On Wed, Jun 15, 2016 at 6:27 PM, Arnd Bergmann <[email protected]> wrote: > The mlx5 driver fails to build on 32-bit architectures after some > references to 64-bit divisions got added: > > drivers/net/built-in.o: In function `mlx5e_rx_am': > :(.text+0xf88ac): undefined reference to `__aeabi_ldivmod' > > The driver even performs three division here, and it uses the > obsolete 'struct timespec' that we want to get rid of. > > Using ktime_t and ktime_us_delta() replaces one of the divisions > and is mildly more efficient, aside from working across 'settimeofday' > calls and being the right type for the y2038 conversion. > > Using a u32 instead of s64 to store the number of microseconds > limits the maximum time to about 71 minutes, but if we exceed that > time, we probably don't care about the result any more for the > purpose of rx coalescing. > > For the number of packets, we are taking the difference between > two 'unsigned int', so the result won't ever be greater than that > either. > > After those changes, the other two divisions are done as 32-bit > arithmetic operations, which are much faster.
Nice catch Arnd, we originally fixed this with div_u64, but your solution looks wiser. does ktime_t gives time in a resolution same as timespec ? As discussed before this patch can't be applied on net-next as the original patch which it meant to fix is yet to be submitted, I will CC you once we submit the fixed patch.
