> On Sep 29, 2016, at 5:28 PM, Jason Gunthorpe <jgunthorpe@xxxxxxxxxxxxxxxxxxxx> wrote: > > On Thu, Sep 29, 2016 at 04:26:52PM -0500, Steve Wise wrote: > >>> +/* Generally speaking, PCI systems auto-byteswap on PCI accesses, so this is >>> + probably wrong */ >>> +#define cpu_to_pci32(val) htole32(val) >> >> If this was wrong, then nothing would work. So I think you should >> remove the comment. > > I added the comment because cxgb* was the only provider that seemed to > be obviously byte swapping MMIO. > > Since htole32 is a NOP on x86 and ARM64 the driver would work fine > with or without it. Do you know this driver works on big endian > powerpc? That would help answer the question for sure. > Yes, PowerPC and arm. > I looked at this some more, and I still don't really know what is the > right answer. > > In the kernel the swapping behavior of 'writel' is architecture (and > sometimes even platform) specific. Looking at the kernel headers > suggests that BE PPC needs an explicit swap and BE ARM does not (eg > the hardware swaps). Maybe. There are a lot of layers of macros in > this area.. > > However, I can't find an obvious swap in mlx4, which I think is the > most widely tested provider. Does it work on BE PPC? > > One of the things I'd like to see done is to consolidate the mmio > accessors.. The note was a reminder to try and figure out what is > actually right here.. Appreciate any help! > Jason > -- > To unsubscribe from this list: send the line "unsubscribe linux-rdma" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
