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Message-ID: <20140116160356.GY16215@pengutronix.de>
Date: Thu, 16 Jan 2014 17:03:57 +0100
From: Sascha Hauer <s.hauer@...gutronix.de>
To: Lothar Waßmann <LW@...O-electronics.de>
Cc: linux-arm-kernel@...ts.infradead.org,
Shawn Guo <shawn.guo@...aro.org>,
Sascha Hauer <kernel@...gutronix.de>,
Thierry Reding <thierry.reding@...il.com>,
Rob Herring <robh+dt@...nel.org>,
Pawel Moll <pawel.moll@....com>,
Mark Rutland <mark.rutland@....com>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
Kumar Gala <galak@...eaurora.org>,
Rob Landley <rob@...dley.net>, linux-pwm@...r.kernel.org,
devicetree@...r.kernel.org, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 2/2] pwm: imx: support polarity inversion
On Thu, Jan 16, 2014 at 09:06:25AM +0100, Lothar Waßmann wrote:
> The i.MX PWM controller supports inverting the polarity of the PWM
> output. Make this feature available in the pxm-imx driver.
>
> Signed-off-by: Lothar Waßmann <LW@...O-electronics.de>
> ---
> Documentation/devicetree/bindings/pwm/imx-pwm.txt | 5 +-
> drivers/pwm/pwm-imx.c | 42 +++++++++++++++++++++
> 2 files changed, 45 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/pwm/imx-pwm.txt b/Documentation/devicetree/bindings/pwm/imx-pwm.txt
> index b50d7a6d..d0b04b5 100644
> --- a/Documentation/devicetree/bindings/pwm/imx-pwm.txt
> +++ b/Documentation/devicetree/bindings/pwm/imx-pwm.txt
> @@ -3,8 +3,9 @@ Freescale i.MX PWM controller
> Required properties:
> - compatible: should be "fsl,<soc>-pwm"
> - 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: may be 2 for backwards compatibility or 3 to support
> + switching the output polarity. See pwm.txt in this directory for a
> + description of the cells format.
> - interrupts: The interrupt for the pwm controller
>
> Example:
> diff --git a/drivers/pwm/pwm-imx.c b/drivers/pwm/pwm-imx.c
> index 3b00a82..05461bb 100644
> --- a/drivers/pwm/pwm-imx.c
> +++ b/drivers/pwm/pwm-imx.c
> @@ -36,6 +36,7 @@
> #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_EN (1 << 0)
> @@ -138,6 +139,9 @@ static int imx_pwm_config_v2(struct pwm_chip *chip,
> if (test_bit(PWMF_ENABLED, &pwm->flags))
> cr |= MX3_PWMCR_EN;
>
> + if (pwm->polarity == PWM_POLARITY_INVERSED)
> + cr |= MX3_PWMCR_POUTC;
> +
> writel(cr, imx->mmio_base + MX3_PWMCR);
>
> return 0;
> @@ -155,6 +159,11 @@ static void imx_pwm_set_enable_v2(struct pwm_chip *chip, bool enable)
> else
> val &= ~MX3_PWMCR_EN;
>
> + if (chip->pwms[0].polarity == PWM_POLARITY_INVERSED)
> + val |= MX3_PWMCR_POUTC;
> + else
> + val &= ~MX3_PWMCR_POUTC;
> +
> writel(val, imx->mmio_base + MX3_PWMCR);
> }
>
> @@ -198,6 +207,17 @@ static void imx_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
> clk_disable_unprepare(imx->clk_per);
> }
>
> +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);
> +
> + 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 = {
> .enable = imx_pwm_enable,
> .disable = imx_pwm_disable,
> @@ -209,6 +229,7 @@ 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);
> + unsigned output_polarity:1;
> };
>
> static struct imx_pwm_data imx_pwm_data_v1 = {
> @@ -219,6 +240,7 @@ static struct imx_pwm_data imx_pwm_data_v1 = {
> static struct imx_pwm_data imx_pwm_data_v2 = {
> .config = imx_pwm_config_v2,
> .set_enable = imx_pwm_set_enable_v2,
> + .output_polarity = 1,
> };
>
> static const struct of_device_id imx_pwm_dt_ids[] = {
> @@ -271,6 +293,26 @@ static int imx_pwm_probe(struct platform_device *pdev)
> return PTR_ERR(imx->mmio_base);
>
> data = of_id->data;
> + if (data->output_polarity) {
> + const struct device_node *np = pdev->dev.of_node;
> + u32 num_cells;
> +
> + dev_dbg(&pdev->dev, "PWM supports output inversion\n");
> + ret = of_property_read_u32(np, "#pwm-cells", &num_cells);
> + if (ret < 0) {
> + dev_err(&pdev->dev, "missing property '#pwm-cells'\n");
> + return ret;
> + }
> + if (num_cells == 3) {
> + imx_pwm_ops.set_polarity = imx_pwm_set_polarity;
> + imx->chip.of_xlate = of_pwm_xlate_with_flags;
> + } else if (num_cells != 2) {
> + dev_err(&pdev->dev, "'#pwm-cells' must be <2> or <3>\n");
> + return -EINVAL;
> + }
> + imx->chip.of_pwm_n_cells = num_cells;
> + }
Can't this be done in the PWM core? Right now the PWM core checks for
of_pwm_n_cells before calling ->of_xlate. IMO this check should be done
in the of_xlate hook. Then of_pwm_simple_xlate and
of_pwm_xlate_with_flags can be merged into something like:
static struct pwm_device *
of_pwm_simple_xlate(struct pwm_chip *pc, const struct of_phandle_args
*args)
{
struct pwm_device *pwm;
int ret;
if (pc->of_pwm_n_cells < 2)
return ERR_PTR(-EINVAL);
if (args->args[0] >= pc->npwm)
return ERR_PTR(-EINVAL);
pwm = pwm_request_from_chip(pc, args->args[0], NULL);
if (IS_ERR(pwm))
return pwm;
if (pc->of_pwm_n_cells >= 3) {
if (args->args[2] & PWM_POLARITY_INVERTED)
ret = pwm_set_polarity(pwm, PWM_POLARITY_INVERSED);
else
ret = pwm_set_polarity(pwm, PWM_POLARITY_NORMAL);
if (ret)
return ret;
}
pwm_set_period(pwm, args->args[1]);
return pwm;
}
Sascha
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