diff options
Diffstat (limited to 'arch/arm/mach-ixp4xx/Kconfig')
| -rw-r--r-- | arch/arm/mach-ixp4xx/Kconfig | 22 |
1 files changed, 11 insertions, 11 deletions
diff --git a/arch/arm/mach-ixp4xx/Kconfig b/arch/arm/mach-ixp4xx/Kconfig index 264f4d5..9e5070d 100644 --- a/arch/arm/mach-ixp4xx/Kconfig +++ b/arch/arm/mach-ixp4xx/Kconfig @@ -179,21 +179,21 @@ config IXP4XX_INDIRECT_PCI help IXP4xx provides two methods of accessing PCI memory space: - 1) A direct mapped window from 0x48000000 to 0x4bffffff (64MB). + 1) A direct mapped window from 0x48000000 to 0x4BFFFFFF (64MB). To access PCI via this space, we simply ioremap() the BAR into the kernel and we can use the standard read[bwl]/write[bwl] macros. This is the preferred method due to speed but it - limits the system to just 64MB of PCI memory. This can be + limits the system to just 64MB of PCI memory. This can be problematic if using video cards and other memory-heavy devices. - - 2) If > 64MB of memory space is required, the IXP4xx can be - configured to use indirect registers to access PCI This allows - for up to 128MB (0x48000000 to 0x4fffffff) of memory on the bus. - The disadvantage of this is that every PCI access requires - three local register accesses plus a spinlock, but in some - cases the performance hit is acceptable. In addition, you cannot - mmap() PCI devices in this case due to the indirect nature - of the PCI window. + + 2) If > 64MB of memory space is required, the IXP4xx can be + configured to use indirect registers to access the whole PCI + memory space. This currently allows for up to 1 GB (0x10000000 + to 0x4FFFFFFF) of memory on the bus. The disadvantage of this + is that every PCI access requires three local register accesses + plus a spinlock, but in some cases the performance hit is + acceptable. In addition, you cannot mmap() PCI devices in this + case due to the indirect nature of the PCI window. By default, the direct method is used. Choose this option if you need to use the indirect method instead. If you don't know |
