From patchwork Wed Jan 9 08:19:08 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Yoshihiro Shimoda X-Patchwork-Id: 1022318 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-pwm-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=renesas.com Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 43ZMYS68bsz9sML for ; Wed, 9 Jan 2019 19:22:04 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729860AbfAIIWC (ORCPT ); Wed, 9 Jan 2019 03:22:02 -0500 Received: from relmlor1.renesas.com ([210.160.252.171]:21720 "EHLO relmlie5.idc.renesas.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729334AbfAIIWC (ORCPT ); Wed, 9 Jan 2019 03:22:02 -0500 X-IronPort-AV: E=Sophos;i="5.56,456,1539615600"; d="scan'208";a="4746206" Received: from unknown (HELO relmlir6.idc.renesas.com) ([10.200.68.152]) by relmlie5.idc.renesas.com with ESMTP; 09 Jan 2019 17:21:58 +0900 Received: from localhost.localdomain (unknown [10.166.17.210]) by relmlir6.idc.renesas.com (Postfix) with ESMTP id 388B9445EBAC; Wed, 9 Jan 2019 17:21:58 +0900 (JST) From: Yoshihiro Shimoda To: thierry.reding@gmail.com Cc: linux-pwm@vger.kernel.org, linux-renesas-soc@vger.kernel.org, Yoshihiro Shimoda Subject: [PATCH v3 4/4] pwm: rcar: improve calculation of divider Date: Wed, 9 Jan 2019 17:19:08 +0900 Message-Id: <1547021948-7664-5-git-send-email-yoshihiro.shimoda.uh@renesas.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1547021948-7664-1-git-send-email-yoshihiro.shimoda.uh@renesas.com> References: <1547021948-7664-1-git-send-email-yoshihiro.shimoda.uh@renesas.com> MIME-Version: 1.0 Sender: linux-pwm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pwm@vger.kernel.org The rcar_pwm_get_clock_division() has a loop to calculate the divider, but the value of div should be calculatable without a loop. So, this patch improves it. This algorithm is suggested by Uwe Kleine-König and Laurent Pinchart. Signed-off-by: Yoshihiro Shimoda Acked-by: Uwe Kleine-König --- drivers/pwm/pwm-rcar.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/drivers/pwm/pwm-rcar.c b/drivers/pwm/pwm-rcar.c index 1e13fbb..cfe7dd1 100644 --- a/drivers/pwm/pwm-rcar.c +++ b/drivers/pwm/pwm-rcar.c @@ -8,6 +8,8 @@ #include #include #include +#include +#include #include #include #include @@ -68,19 +70,15 @@ static void rcar_pwm_update(struct rcar_pwm_chip *rp, u32 mask, u32 data, static int rcar_pwm_get_clock_division(struct rcar_pwm_chip *rp, int period_ns) { unsigned long clk_rate = clk_get_rate(rp->clk); - unsigned long long max; /* max cycle / nanoseconds */ - unsigned int div; + u64 div, tmp; if (clk_rate == 0) return -EINVAL; - for (div = 0; div <= RCAR_PWM_MAX_DIVISION; div++) { - max = (unsigned long long)NSEC_PER_SEC * RCAR_PWM_MAX_CYCLE * - (1 << div); - do_div(max, clk_rate); - if (period_ns <= max) - break; - } + div = (u64)NSEC_PER_SEC * RCAR_PWM_MAX_CYCLE; + tmp = (u64)period_ns * clk_rate + div - 1; + tmp = div64_u64(tmp, div); + div = ilog2(tmp - 1) + 1; return (div <= RCAR_PWM_MAX_DIVISION) ? div : -ERANGE; }