On Fri, Dec 4, 2015 at 2:50 AM, Catalin Marinas <[email protected]> wrote: > On Fri, Nov 20, 2015 at 02:20:26PM +0000, Brian Starkey wrote: >> When the DMA_MEMORY_MAP flag is used, memory which can be accessed >> directly should be returned, so use ioremap_wc() instead of ioremap(). >> Also, ensure that the correct memset operation is used in >> dma_alloc_from_coherent() with respect to the region's flags. >> >> This fixes the below alignment fault on arm64, caused by invalid use >> of memset() on Device memory. > > This is indeed affecting both arm32 and arm64 systems. > >> diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c >> index 55b8398..45358d0 100644 >> --- a/drivers/base/dma-coherent.c >> +++ b/drivers/base/dma-coherent.c >> @@ -31,7 +31,10 @@ static int dma_init_coherent_memory(phys_addr_t >> phys_addr, dma_addr_t device_add >> if (!size) >> goto out; >> >> - mem_base = ioremap(phys_addr, size); >> + if (flags & DMA_MEMORY_MAP) >> + mem_base = ioremap_wc(phys_addr, size); >> + else >> + mem_base = ioremap(phys_addr, size); > > I wonder whether a memremap() approach for the DMA_MEMORY_MAP case would > be better. This API was added recently by commit 92281dee825f ("arch: > introduce memremap()"). It only supports write-back and write-through > but we could add a MEMREMAP_WC flag for this case.
I originally included both MEMREMAP_WC and MEMREAMP_UC as potential flags to this api, but ultimately decided against it. The memremap() api is meant for memory that is known to have no i/o side effects. As far as I can see WC and UC usages are a muddy mix of "sometimes there's I/O side effects, but it depends by arch and driver". In other words we can't drop the "__iomem" annotation from WC and UC mappings by default. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
