On Thursday 14 May 2015 18:49:17 Timur Tabi wrote:
Guenter Roeck wrote:
We still don't know if the registers are in host byte order or in little endian order. If registers are in host byte order, there is no need for a conversion.
Well, if I compile and boot a big-endian ARM64 kernel, then I don't expect the hardware devices to magically switch all their registers into big endian. The devices will remain little-endian.
I presume that this is true on all ARM and ARM64 systems. Switching the CPU into big-endian mode (when it normally would run in little-endian) does not also switch the hardware registers.
Therefore, if we want to support big-endian kernels on ARM64, then every readl/writel in every driver must use cpu_to_le32/etc.
I think this conversation has gone off-track. I don't see how the SBSA watchdog device is any different from any other device on an ARM64 platform.
I think it's safe to say that the endian order is not specified anywhere, but on my hardware, everything is little-endian.
Then please remove the double-swap. If the device works like any other device in the system, then the byteswap that is implied by readl/writel will do the right thing, and swapping twice will break big-endian kernels.
Arnd