On Wed, 22 Nov 2017, Jesper Nilsson wrote: > On Mon, Nov 20, 2017 at 10:50:46PM -0500, Nicolas Pitre wrote: > > On Mon, 20 Nov 2017, Guenter Roeck wrote: > > > On Mon, Nov 20, 2017 at 07:28:21PM -0500, Nicolas Pitre wrote: > > > > On Mon, 20 Nov 2017, Guenter Roeck wrote: > > > > > > > > > bdata->node_min_pfn=60000 PFN_PHYS(bdata->node_min_pfn)=c0000000 start_off=536000 region=c0536000 > > > > > > > > If PFN_PHYS(bdata->node_min_pfn)=c0000000 and > > > > region=c0536000 that means phys_to_virt() is a no-op. > > > > > > > No, it is |= 0x80000000 > > > > Then the bootmem registration looks very fishy. If you have: > > > > > I think the problem is the 0x60000 in bdata->node_min_pfn. It is shifted > > > left by PFN_PHYS, making it 0xc0000000, which in my understanding is > > > a virtual address. > > > > Exact. > > > > #define __pa(x) ((unsigned long)(x) & 0x7fffffff) > > #define __va(x) ((void *)((unsigned long)(x) | 0x80000000)) > > > > With that, the only possible physical address range you may have is > > 0x40000000 - 0x7fffffff, and it better start at 0x40000000. If that's > > not where your RAM is then something is wrong. > > > > This is in fact a very bad idea to define __va() and __pa() using > > bitwise operations as this hides mistakes like defining physical RAM > > address at 0xc0000000. Instead, it should look like: > > > > #define __pa(x) ((unsigned long)(x) - 0x80000000) > > #define __va(x) ((void *)((unsigned long)(x) + 0x80000000)) > > > > This way, bad physical RAM address definitions will be caught > > immediately. > > > > > That doesn't seem to be easy to fix. It seems there is a mixup of physical > > > and virtual addresses in the architecture. > > > > Well... I don't think there is much else to say other than this needs > > fixing. > > The memory map for the ETRAX FS has the SDRAM mapped at both 0x40000000-0x7fffffff > and 0xc0000000-0xffffffff, and the difference is cached and non-cached. > That is actively (ab)used in the port, unfortunately, allthough I'm > uncertain if this is the problem in this case. It certainly is a problem. If your cached RAM is physically mapped at 0xc0000000 and you want it to be virtually mapped at 0xc0000000 then you should have: #define __pa(x) ((unsigned long)(x)) #define __va(x) ((void *)(x)) i.e. no translation. For non-cached RAM access, there are specific interfaces for that. For example, you could have dma_alloc_coherent() take advantage of the fact that memory with the top bit cleared becomes uncached. But __pa() is the wrong interface for obtaining uncached memory. Nicolas -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
