can access it. Normally you would use ioremap() or ioremap_nocache() or maybe even pci_iomap() for this purpose. But there's currently no good way to ask for a write-combining mapping. Some people have suggested an ioremap_wc(), but I guess the idea hasn't achieved critical mass yet. > The ia64 ioremap doesn't seem to do the vma mappings that other > platforms do. Right. On ia64, ioremap() uses kernel identity mappings for which there are no page tables. If we did implement ioremap_wc(), we would have to do it with page tables so there would be a place to set the WC attribute. > After googleing the problem I've found one set of messages > indicating that the last person that did this had to roll their own > remap_area_pages and supporting routines. > Is that the way to go or is it just that I don't understand something > about the platform? I think the high-speed interconnect folks are interested in this, and as far as I know, they have had to roll their own stuff so far (I haven't actually seen it). I would think lots of people would be interested in this, so if you came up with an ioremap_wc() implementation that is generically useful, you might be able to make it fly. > BS_data 0000000000000000-0000000000000FFF 0000000000000001 0000000000000008 > available 0000000000001000-000000000008AFFF 000000000000008A 0000000000000008 > BS_data 000000000008B000-000000000009FFFF 0000000000000015 0000000000000008 > RT_code 00000000000C0000-00000000000DFFFF 0000000000000020 8000000000000001 > RT_code 00000000000E0000-00000000000FFFFF 0000000000000020 8000000000000008 > available 0000000000100000-0000000077FFFFFF 0000000000077F00 0000000000000008 > RT_data 0000000078000000-000000007BFFFFFF 0000000000004000 8000000000000001 > available 000000007C000000-000000007E9ABFFF 00000000000029AC 0000000000000008 > RT_data 000000007E9AC000-000000007E9B1FFF 0000000000000006 8000000000000008 > RT_code 000000007E9B2000-000000007EDC5FFF 0000000000000414 8000000000000008 > RT_data 000000007EDC6000-000000007EF2DFFF 0000000000000168 8000000000000008 > RT_data 000000007EF2E000-000000007EF37FFF 000000000000000A 8000000000000008 > RT_data 000000007EF38000-000000007EFFFFFF 00000000000000C8 8000000000000008 > PAL_code 000000007F000000-000000007F2FFFFF 0000000000000300 8000000000000008 > available 000000007F300000-000000007FDF8FFF 0000000000000AF9 0000000000000008 > BS_data 000000007FDF9000-000000007FE07FFF 000000000000000F 0000000000000008 > RT_code 000000007FE08000-000000007FE0FFFF 0000000000000008 8000000000000008 > BS_data 000000007FE10000-000000007FE15FFF 0000000000000006 0000000000000008 > RT_code 000000007FE16000-000000007FFFFFFF 00000000000001EA 8000000000000008 > RT_data 00000000FF000000-00000000FFFFFFFF 0000000000001000 8000000000000001 > available 0000000100000000-000000047744DFFF 000000000037744E 0000000000000008 > BS_data 000000047744E000-000000047B7FDFFF 00000000000043B0 0000000000000008 > RT_data 000000047B7FE000-000000047F7FFFFF 0000000000004002 8000000000000008 > BS_data 000000047F800000-000000047F800FFF 0000000000000001 0000000000000008 > available 000000047F801000-000000047F8C5FFF 00000000000000C5 0000000000000008 > BS_data 000000047F8C6000-000000047F8C7FFF 0000000000000002 0000000000000008 > available 000000047F8C8000-000000047F8C9FFF 0000000000000002 0000000000000008 > BS_data 000000047F8CA000-000000047F9F9FFF 0000000000000130 0000000000000008 > available 000000047F9FA000-000000047F9FAFFF 0000000000000001 0000000000000008 > BS_data 000000047F9FB000-000000047F9FDFFF 0000000000000003 0000000000000008 > available 000000047F9FE000-000000047FD27FFF 000000000000032A 0000000000000008 > RT_code 000000047FD28000-000000047FD91FFF 000000000000006A 8000000000000008 > BS_code 000000047FD92000-000000047FDFDFFF 000000000000006C 0000000000000008 > available 000000047FDFE000-000000047FE2DFFF 0000000000000030 0000000000000008 > RT_code 000000047FE2E000-000000047FE7DFFF 0000000000000050 8000000000000008 > available 000000047FE7E000-000000047FFB5FFF 0000000000000138 0000000000000008 > RT_data 000000047FFB6000-000000047FFFFFFF 000000000000004A 8000000000000008 > MemPortIO 00000FFFFC000000-00000FFFFFFFFFFF 0000000000004000 8000000000000001 - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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