From mboxrd@z Thu Jan 1 00:00:00 1970 From: Philipp Zabel Subject: Re: [PATCH v2] clk: Add PWM clock driver Date: Tue, 09 Dec 2014 10:15:33 +0100 Message-ID: <1418116533.3107.1.camel@pengutronix.de> References: <1415007078-7947-1-git-send-email-p.zabel@pengutronix.de> <5480A132.2010103@elproma.com.pl> <54860426.3020400@elproma.com.pl> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <54860426.3020400-9tnw74Q4ehaHKKo6LODCOg@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Janusz =?UTF-8?Q?U=C5=BCycki?= Cc: Mike Turquette , Thierry Reding , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-pwm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: devicetree@vger.kernel.org Hi Janusz, Am Montag, den 08.12.2014, 21:03 +0100 schrieb Janusz U=C5=BCycki: > Hi, >=20 > I've fixed my pwm driver and I can enable 12MHz 50% output using sysf= s.=20 > Then I rebased the pwm-clock to 3.14. > I have connected mcp2515 and it works with fixed clock. When I switch= =20 > the chip's clock to pwm clock in dt > I get "mcp251x: probe of spi1.2 failed with error -2". I've also adde= d=20 > clock-frequency property > but it didn't help. > When I set the mcp2515 clock to fixed clock again but the clock is no= t=20 > 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 =3D <1>; > #size-cells =3D <1>; > ranges; > mcp251x_xtal_clk: mcp2515_xtal { > compatible =3D "fixed-clock"; > #clock-cells =3D <0>; > clock-frequency =3D <12000000>; > }; >=20 > mcp251x_pwm_clk: mcp2515_pwm { > compatible =3D "pwm-clock"; > #clock-cells =3D <0>; > clock-frequency =3D <12000000>; > clock-output-names =3D "can_clk"; > pwms =3D <&pwm 3 83>; /* 12MHz =3D 1 / ~= 83ns */ > }; > }; >=20 > 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 lik= e > 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; =20 pwm =3D 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); + } =20 ret =3D 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; + } =20 init.name =3D "pwm-clock"; init.ops =3D &clk_pwm_ops; @@ -78,11 +82,18 @@ int clk_pwm_probe(struct platform_device *pdev) clk_pwm->pwm =3D pwm; clk_pwm->hw.init =3D &init; clk =3D 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); + } =20 - return of_clk_add_provider(pdev->dev.of_node, - of_clk_src_simple_get, clk); + ret =3D 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; } =20 int clk_pwm_remove(struct platform_device *pdev) -- To unsubscribe from this list: send the line "unsubscribe devicetree" i= n the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html