From patchwork Fri Oct 4 13:32:06 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Rasmus Villemoes X-Patchwork-Id: 1171853 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=rasmusvillemoes.dk Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=rasmusvillemoes.dk header.i=@rasmusvillemoes.dk header.b="cVOCOZBf"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 46l9mw6gv6z9sRN for ; Fri, 4 Oct 2019 23:33:20 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388682AbfJDNdI (ORCPT ); Fri, 4 Oct 2019 09:33:08 -0400 Received: from mail-lj1-f195.google.com ([209.85.208.195]:38552 "EHLO mail-lj1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388667AbfJDNdI (ORCPT ); Fri, 4 Oct 2019 09:33:08 -0400 Received: by mail-lj1-f195.google.com with SMTP id b20so6543058ljj.5 for ; Fri, 04 Oct 2019 06:33:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rasmusvillemoes.dk; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=enjD7GinjPEmXbD794v1TL8qB8AXAn8TuqNGVlImRwo=; b=cVOCOZBfFV4/Q55ikZfbm3e6RfV3oQtgU+vNCBrhPnWHW0yMoE/YOhCTLpEuSkzPyt p/jSR/BxvhMiDKgCkwbGaaribeHJHsoJnVzAtd0w3FmfMc8fEw6xUkR16/spC40jUK7j aqmMH79uB6vD7zvJf5xhJIjmux8oZvPGm4juI= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=enjD7GinjPEmXbD794v1TL8qB8AXAn8TuqNGVlImRwo=; b=IcMO0KJk3mbFNxhhBR1I4Agrx7n0CbiN7C7BNILGdcCr6yqFh8EGKrtf9nWMZgTALb Tk2H0/ufBTEH1iPRUzT4vxmFFR51wg1eVfIdsqBrEkTzLAG7YpTGBC3dpK4jSksAzHn4 ZTrIWCu6WQJJvzCsKmUM0VAji+PIlHZzldLnlnVllKc01Ve02ffnIetEEarbs5zZj6SD l/QFy6vdo+kiOJclNmRzimPNWZoxjZJVNW/DkSG+tR1dq3JrMlpR1OcpgftvVc0+QftI AKCR78eYI3+kfyvNUuUvKb0IIwG/4oodapAiJF6BuOVA+VvjXmyqOZi4pg8S7ind//Ws MMfg== X-Gm-Message-State: APjAAAVLCrvGT96x9EGXOGWeYyYywOwWRO0ZuhEG1vwAoQPa0Bx46ylq UqB+jvjzBpyKJzq5ZyIO3HubNA== X-Google-Smtp-Source: APXvYqzZiPqBZ6nH+PAoIMx4rztRtbFWWqjLzLXZv4d3HV/oeGtcTwju/gptKDUYmHusErUAOSz6bA== X-Received: by 2002:a2e:9585:: with SMTP id w5mr3871975ljh.220.1570195985888; Fri, 04 Oct 2019 06:33:05 -0700 (PDT) Received: from prevas-ravi.prevas.se ([81.216.59.226]) by smtp.gmail.com with ESMTPSA id y26sm1534991ljj.90.2019.10.04.06.33.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Oct 2019 06:33:05 -0700 (PDT) From: Rasmus Villemoes To: Thierry Reding , =?utf-8?q?Uwe_Kleine-K?= =?utf-8?b?w7ZuaWc=?= , Shawn Guo , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , NXP Linux Team Cc: devicetree@vger.kernel.org, Rob Herring , Rasmus Villemoes , linux-pwm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 5/6] pwm: mxs: avoid a division in mxs_pwm_apply() Date: Fri, 4 Oct 2019 15:32:06 +0200 Message-Id: <20191004133207.6663-6-linux@rasmusvillemoes.dk> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191004133207.6663-1-linux@rasmusvillemoes.dk> References: <20191004133207.6663-1-linux@rasmusvillemoes.dk> MIME-Version: 1.0 Sender: linux-pwm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pwm@vger.kernel.org Since the divisor is not a compile-time constant (unless gcc somehow decided to unroll the loop PERIOD_CDIV_MAX times), this does a somewhat expensive 32/32 division. Replace that with a right shift. We still have a 64/32 division just below, but at least in that case the divisor is compile-time constant. Signed-off-by: Rasmus Villemoes Reviewed-by: Uwe Kleine-König --- drivers/pwm/pwm-mxs.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/pwm/pwm-mxs.c b/drivers/pwm/pwm-mxs.c index 57562221c439..f2e57fcf8f8b 100644 --- a/drivers/pwm/pwm-mxs.c +++ b/drivers/pwm/pwm-mxs.c @@ -33,8 +33,8 @@ #define PERIOD_CDIV(div) (((div) & 0x7) << 20) #define PERIOD_CDIV_MAX 8 -static const unsigned int cdiv[PERIOD_CDIV_MAX] = { - 1, 2, 4, 8, 16, 64, 256, 1024 +static const u8 cdiv_shift[PERIOD_CDIV_MAX] = { + 0, 1, 2, 3, 4, 6, 8, 10 }; struct mxs_pwm_chip { @@ -71,7 +71,7 @@ static int mxs_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, rate = clk_get_rate(mxs->clk); while (1) { - c = rate / cdiv[div]; + c = rate >> cdiv_shift[div]; c = c * state->period; do_div(c, 1000000000); if (c < PERIOD_PERIOD_MAX)