There is a 64-bit division in iwl_mvm_get_crosstimestamp_fw(), which
results in a link failure when building 32-bit architectures with clang:
ld.lld: error: undefined symbol: __udivdi3
>>> referenced by ptp.c
>>> drivers/net/wireless/intel/iwlwifi/mvm/ptp.o:(iwl_mvm_phc_get_crosstimestamp) in archive vmlinux.a
GCC has optimizations for division by a constant that clang does not
implement, so this issue is not visible when building with GCC.
Use the 64-bit division helper div_u64(), which takes a u64 dividend and
u32 divisor, which matches this situation and prevents the emission of a
libcall for the division.
Fixes: 21fb8da6eb ("wifi: iwlwifi: mvm: read synced time from firmware if supported")
Reported-by: Arnd Bergmann <arnd@arndb.de>
Link: https://github.com/ClangBuiltLinux/linux/issues/1826
Reported-by: "kernelci.org bot" <bot@kernelci.org>
Link: https://lore.kernel.org/6423173a.620a0220.3d5cc.6358@mx.google.com/
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
iwl_mvm_get_sync_time() reads the gp2 from the device and then
reads the system clock. Since the two reads are not done atomically,
unexpected delays may happen between the two reads (e.g. context
switch) which make it inaccurate.
In order to improve the accuracy of the cross timestamp, call
iwl_mvm_get_sync_time() multiple times in a loop and take the
result in which the difference between the two clock is the smallest.
Signed-off-by: Avraham Stern <avraham.stern@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230320122330.d9e6f8f8998a.I569939ec4ddf0c6c64c112e7d0c30583f5509d9a@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
