From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1162931AbdAJR2l (ORCPT ); Tue, 10 Jan 2017 12:28:41 -0500 Received: from mail.kmu-office.ch ([178.209.48.109]:45119 "EHLO mail.kmu-office.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1031551AbdAJR2j (ORCPT ); Tue, 10 Jan 2017 12:28:39 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Date: Tue, 10 Jan 2017 09:28:36 -0800 From: Stefan Agner To: Lukasz Majewski , Boris Brezillon Cc: Thierry Reding , Sascha Hauer , linux-pwm@vger.kernel.org, Bhuvanchandra DV , linux-kernel@vger.kernel.org, Lothar Wassmann , kernel@pengutronix.de, Fabio Estevam , Philipp Zabel Subject: Re: [PATCH v4 02/11] pwm: imx: remove ipg clock and enable per clock when required In-Reply-To: <1483573014-13185-3-git-send-email-lukma@denx.de> References: <1483573014-13185-1-git-send-email-lukma@denx.de> <1483573014-13185-3-git-send-email-lukma@denx.de> Message-ID: <07eb3b937691011ee3138cd4cf5835d0@agner.ch> User-Agent: Roundcube Webmail/1.1.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2017-01-04 15:36, Lukasz Majewski wrote: > From: Boris Brezillon > > The use of the ipg clock was introduced with commit 7b27c160c681 > ("pwm: i.MX: fix clock lookup"). > In the commit message it was claimed that the ipg clock is enabled for > register accesses. This is true for the ->config() callback, but not > for the ->set_enable() callback. Given that the ipg clock is not > consistently enabled for all register accesses we can assume that either > it is not required at all or that the current code does not work. > Remove the ipg clock code for now so that it's no longer in the way of > refactoring the driver. > > In the other hand, the imx7 IP requires the peripheral clock to be Nit: s/In/On? > enabled before accessing its registers. Since ->config() can be called > when the PWM is disabled (in which case, the peripheral clock is also > disabled), we need to surround the imx->config() with > clk_prepare_enable(per_clk)/clk_disable_unprepare(per_clk) calls. > > Note that the imx7 IP was working fine so far because the ipg clock was > actually pointing to the peripheral clock, which guaranteed peripheral > clock activation even when ->config() was called when the PWM was > disabled. That is not entirely true, but almost, I would say: "Note that the driver was working fine for the i.MX 7 IP so far because the ipg and peripheral clock use the same hardware clock gate, which guaranteed..." > > Signed-off-by: Sascha Hauer > Signed-off-by: Boris Brezillon > Cc: Philipp Zabel Reviewed-by: Stefan Agner Tried on-top of 4.10-rc3, only this patch, still works. Tested-by: Stefan Agner -- Stefan > --- > Changes in v4: > - Enable per clk before calling imx->config() > > Changes in v3: > - New patch > --- > drivers/pwm/pwm-imx.c | 12 ++---------- > 1 file changed, 2 insertions(+), 10 deletions(-) > > diff --git a/drivers/pwm/pwm-imx.c b/drivers/pwm/pwm-imx.c > index d600fd5..b1d1e50 100644 > --- a/drivers/pwm/pwm-imx.c > +++ b/drivers/pwm/pwm-imx.c > @@ -49,7 +49,6 @@ > > struct imx_chip { > struct clk *clk_per; > - struct clk *clk_ipg; > > void __iomem *mmio_base; > > @@ -206,13 +205,13 @@ static int imx_pwm_config(struct pwm_chip *chip, > struct imx_chip *imx = to_imx_chip(chip); > int ret; > > - ret = clk_prepare_enable(imx->clk_ipg); > + ret = clk_prepare_enable(imx->clk_per); > if (ret) > return ret; > > ret = imx->config(chip, pwm, duty_ns, period_ns); > > - clk_disable_unprepare(imx->clk_ipg); > + clk_disable_unprepare(imx->clk_per); > > return ret; > } > @@ -293,13 +292,6 @@ static int imx_pwm_probe(struct platform_device *pdev) > return PTR_ERR(imx->clk_per); > } > > - imx->clk_ipg = devm_clk_get(&pdev->dev, "ipg"); > - if (IS_ERR(imx->clk_ipg)) { > - dev_err(&pdev->dev, "getting ipg clock failed with %ld\n", > - PTR_ERR(imx->clk_ipg)); > - return PTR_ERR(imx->clk_ipg); > - } > - > imx->chip.ops = &imx_pwm_ops; > imx->chip.dev = &pdev->dev; > imx->chip.base = -1;