On Wednesday 23 February 2011 10:37:31 Michal Simek wrote: > Arnd Bergmann wrote: > > On Wednesday 23 February 2011 09:08:47 Michal Simek wrote: > >> Grant Likely wrote: > >>> On Tue, Feb 22, 2011 at 10:49 AM, Michal Simek <monstr@xxxxxxxxx> wrote: > >>>> i2c driver is used for LE/BE that's why is useful to use > >>>> 32bit accesses. Then it is not necessary to solve any > >>>> endian issues. > >>> Are you sure? I would expect the BE version needs to use > >>> io{read,write}32be variants of the accessors. What platforms have you > >>> tested on? > >> iowrite32 is the same with iowrite32be for Microblaze. > >> I have no problem to change it to iowrite32be if you like. > >> > >> I have tested it on microblaze big and little endian platforms. > > > > I think what Grant was saying is that iowrite32 being the same as > > iowrite32be is a bug, because iowrite32 is documented to be little-endian. > > Can you pointed me to that documentation? Documented was maybe a term that is bit too strong in this case ;-) Documentation/memory-barriers.txt documents that iowrite32 is the same as either writel or outl, depending on the source of the mapping. Both include/asm-generic/io.h and include/asm-generic/iomap.h define variants of iowrite32 and iowrite32be, but the definition in io.h is actually broken. > > This is probably fine as long as you don't have any PCI devices, > > but if you ever get PCI support, it won't work. > > Microblaze have PCI support but I don't have the board for testing. Ok, I see. > > Also, it heavily confuses other developers such as Grant and me > > if one architecture defines things to mean something completely > > different from the other architectures. > > As I see will be good to review microblaze io.h and use generic one. The generic io.h is lacking in a number of ways and should really be improved. Guan Xuetao also fell into the same trap with the unicore32 port. The problem is that I copied asm/io.h from mn10300, which seemed generic enough, but it really doesn't work correctly with PCI. There is one patch for this that I did in the unicore32 tree, I should probably go through it and fix everything else that sticks out. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html