From patchwork Wed Mar 9 23:13:04 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kamal Mostafa X-Patchwork-Id: 595416 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from huckleberry.canonical.com (huckleberry.canonical.com [91.189.94.19]) by ozlabs.org (Postfix) with ESMTP id 818A0140322; Thu, 10 Mar 2016 10:15:35 +1100 (AEDT) Received: from localhost ([127.0.0.1] helo=huckleberry.canonical.com) by huckleberry.canonical.com with esmtp (Exim 4.76) (envelope-from ) id 1adnKG-0003Mb-AJ; Wed, 09 Mar 2016 23:15:32 +0000 Received: from youngberry.canonical.com ([91.189.89.112]) by huckleberry.canonical.com with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.76) (envelope-from ) id 1adnHw-00023i-Kp for kernel-team@lists.ubuntu.com; Wed, 09 Mar 2016 23:13:08 +0000 Received: from 1.general.kamal.us.vpn ([10.172.68.52] helo=fourier) by youngberry.canonical.com with esmtpsa (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.76) (envelope-from ) id 1adnHw-0002Wl-6Q; Wed, 09 Mar 2016 23:13:08 +0000 Received: from kamal by fourier with local (Exim 4.86) (envelope-from ) id 1adnHt-0003mM-GH; Wed, 09 Mar 2016 15:13:05 -0800 From: Kamal Mostafa To: Eugenia Emantayev Subject: [3.13.y-ckt stable] Patch "net/mlx4_en: Choose time-stamping shift value according to HW frequency" has been added to the 3.13.y-ckt tree Date: Wed, 9 Mar 2016 15:13:04 -0800 Message-Id: <1457565184-14491-1-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 2.7.0 X-Extended-Stable: 3.13 Cc: Kamal Mostafa , Matan Barak , kernel-team@lists.ubuntu.com, Or Gerlitz , "David S . Miller" X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.14 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: kernel-team-bounces@lists.ubuntu.com This is a note to let you know that I have just added a patch titled net/mlx4_en: Choose time-stamping shift value according to HW frequency to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree which can be found at: http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.13.y-queue This patch is scheduled to be released in version 3.13.11-ckt36. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.13.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ---8<------------------------------------------------------------ From 95b94a5395d69216fe31e1d0f1ec8b5db1bbdc7a Mon Sep 17 00:00:00 2001 From: Eugenia Emantayev Date: Wed, 17 Feb 2016 17:24:23 +0200 Subject: net/mlx4_en: Choose time-stamping shift value according to HW frequency commit 31c128b66e5b28f468076e4f3ca3025c35342041 upstream. Previously, the shift value used for time-stamping was constant and didn't depend on the HW chip frequency. Change that to take the frequency into account and calculate the maximal value in cycles per wraparound of ten seconds. This time slot was chosen since it gives a good accuracy in time synchronization. Algorithm for shift value calculation: * Round up the maximal value in cycles to nearest power of two * Calculate maximal multiplier by division of all 64 bits set to above result * Then, invert the function clocksource_khz2mult() to get the shift from maximal mult value Fixes: ec693d47010e ('net/mlx4_en: Add HW timestamping (TS) support') Signed-off-by: Eugenia Emantayev Reviewed-by: Matan Barak Signed-off-by: Or Gerlitz Signed-off-by: David S. Miller Signed-off-by: Luis Henriques Signed-off-by: Kamal Mostafa --- drivers/net/ethernet/mellanox/mlx4/en_clock.c | 25 +++++++++++++++++++------ 1 file changed, 19 insertions(+), 6 deletions(-) -- 2.7.0 diff --git a/drivers/net/ethernet/mellanox/mlx4/en_clock.c b/drivers/net/ethernet/mellanox/mlx4/en_clock.c index fd64410..9180c7e 100644 --- a/drivers/net/ethernet/mellanox/mlx4/en_clock.c +++ b/drivers/net/ethernet/mellanox/mlx4/en_clock.c @@ -111,6 +111,24 @@ void mlx4_en_fill_hwtstamps(struct mlx4_en_dev *mdev, hwts->hwtstamp = ns_to_ktime(nsec); } +#define MLX4_EN_WRAP_AROUND_SEC 10ULL + +/* This function calculates the max shift that enables the user range + * of MLX4_EN_WRAP_AROUND_SEC values in the cycles register. + */ +static u32 freq_to_shift(u16 freq) +{ + u32 freq_khz = freq * 1000; + u64 max_val_cycles = freq_khz * 1000 * MLX4_EN_WRAP_AROUND_SEC; + u64 max_val_cycles_rounded = is_power_of_2(max_val_cycles + 1) ? + max_val_cycles : roundup_pow_of_two(max_val_cycles) - 1; + /* calculate max possible multiplier in order to fit in 64bit */ + u64 max_mul = div_u64(0xffffffffffffffffULL, max_val_cycles_rounded); + + /* This comes from the reverse of clocksource_khz2mult */ + return ilog2(div_u64(max_mul * freq_khz, 1000000)); +} + void mlx4_en_init_timestamp(struct mlx4_en_dev *mdev) { struct mlx4_dev *dev = mdev->dev; @@ -119,12 +137,7 @@ void mlx4_en_init_timestamp(struct mlx4_en_dev *mdev) memset(&mdev->cycles, 0, sizeof(mdev->cycles)); mdev->cycles.read = mlx4_en_read_clock; mdev->cycles.mask = CLOCKSOURCE_MASK(48); - /* Using shift to make calculation more accurate. Since current HW - * clock frequency is 427 MHz, and cycles are given using a 48 bits - * register, the biggest shift when calculating using u64, is 14 - * (max_cycles * multiplier < 2^64) - */ - mdev->cycles.shift = 14; + mdev->cycles.shift = freq_to_shift(dev->caps.hca_core_clock); mdev->cycles.mult = clocksource_khz2mult(1000 * dev->caps.hca_core_clock, mdev->cycles.shift);