From patchwork Mon Aug 24 12:01:18 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hans de Goede X-Patchwork-Id: 251718 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A06ACC433EB for ; Mon, 24 Aug 2020 12:02:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7C6F7207D3 for ; Mon, 24 Aug 2020 12:02:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="YetcYC+R" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727030AbgHXMCI (ORCPT ); Mon, 24 Aug 2020 08:02:08 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:20284 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727039AbgHXMCH (ORCPT ); Mon, 24 Aug 2020 08:02:07 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1598270526; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=yf1u7UBfto7CRYFZUxDmMudYk5P2tT4SCbGumU5AATw=; b=YetcYC+RBQ/09K3xgZ4xUh6PqWFbk/p1Sur14M1q9nwJtyZLa89XszN4SnW5aUTny5B2cO JfSYxXHbTR0ZpBKtSwGrhEeCYeYsEbozqW4AnavdCfDFwp0cSmpQ+uqfAYy8FZwi9QHf00 DuUvuEH5fXAwg3JeSAZlNJ8j48LUvDU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-148-j-QlUsLHNS-1EuILJjXbiA-1; Mon, 24 Aug 2020 08:02:03 -0400 X-MC-Unique: j-QlUsLHNS-1EuILJjXbiA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DC08F801AE1; Mon, 24 Aug 2020 12:02:01 +0000 (UTC) Received: from x1.localdomain.com (ovpn-113-147.ams2.redhat.com [10.36.113.147]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5ED495D9DD; Mon, 24 Aug 2020 12:01:58 +0000 (UTC) From: Hans de Goede To: Thierry Reding , =?utf-8?q?Uwe_Kleine-K?= =?utf-8?b?w7ZuaWc=?= , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , =?utf-8?b?VmlsbGUgU3lyasOkbMOk?= , "Rafael J . Wysocki" , Len Brown Cc: Hans de Goede , linux-pwm@vger.kernel.org, intel-gfx , dri-devel@lists.freedesktop.org, Andy Shevchenko , Mika Westerberg , linux-acpi@vger.kernel.org Subject: [PATCH v6 08/16] pwm: crc: Fix off-by-one error in the clock-divider calculations Date: Mon, 24 Aug 2020 14:01:18 +0200 Message-Id: <20200824120126.7116-9-hdegoede@redhat.com> In-Reply-To: <20200824120126.7116-1-hdegoede@redhat.com> References: <20200824120126.7116-1-hdegoede@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org The CRC PWM controller has a clock-divider which divides the clock with a value between 1-128. But as can seen from the PWM_DIV_CLK_xxx defines, this range maps to a register value of 0-127. So after calculating the clock-divider we must subtract 1 to get the register value, unless the requested frequency was so high that the calculation has already resulted in a (rounded) divider value of 0. Note that before this fix, setting a period of PWM_MAX_PERIOD_NS which corresponds to the max. divider value of 128 could have resulted in a bug where the code would use 128 as divider-register value which would have resulted in an actual divider value of 0 (and the enable bit being set). A rounding error stopped this bug from actually happen. This same rounding error means that after the subtraction of 1 it is impossible to set the divider to 128. Also bump PWM_MAX_PERIOD_NS by 1 ns to allow setting a divider of 128 (register-value 127). Reviewed-by: Andy Shevchenko Signed-off-by: Hans de Goede --- Changes in v3: - Introduce crc_pwm_calc_clk_div() here instead of later in the patch-set to reduce the amount of churn in the patch-set a bit --- drivers/pwm/pwm-crc.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/drivers/pwm/pwm-crc.c b/drivers/pwm/pwm-crc.c index c056eb9b858c..44ec7d5b63e1 100644 --- a/drivers/pwm/pwm-crc.c +++ b/drivers/pwm/pwm-crc.c @@ -22,7 +22,7 @@ #define PWM_MAX_LEVEL 0xFF #define PWM_BASE_CLK_MHZ 6 /* 6 MHz */ -#define PWM_MAX_PERIOD_NS 5461333 /* 183 Hz */ +#define PWM_MAX_PERIOD_NS 5461334 /* 183 Hz */ /** * struct crystalcove_pwm - Crystal Cove PWM controller @@ -39,6 +39,18 @@ static inline struct crystalcove_pwm *to_crc_pwm(struct pwm_chip *pc) return container_of(pc, struct crystalcove_pwm, chip); } +static int crc_pwm_calc_clk_div(int period_ns) +{ + int clk_div; + + clk_div = PWM_BASE_CLK_MHZ * period_ns / (256 * NSEC_PER_USEC); + /* clk_div 1 - 128, maps to register values 0-127 */ + if (clk_div > 0) + clk_div--; + + return clk_div; +} + static int crc_pwm_enable(struct pwm_chip *c, struct pwm_device *pwm) { struct crystalcove_pwm *crc_pwm = to_crc_pwm(c); @@ -68,11 +80,10 @@ static int crc_pwm_config(struct pwm_chip *c, struct pwm_device *pwm, } if (pwm_get_period(pwm) != period_ns) { - int clk_div; + int clk_div = crc_pwm_calc_clk_div(period_ns); /* changing the clk divisor, need to disable fisrt */ crc_pwm_disable(c, pwm); - clk_div = PWM_BASE_CLK_MHZ * period_ns / (256 * NSEC_PER_USEC); regmap_write(crc_pwm->regmap, PWM0_CLK_DIV, clk_div | PWM_OUTPUT_ENABLE);