Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933710AbcJLXYQ (ORCPT ); Wed, 12 Oct 2016 19:24:16 -0400 Received: from mail.kmu-office.ch ([178.209.48.109]:56797 "EHLO mail.kmu-office.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933214AbcJLXYJ (ORCPT ); Wed, 12 Oct 2016 19:24:09 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Date: Wed, 12 Oct 2016 16:18:20 -0700 From: Stefan Agner To: Lukasz Majewski Cc: Bhuvanchandra DV , shawnguo@kernel.org, thierry.reding@gmail.com, robh+dt@kernel.org, mark.rutland@arm.com, kernel@pengutronix.de, fabio.estevam@nxp.com, linux-pwm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Lothar Wassmann , boris.brezillon@free-electrons.com Subject: Re: [PATCH v3 3/6] pwm: imx: support output polarity inversion In-Reply-To: <20161013001540.7f759158@jawa> References: <20161007151129.6043-1-bhuvanchandra.dv@toradex.com> <20161007151129.6043-4-bhuvanchandra.dv@toradex.com> <5325a332099473a2d8382530f79c5a8e@agner.ch> <20161013001540.7f759158@jawa> Message-ID: User-Agent: Roundcube Webmail/1.1.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7746 Lines: 237 On 2016-10-12 15:15, Lukasz Majewski wrote: > Hi Stefan, > >> On 2016-10-07 08:11, Bhuvanchandra DV wrote: >> > From: Lothar Wassmann >> > >> > The i.MX pwm unit on i.MX27 and newer SoCs provides a configurable >> > output polarity. This patch adds support to utilize this feature >> > where available. >> > >> > Signed-off-by: Lothar Waßmann >> > Signed-off-by: Lukasz Majewski >> > Signed-off-by: Bhuvanchandra DV >> > Acked-by: Shawn Guo >> > Reviewed-by: Sascha Hauer >> > --- >> > Documentation/devicetree/bindings/pwm/imx-pwm.txt | 6 +-- >> > drivers/pwm/pwm-imx.c | 51 >> > +++++++++++++++++++++-- 2 files changed, 51 insertions(+), 6 >> > deletions(-) >> > >> > diff --git a/Documentation/devicetree/bindings/pwm/imx-pwm.txt >> > b/Documentation/devicetree/bindings/pwm/imx-pwm.txt >> > index e00c2e9..c61bdf8 100644 >> > --- a/Documentation/devicetree/bindings/pwm/imx-pwm.txt >> > +++ b/Documentation/devicetree/bindings/pwm/imx-pwm.txt >> > @@ -6,8 +6,8 @@ Required properties: >> > - "fsl,imx1-pwm" for PWM compatible with the one integrated on >> > i.MX1 >> > - "fsl,imx27-pwm" for PWM compatible with the one integrated on >> > i.MX27 >> > - reg: physical base address and length of the controller's >> > registers -- #pwm-cells: should be 2. See pwm.txt in this directory >> > for a description of >> > - the cells format. >> > +- #pwm-cells: 2 for i.MX1 and 3 for i.MX27 and newer SoCs. See >> > pwm.txt >> > + in this directory for a description of the cells format. >> > - clocks : Clock specifiers for both ipg and per clocks. >> > - clock-names : Clock names should include both "ipg" and "per" >> > See the clock consumer binding, >> > @@ -17,7 +17,7 @@ See the clock consumer binding, >> > Example: >> > >> > pwm1: pwm@53fb4000 { >> > - #pwm-cells = <2>; >> > + #pwm-cells = <3>; >> > compatible = "fsl,imx53-pwm", "fsl,imx27-pwm"; >> > reg = <0x53fb4000 0x4000>; >> > clocks = <&clks IMX5_CLK_PWM1_IPG_GATE>, >> > diff --git a/drivers/pwm/pwm-imx.c b/drivers/pwm/pwm-imx.c >> > index d600fd5..c37d223 100644 >> > --- a/drivers/pwm/pwm-imx.c >> > +++ b/drivers/pwm/pwm-imx.c >> > @@ -38,6 +38,7 @@ >> > #define MX3_PWMCR_DOZEEN (1 << 24) >> > #define MX3_PWMCR_WAITEN (1 << 23) >> > #define MX3_PWMCR_DBGEN (1 << 22) >> > +#define MX3_PWMCR_POUTC (1 << 18) >> > #define MX3_PWMCR_CLKSRC_IPG_HIGH (2 << 16) >> > #define MX3_PWMCR_CLKSRC_IPG (1 << 16) >> > #define MX3_PWMCR_SWR (1 << 3) >> > @@ -180,6 +181,9 @@ static int imx_pwm_config_v2(struct pwm_chip >> > *chip, if (enable) >> > cr |= MX3_PWMCR_EN; >> > >> > + if (pwm->args.polarity == PWM_POLARITY_INVERSED) >> > + cr |= MX3_PWMCR_POUTC; >> > + >> >> This seems wrong to me, the config callback is meant for period/duty >> cycle only. > > If it is meant only for that, then the polarity should be removed from > it. > > However after very quick testing, at least on my setup, it turns out > that removing this lines causes polarity to _not_ being set (and the > polarity is not inverted). > > I will investigate this further on my setup and hopefully sent proper > patch. > >> The set_polarity callback should get called in case a >> different polarity is requested. > > On my setup the pwm2 is set from DT and pwm_backlight_probe() calls > pwm_apply_args(), so everything should work. However, as I mentioned > above there still is some problem with inversion setting. > >> >> >> > writel(cr, imx->mmio_base + MX3_PWMCR); >> > >> > return 0; >> > @@ -240,27 +244,62 @@ static void imx_pwm_disable(struct pwm_chip >> > *chip, struct pwm_device *pwm) >> > clk_disable_unprepare(imx->clk_per); >> > } >> > >> > -static struct pwm_ops imx_pwm_ops = { >> > +static int imx_pwm_set_polarity(struct pwm_chip *chip, struct >> > pwm_device *pwm, >> > + enum pwm_polarity polarity) >> > +{ >> > + struct imx_chip *imx = to_imx_chip(chip); >> > + u32 val; >> > + >> > + if (polarity == pwm->args.polarity) >> > + return 0; >> >> I don't think that this is right. Today, pwm_apply_args (in >> include/linux/pwm.h) copies the polarity from args to state.polarity, >> which is then passed as polarity argument to this function. So this >> will always return 0 afaict. > > Yes, I've overlooked it (that the state is copied). > > It can be dropped. Did you do the above test with that line dropped? > >> >> I would just drop that. >> >> There is probably one little problem in the current state of affairs: >> If the bootloader makes use of a PWM channel with inverted state, >> then the kernel would not know about that and currently assume a >> wrong initial state... I guess at one point in time we should >> implement the state retrieval callback and move to the new atomic PWM >> API, which would mean to implement apply callback. > > Are there any patches on the horizon? > Not that I know of... -- Stefan >> >> -- >> Stefan >> >> >> > + >> > + val = readl(imx->mmio_base + MX3_PWMCR); >> > + >> > + if (polarity == PWM_POLARITY_INVERSED) >> > + val |= MX3_PWMCR_POUTC; >> > + else >> > + val &= ~MX3_PWMCR_POUTC; >> > + >> > + writel(val, imx->mmio_base + MX3_PWMCR); >> > + >> > + dev_dbg(imx->chip.dev, "%s: polarity set to %s\n", >> > __func__, >> > + polarity == PWM_POLARITY_INVERSED ? "inverted" : >> > "normal"); + >> > + return 0; >> > +} >> > + >> > +static struct pwm_ops imx_pwm_ops_v1 = { >> > .enable = imx_pwm_enable, >> > .disable = imx_pwm_disable, >> > .config = imx_pwm_config, >> > .owner = THIS_MODULE, >> > }; >> > >> > +static struct pwm_ops imx_pwm_ops_v2 = { >> > + .enable = imx_pwm_enable, >> > + .disable = imx_pwm_disable, >> > + .set_polarity = imx_pwm_set_polarity, >> > + .config = imx_pwm_config, >> > + .owner = THIS_MODULE, >> > +}; >> > + >> > struct imx_pwm_data { >> > int (*config)(struct pwm_chip *chip, >> > struct pwm_device *pwm, int duty_ns, int >> > period_ns); void (*set_enable)(struct pwm_chip *chip, bool enable); >> > + struct pwm_ops *pwm_ops; >> > }; >> > >> > static struct imx_pwm_data imx_pwm_data_v1 = { >> > .config = imx_pwm_config_v1, >> > .set_enable = imx_pwm_set_enable_v1, >> > + .pwm_ops = &imx_pwm_ops_v1, >> > }; >> > >> > static struct imx_pwm_data imx_pwm_data_v2 = { >> > .config = imx_pwm_config_v2, >> > .set_enable = imx_pwm_set_enable_v2, >> > + .pwm_ops = &imx_pwm_ops_v2, >> > }; >> > >> > static const struct of_device_id imx_pwm_dt_ids[] = { >> > @@ -282,6 +321,8 @@ static int imx_pwm_probe(struct platform_device >> > *pdev) if (!of_id) >> > return -ENODEV; >> > >> > + data = of_id->data; >> > + >> > imx = devm_kzalloc(&pdev->dev, sizeof(*imx), GFP_KERNEL); >> > if (imx == NULL) >> > return -ENOMEM; >> > @@ -300,18 +341,22 @@ static int imx_pwm_probe(struct >> > platform_device *pdev) return PTR_ERR(imx->clk_ipg); >> > } >> > >> > - imx->chip.ops = &imx_pwm_ops; >> > + imx->chip.ops = data->pwm_ops; >> > imx->chip.dev = &pdev->dev; >> > imx->chip.base = -1; >> > imx->chip.npwm = 1; >> > imx->chip.can_sleep = true; >> > + if (data->pwm_ops->set_polarity) { >> > + dev_dbg(&pdev->dev, "PWM supports output >> > inversion\n"); >> > + imx->chip.of_xlate = of_pwm_xlate_with_flags; >> > + imx->chip.of_pwm_n_cells = 3; >> > + } >> > >> > r = platform_get_resource(pdev, IORESOURCE_MEM, 0); >> > imx->mmio_base = devm_ioremap_resource(&pdev->dev, r); >> > if (IS_ERR(imx->mmio_base)) >> > return PTR_ERR(imx->mmio_base); >> > >> > - data = of_id->data; >> > imx->config = data->config; >> > imx->set_enable = data->set_enable; >> > > Best regards, > > Łukasz Majewski