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Message-ID: <CAK8P3a1d6Zksdv-Or+paawyn4N0u4EpVw9QgyDGHYvX_1s3JrQ@mail.gmail.com> Date: Wed, 20 Feb 2019 11:51:34 +0100 From: Arnd Bergmann <arnd@...db.de> To: Nathan Chancellor <natechancellor@...il.com> Cc: Johannes Berg <johannes.berg@...el.com>, Emmanuel Grumbach <emmanuel.grumbach@...el.com>, Luca Coelho <luciano.coelho@...el.com>, Intel Linux Wireless <linuxwifi@...el.com>, Kalle Valo <kvalo@...eaurora.org>, linux-wireless <linux-wireless@...r.kernel.org>, Networking <netdev@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Nick Desaulniers <ndesaulniers@...gle.com> Subject: Re: [PATCH] iwlwifi: mvm: Use div64_s64 instead of do_div in iwl_mvm_debug_range_resp On Tue, Feb 19, 2019 at 7:22 PM Nathan Chancellor <natechancellor@...il.com> wrote: > > diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/ftm-initiator.c b/drivers/net/wireless/intel/iwlwifi/mvm/ftm-initiator.c > index e9822a3ec373..92b22250eb7d 100644 > --- a/drivers/net/wireless/intel/iwlwifi/mvm/ftm-initiator.c > +++ b/drivers/net/wireless/intel/iwlwifi/mvm/ftm-initiator.c > @@ -462,7 +462,7 @@ static void iwl_mvm_debug_range_resp(struct iwl_mvm *mvm, u8 index, > { > s64 rtt_avg = res->ftm.rtt_avg * 100; > > - do_div(rtt_avg, 6666); > + div64_s64(rtt_avg, 6666); This is wrong: div64_s64 does not modify its argument like do_div(), but it returns the result instead. You also don't want to divide by a 64-bit value when the second argument is a small constant. I think the correct way should be s64 rtt_avg = div_s64(res->ftm.rtt_avg * 100, 6666); If you know that the value is positive, using unsigned types and div_u64() would be slightly faster. Arnd
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