From patchwork Fri Feb 28 09:56:50 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lokesh Vutla X-Patchwork-Id: 11411949 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9D9C71395 for ; Fri, 28 Feb 2020 09:58:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7DE10246A2 for ; Fri, 28 Feb 2020 09:58:17 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ti.com header.i=@ti.com header.b="K2mPTRRA" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726996AbgB1J6J (ORCPT ); Fri, 28 Feb 2020 04:58:09 -0500 Received: from lelv0142.ext.ti.com ([198.47.23.249]:46494 "EHLO lelv0142.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726738AbgB1J6I (ORCPT ); Fri, 28 Feb 2020 04:58:08 -0500 Received: from fllv0034.itg.ti.com ([10.64.40.246]) by lelv0142.ext.ti.com (8.15.2/8.15.2) with ESMTP id 01S9w3iC095067; Fri, 28 Feb 2020 03:58:03 -0600 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ti.com; s=ti-com-17Q1; t=1582883883; bh=atG7ZfBENDR9tsHq2w6d1YPKpXiscCUHT5y2NwfJX74=; h=From:To:CC:Subject:Date:In-Reply-To:References; b=K2mPTRRAPBuESFRCK7ytTKUEFYMBp9UG71ty2mN5Ohn8n6OG0ow43lcxEYPwlK4j8 oPfOnsZWYS3TudaNFAOGQP15wE312BVDMhBI7A3rHUPeo/e/7yf6lMLuJoh744Z20P zreq29MUK8ZBhzCJAyszCUfzbRNxsjH0RX4NZ/pw= Received: from DLEE108.ent.ti.com (dlee108.ent.ti.com [157.170.170.38]) by fllv0034.itg.ti.com (8.15.2/8.15.2) with ESMTPS id 01S9w3JR029677 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=FAIL); Fri, 28 Feb 2020 03:58:03 -0600 Received: from DLEE107.ent.ti.com (157.170.170.37) by DLEE108.ent.ti.com (157.170.170.38) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1847.3; Fri, 28 Feb 2020 03:58:02 -0600 Received: from localhost.localdomain (10.64.41.19) by DLEE107.ent.ti.com (157.170.170.37) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1847.3 via Frontend Transport; Fri, 28 Feb 2020 03:58:02 -0600 Received: from uda0131933.dhcp.ti.com (ileax41-snat.itg.ti.com [10.172.224.153]) by localhost.localdomain (8.15.2/8.15.2) with ESMTP id 01S9vhLJ115767; Fri, 28 Feb 2020 03:57:59 -0600 From: Lokesh Vutla To: Thierry Reding , =?utf-8?q?Uwe_Kleine-K=C3=B6n?= =?utf-8?q?ig?= CC: Tony Lindgren , Linux OMAP Mailing List , , , Sekhar Nori , Vignesh R , Lokesh Vutla Subject: [PATCH v2 5/6] pwm: omap-dmtimer: Do not disable pwm before changing period/duty_cycle Date: Fri, 28 Feb 2020 15:26:50 +0530 Message-ID: <20200228095651.32464-6-lokeshvutla@ti.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20200228095651.32464-1-lokeshvutla@ti.com> References: <20200228095651.32464-1-lokeshvutla@ti.com> MIME-Version: 1.0 X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Sender: linux-omap-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-omap@vger.kernel.org Only the Timer control register(TCLR) cannot be updated when the timer is running. Registers like Counter register(TCRR), loader register(TLDR), match register(TMAR) can be updated when the counter is running. Since TCLR is not updated in pwm_omap_dmtimer_config(), do not stop the timer for period/duty_cycle update. Signed-off-by: Lokesh Vutla Tested-by: Tony Lindgren --- drivers/pwm/pwm-omap-dmtimer.c | 23 +++++++++-------------- 1 file changed, 9 insertions(+), 14 deletions(-) diff --git a/drivers/pwm/pwm-omap-dmtimer.c b/drivers/pwm/pwm-omap-dmtimer.c index 89b3c25d02b8..e7487ceed0a3 100644 --- a/drivers/pwm/pwm-omap-dmtimer.c +++ b/drivers/pwm/pwm-omap-dmtimer.c @@ -15,6 +15,15 @@ * reloaded with the load value and the pwm output goes up. * When counter matches with match register, the output goes down. * Reference Manual: http://www.ti.com/lit/ug/spruh73q/spruh73q.pdf + * + * Limitations: + * - When PWM is running and changing both duty cycle and period, + * we cannot prevent in software that the output might produce + * a period with mixed settings. Especially when period/duty_cyle + * is updated while the pwm pin is high, current pwm period/duty_cycle + * can get updated as below based on the current timer counter: + * - period for current cycle = current_period + new period + * - duty_cycle for current period = current period + new duty_cycle. */ #include @@ -115,7 +124,6 @@ static int pwm_omap_dmtimer_config(struct pwm_chip *chip, u32 load_value, match_value; struct clk *fclk; unsigned long clk_rate; - bool timer_active; dev_dbg(chip->dev, "requested duty cycle: %d ns, period: %d ns\n", duty_ns, period_ns); @@ -191,25 +199,12 @@ static int pwm_omap_dmtimer_config(struct pwm_chip *chip, load_value = (DM_TIMER_MAX - period_cycles) + 1; match_value = load_value + duty_cycles - 1; - /* - * We MUST stop the associated dual-mode timer before attempting to - * write its registers, but calls to omap_dm_timer_start/stop must - * be balanced so check if timer is active before calling timer_stop. - */ - timer_active = pm_runtime_active(&omap->dm_timer_pdev->dev); - if (timer_active) - omap->pdata->stop(omap->dm_timer); - omap->pdata->set_load(omap->dm_timer, load_value); omap->pdata->set_match(omap->dm_timer, true, match_value); dev_dbg(chip->dev, "load value: %#08x (%d), match value: %#08x (%d)\n", load_value, load_value, match_value, match_value); - /* If config was called while timer was running it must be reenabled. */ - if (timer_active) - pwm_omap_dmtimer_start(omap); - mutex_unlock(&omap->mutex); return 0;