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Message-ID: <20140123083714.3c6e86ae@ipc1.ka-ro>
Date: Thu, 23 Jan 2014 08:37:14 +0100
From: Lothar Waßmann <LW@...O-electronics.de>
To: Sascha Hauer <s.hauer@...gutronix.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
Hi,
Sascha Hauer wrote:
> 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:
>
This wouldn't buy much without a material change to of_pwm_get().
The function of_parse_phandle_with_args() called by of_pwm_get()
requires the number of args in the pwms property be greater or equal to
the #pwm-cells property in the pwm node. Thus, the interesting case of
having #pwm-cells = <3> without changing the existing users is
prohibited by of_parse_phandle_with_args().
of_pwm_get() would have to be changed to something like below to allow
this:
struct pwm_device *of_pwm_get(struct device_node *np, const char *con_id)
{
struct pwm_device *pwm = NULL;
struct of_phandle_args args;
struct pwm_chip *pc;
int index = 0;
int err;
struct property *prop;
u32 num_cells;
int i;
const __be32 *list;
if (con_id) {
index = of_property_match_string(np, "pwm-names", con_id);
if (index < 0)
return ERR_PTR(index);
}
args.np = of_parse_phandle(np, "pwms", index);
if (!args.np) {
pr_err("%s(): property 'pwms' not found in '%s'\n",
__func__, np->full_name);
return ERR_PTR(-ENOENT);
}
err = of_property_read_u32(args.np, "#pwm-cells", &num_cells);
if (err) {
pr_err("%s(): could not read property '#pwm-cells' in '%s': %d\n",
__func__, args.np->full_name, err);
return ERR_PTR(err);
}
prop = of_find_property(np, "pwms", NULL);
if (WARN_ON(!prop))
return ERR_PTR(-EINVAL);
args.args_count = prop->length / sizeof(u32) - 1;
list = prop->value;
for (i = 0; i < args.args_count; i++)
args.args[i] = be32_to_cpup(++list);
pc = of_node_to_pwmchip(args.np);
if (IS_ERR(pc)) {
pr_err("%s(): PWM chip not found\n", __func__);
pwm = ERR_CAST(pc);
goto put;
}
[...]
Lothar Waßmann
--
___________________________________________________________
Ka-Ro electronics GmbH | Pascalstraße 22 | D - 52076 Aachen
Phone: +49 2408 1402-0 | Fax: +49 2408 1402-10
Geschäftsführer: Matthias Kaussen
Handelsregistereintrag: Amtsgericht Aachen, HRB 4996
www.karo-electronics.de | info@...o-electronics.de
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