From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 66768178381; Tue, 2 Jul 2024 17:07:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719940026; cv=none; b=o3M8XKRHqyTn3yjyM38wJPRdU2RehtvSKZOAO5k9FRuvAFKR1c+6YglONq/sOiPlr8iSanPdPE80mJprWyPXx2XoQ9Dksp8vck58dAaRB/fdxdzie66Ox0TgHT5bqSj8VOqHcqIdZh8njCMDswp3jVghVTfDm2pRzQxHIQ7k2xU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719940026; c=relaxed/simple; bh=89hjCFzK5SJ2eKc6wj7v9sJJljp5m1JcHG8z995VQWU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=QtZ7McBPN1M0zs7sVaQhraPKBzT6320sLQwRx9sRZy1d43TLD3/WHvftq8fKborlvAo90RtHhnhmk5js3G6baQ9NeNCg7fUoCeAaH6dM01082fnrdGyapWm5GGIBvnFQg3QFcvaS5uNe2veGjQBr9zlpZ/FtxjzKZ+ccKMQwzL4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=sRm8wnIJ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="sRm8wnIJ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E17D4C4AF0A; Tue, 2 Jul 2024 17:07:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1719940026; bh=89hjCFzK5SJ2eKc6wj7v9sJJljp5m1JcHG8z995VQWU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=sRm8wnIJEI1UhIUcjAQ2a09iuKxi+SySUZT7G77Bva1CbytlMbktrCZBMW64lH1ho 7DQ86G+fVnBqRfk+N1q9oNB39uPDtujHQOMZq8kvYxjZruH9KuRQ6f+78IxA70Lins KHnmYMwVHxZskKW2nEWQR/w60xQc+NqqTIMiUQVU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= , Sasha Levin Subject: [PATCH 6.9 013/222] pwm: stm32: Calculate prescaler with a division instead of a loop Date: Tue, 2 Jul 2024 19:00:51 +0200 Message-ID: <20240702170244.481308773@linuxfoundation.org> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240702170243.963426416@linuxfoundation.org> References: <20240702170243.963426416@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Uwe Kleine-König [ Upstream commit 8002fbeef1e469b2c397d5cd2940e37b32a17849 ] Instead of looping over increasing values for the prescaler and testing if it's big enough, calculate the value using a single division. Link: https://lore.kernel.org/r/498a44b313a6c0a84ccddd03cd67aadaaaf7daf2.1710711976.git.u.kleine-koenig@pengutronix.de Signed-off-by: Uwe Kleine-König Stable-dep-of: c45fcf46ca23 ("pwm: stm32: Refuse too small period requests") Signed-off-by: Sasha Levin --- drivers/pwm/pwm-stm32.c | 30 +++++++++++++++++------------- 1 file changed, 17 insertions(+), 13 deletions(-) diff --git a/drivers/pwm/pwm-stm32.c b/drivers/pwm/pwm-stm32.c index 27fcc90504f67..1c8911353b81d 100644 --- a/drivers/pwm/pwm-stm32.c +++ b/drivers/pwm/pwm-stm32.c @@ -311,29 +311,33 @@ static int stm32_pwm_capture(struct pwm_chip *chip, struct pwm_device *pwm, static int stm32_pwm_config(struct stm32_pwm *priv, unsigned int ch, u64 duty_ns, u64 period_ns) { - unsigned long long prd, div, dty; - unsigned int prescaler = 0; + unsigned long long prd, dty; + unsigned long long prescaler; u32 ccmr, mask, shift; /* * .probe() asserted that clk_get_rate() is not bigger than 1 GHz, so - * this won't overflow. + * the calculations here won't overflow. + * First we need to find the minimal value for prescaler such that + * + * period_ns * clkrate + * ------------------------------ + * NSEC_PER_SEC * (prescaler + 1) + * + * isn't bigger than max_arr. */ - div = mul_u64_u64_div_u64(period_ns, clk_get_rate(priv->clk), - NSEC_PER_SEC); - prd = div; - - while (div > priv->max_arr) { - prescaler++; - div = prd; - do_div(div, prescaler + 1); - } - prd = div; + prescaler = mul_u64_u64_div_u64(period_ns, clk_get_rate(priv->clk), + (u64)NSEC_PER_SEC * priv->max_arr); + if (prescaler > 0) + prescaler -= 1; if (prescaler > MAX_TIM_PSC) return -EINVAL; + prd = mul_u64_u64_div_u64(period_ns, clk_get_rate(priv->clk), + (u64)NSEC_PER_SEC * (prescaler + 1)); + /* * All channels share the same prescaler and counter so when two * channels are active at the same time we can't change them -- 2.43.0