On Wed, 2008-12-10 at 11:33 -0800, Trent Piepho wrote: > On Wed, 10 Dec 2008, Benjamin Herrenschmidt wrote: > > This changes the logic so that instead, the PTE now contains > > _PAGE_COHERENT for all normal RAM pages tha have I = 0. The hash > > code clears it if the feature bit is not set. > > Why not check the feature bit when the PTE is made and unset _PAGE_COHERENT > at that point? In fact, could you do something like:
Not sure what you mean. Inside set_pte_at ? Well, the one line of asm is going to be in the noise in the hash code, I'm just flipping an existing condition. I like the PTE to represent whether it's supposed to be a coherent page. > #if defined(CONFIG_SMP) || .... > #define _PAGE_BASE (_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_COHERENT) > #else > #define _PAGE_BASE (_PAGE_PRESENT | _PAGE_ACCESSED) > #endif Not sure what your condition above is supposed to be but the whole thing with the MPC107 bridge etc... should _NOT_ be a config option, that's bogus, it should all be runtime detected. Right now we have a problem because the CPU feature fixups are done wayyyy too early on ppc32 so it's pretty much impossible to whack the feature bit from the platform code but I intend to fix that at some I've been told that setting M on non-SMP will slows things down. But > couldn't you just change _PAGE_BASE on non-SMP instead of clearning it in > the miss handler? Well, because we need it set on non SMP on some 74xx.. maybe we can have it set in PAGE_BASE only if CONFIG_SMP and CONFIG_6xx ? I'm also not sure about some other upcoming SMP BookE processors that may require M for DMA cache coherency. > I have a patch to remove this IORESOURCE_PREFETCH hack. The current kernel > creates two files, resourceN and resourceN_wc, for prefetchable BARs to > allow the user to choose what mode to use. Ah ? That's new ? I missed it. Has X been updated to use them ? If not, keep the hack for a little while more :-) > Though I want to be able to map PCI resources as cached too. I'm not sure > what a good way to add that is. Yet another resource file? The first > proposal for allowing WC mappings was to add support for ioctl() on sysfs > attributes. Then one could use ioctl() after opening the resource file to > specify what mode to map it with. No one liked ioctl(), but clearly the > current method doesn't scale well to all 32 combinations of the WIMGE bits. True. Dunno what the right approach is at this stage, best to discuss this on linux-pci. Cheers. Ben. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
