Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756164AbaLIJPu (ORCPT ); Tue, 9 Dec 2014 04:15:50 -0500 Received: from metis.ext.pengutronix.de ([92.198.50.35]:60845 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754248AbaLIJPp (ORCPT ); Tue, 9 Dec 2014 04:15:45 -0500 Message-ID: <1418116533.3107.1.camel@pengutronix.de> Subject: Re: [PATCH v2] clk: Add PWM clock driver From: Philipp Zabel To: Janusz =?UTF-8?Q?U=C5=BCycki?= Cc: Mike Turquette , Thierry Reding , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pwm@vger.kernel.org Date: Tue, 09 Dec 2014 10:15:33 +0100 In-Reply-To: <54860426.3020400@elproma.com.pl> References: <1415007078-7947-1-git-send-email-p.zabel@pengutronix.de> <5480A132.2010103@elproma.com.pl> <54860426.3020400@elproma.com.pl> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.7-1 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 2001:67c:670:100:96de:80ff:fec2:9969 X-SA-Exim-Mail-From: p.zabel@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Janusz, Am Montag, den 08.12.2014, 21:03 +0100 schrieb Janusz Użycki: > Hi, > > I've fixed my pwm driver and I can enable 12MHz 50% output using sysfs. > Then I rebased the pwm-clock to 3.14. > I have connected mcp2515 and it works with fixed clock. When I switch > the chip's clock to pwm clock in dt > I get "mcp251x: probe of spi1.2 failed with error -2". I've also added > clock-frequency property > but it didn't help. > When I set the mcp2515 clock to fixed clock again but the clock is not > applied to mcp2515 I get > "mcp251x spi1.2: MCP251x didn't enter in conf mode after reset". > So it looks this is indeed probe error caused likely by dt. Did pwm-clock fail to probe already? Could you check with the patch below? > The fixed and pwm clock in DT: > clocks { > #address-cells = <1>; > #size-cells = <1>; > ranges; > mcp251x_xtal_clk: mcp2515_xtal { > compatible = "fixed-clock"; > #clock-cells = <0>; > clock-frequency = <12000000>; > }; > > mcp251x_pwm_clk: mcp2515_pwm { > compatible = "pwm-clock"; > #clock-cells = <0>; > clock-frequency = <12000000>; > clock-output-names = "can_clk"; > pwms = <&pwm 3 83>; /* 12MHz = 1 / ~83ns */ > }; > }; > > Also the mentioned frequency recalculation problem appears here. > In the case above recalc value is about 12.048MHz instead of 12.0MHz. > While PWM block is clocked 24MHz and the pwm generates exactly 12MHz > the pwm-clock driver returns drifted value. Using clock-frequency like > fixed-clock does could simply solve the binding problem. Yes, for this case it is very unfortunate that there's only nanosecond resolution for the duty cycle. Adding a clock-frequency property to indicate the real frequency would solve this problem. ------8<------ diff --git a/drivers/clk/clk-pwm.c b/drivers/clk/clk-pwm.c index 8f747b3..9c13856 100644 --- a/drivers/clk/clk-pwm.c +++ b/drivers/clk/clk-pwm.c @@ -63,12 +63,16 @@ int clk_pwm_probe(struct platform_device *pdev) return -ENOMEM; pwm = devm_pwm_get(&pdev->dev, NULL); - if (IS_ERR(pwm)) + if (IS_ERR(pwm)) { + dev_err(&pdev->dev, "failed to get pwm: %ld\n", PTR_ERR(pwm)); return PTR_ERR(pwm); + } ret = pwm_config(pwm, (pwm->period + 1) >> 1, pwm->period); - if (ret < 0) + if (ret < 0) { + dev_err(&pdev->dev, "failed to configure pwm: %d\n", ret); return ret; + } init.name = "pwm-clock"; init.ops = &clk_pwm_ops; @@ -78,11 +82,18 @@ int clk_pwm_probe(struct platform_device *pdev) clk_pwm->pwm = pwm; clk_pwm->hw.init = &init; clk = devm_clk_register(&pdev->dev, &clk_pwm->hw); - if (IS_ERR(clk)) + if (IS_ERR(clk)) { + dev_err(&pdev->dev, "failed to register clock: %ld\n", + PTR_ERR(clk)); return PTR_ERR(clk); + } - return of_clk_add_provider(pdev->dev.of_node, - of_clk_src_simple_get, clk); + ret = of_clk_add_provider(pdev->dev.of_node, + of_clk_src_simple_get, clk); + if (ret) + dev_err(&pdev->dev, "failed to add clock provider: %d\n", ret); + + return ret; } int clk_pwm_remove(struct platform_device *pdev) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/