On Friday 13 November 2015 03:10:13 Andy Shevchenko wrote: > On Thu, Nov 12, 2015 at 4:14 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote: > > The dw_mmc driver stores the physical address of the MMIO registers > > in a pointer, which requires the use of type casts, and is actually > > broken if anyone ever has this device on a 32-bit SoC in registers > > above 4GB. Gcc warns about this possibility when the driver is built > > with ARM LPAE enabled: > > > - host->phy_regs = (void *)(regs->start); > > + host->phy_regs = regs->start; > > > /* Set external dma config: burst size, burst width */ > > - cfg.dst_addr = (dma_addr_t)(host->phy_regs + fifo_offset); > > + cfg.dst_addr = host->phy_regs + fifo_offset; > > dst_addr is dma_addr_t? Sort of. It doesn't really fit into any of the categories, and we actually had a patch to change the type in the past, see https://lkml.org/lkml/2015/7/10/167. Not sure what is going on there. > > /* Registers's physical base address */ > > - void *phy_regs; > > + resource_size_t phy_regs; > > If dst_addr is dma_addr_t wouldn't be a problem when > resource_size_t is defined as 64-bit address, and dma_addr_t as 32-bit? > > Btw, for me casting to dma_addr_t looks sane. The background here is that the address comes from a resource_size_t that describes the MMIO register area as seen from the CPU, and that is normally a phys_addr_t (resource_size_t is defined as being long enough to store a phys_addr_t or various other things depending on resource->flags). dma_addr_t strictly speaking refers to a RAM location as seen by a DMA master, and that only comes out of dma_map_*() or dma_alloc_coherent(). The DMA engine wants something else here, which is an MMIO register address as seen by a DMA master, and we don't have a separate typedef for that. Almost universally all of resource_size_t, phys_addr_t and dma_addr_t are the same type, and if we ever get a platform that wants something other than a phys_addr_t to put into cfg.dst_addr, we are in deep trouble. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
