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[209.132.180.67]) by mx.google.com with ESMTP id f11si4822525plm.77.2017.12.15.00.53.16; Fri, 15 Dec 2017 00:53:17 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@linaro.org header.s=google header.b=H8MfPQhI; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linaro.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754887AbdLOIxP (ORCPT + 20 others); Fri, 15 Dec 2017 03:53:15 -0500 Received: from mail-wm0-f66.google.com ([74.125.82.66]:45521 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753622AbdLOIxL (ORCPT ); Fri, 15 Dec 2017 03:53:11 -0500 Received: by mail-wm0-f66.google.com with SMTP id 9so15922105wme.4 for ; Fri, 15 Dec 2017 00:53:10 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=7UYSmJ//9Mfom7wNt9+xW9mt5SqRdz1LBQvLuanRgz0=; b=H8MfPQhIj0f7Q3kSiaGLwur9RaQ+bVA/5/8ZCOUzf5mDnEyyZekYhB349AEeug9yHB 88f9t3RlYt3ohcrQ1EvKPWCmGNqhXw2UzTJ7d3+gAvm42tIbnpOKYlRt24CZRV2jBUUZ sh/qK5UHdWkas4vY99GdLKjr0sIdigoZjHuZI= 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; bh=7UYSmJ//9Mfom7wNt9+xW9mt5SqRdz1LBQvLuanRgz0=; b=Ak29pQqQVkepbcKcCh3CMMJ/fX2ZAcRtGyMahW20eBOkaAwpELvAZUnU7kAVEQy/gQ SIjFVOMqq+eK6s3fGYSIE2d9XuXOd2Rwa13hC7KtuhlFAyMEYPEvktmwoHqCXnt/FzDE TmRJ8IQJfvA6Wqxco29Q3upbDK1W7C9mBx9LwFF8N+bfFjjI6LcB+HpNhXD9mXamvQ1T EvtiGSLadzPACNEKgyjculFKnKgTNdb7aem1lBQF7pi8PTXq1nc5Jg2VBKdOLWF469sc wqwf5xhfrVmjrEjrgIGnwbxoZmfk+M0HbceRfVY7qF9BiAUrpFA068Fg8FwZ2oNev+en xeVQ== X-Gm-Message-State: AKGB3mKEGw6EXm6RUEQqgDIZAN6d7BHRWSW25goouMVKwBooZoIme4W+ xaZn0GdZqIje5nAHpMJNLKYOfQ== X-Received: by 10.28.106.16 with SMTP id f16mr4892031wmc.58.1513327989970; Fri, 15 Dec 2017 00:53:09 -0800 (PST) Received: from lmecxl0911.lme.st.com ([80.215.40.214]) by smtp.gmail.com with ESMTPSA id r14sm3211803wra.71.2017.12.15.00.53.07 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Fri, 15 Dec 2017 00:53:09 -0800 (PST) From: Benjamin Gaignard X-Google-Original-From: Benjamin Gaignard To: mark.rutland@arm.com, linux@armlinux.org.uk, mcoquelin.stm32@gmail.com, alexandre.torgue@st.com, daniel.lezcano@linaro.org, tglx@linutronix.de Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Benjamin Gaignard Subject: [PATCH 2/4] clocksource: stm32: use prescaler to adjust the resolution Date: Fri, 15 Dec 2017 09:52:45 +0100 Message-Id: <20171215085247.14946-3-benjamin.gaignard@st.com> X-Mailer: git-send-email 2.15.0 In-Reply-To: <20171215085247.14946-1-benjamin.gaignard@st.com> References: <20171215085247.14946-1-benjamin.gaignard@st.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Rather than use fixed prescaler values compute it to get a clock as close as possible of 10KHz and a resolution of 0.1ms. Signed-off-by: Benjamin Gaignard --- drivers/clocksource/timer-stm32.c | 23 ++++++++++++++++------- 1 file changed, 16 insertions(+), 7 deletions(-) -- 2.15.0 diff --git a/drivers/clocksource/timer-stm32.c b/drivers/clocksource/timer-stm32.c index 23a321cca45b..de721d318065 100644 --- a/drivers/clocksource/timer-stm32.c +++ b/drivers/clocksource/timer-stm32.c @@ -37,6 +37,11 @@ #define TIM_EGR_UG BIT(0) +#define MAX_TIM_PSC 0xFFFF + +/* Target a 10KHz clock to get a resolution of 0.1 ms */ +#define TARGETED_CLK_RATE 10000 + static int stm32_clock_event_shutdown(struct clock_event_device *evt) { struct timer_of *to = to_timer_of(evt); @@ -83,7 +88,7 @@ static irqreturn_t stm32_clock_event_handler(int irq, void *dev_id) static void __init stm32_clockevent_init(struct timer_of *to) { unsigned long max_delta; - int prescaler; + unsigned long prescaler; to->clkevt.name = "stm32_clockevent"; to->clkevt.features = CLOCK_EVT_FEAT_PERIODIC; @@ -96,13 +101,17 @@ static void __init stm32_clockevent_init(struct timer_of *to) /* Detect whether the timer is 16 or 32 bits */ writel_relaxed(~0U, timer_of_base(to) + TIM_ARR); max_delta = readl_relaxed(timer_of_base(to) + TIM_ARR); - if (max_delta == ~0U) { - prescaler = 1; + to->clkevt.rating = 50; + if (max_delta == ~0U) to->clkevt.rating = 250; - } else { - prescaler = 1024; - to->clkevt.rating = 50; - } + + /* + * Get the highest possible prescaler value to be as close + * as possible of TARGETED_CLK_RATE + */ + prescaler = DIV_ROUND_CLOSEST(timer_of_rate(to), TARGETED_CLK_RATE); + if (prescaler > MAX_TIM_PSC) + prescaler = MAX_TIM_PSC; writel_relaxed(0, timer_of_base(to) + TIM_ARR); writel_relaxed(prescaler - 1, timer_of_base(to) + TIM_PSC);