Re: [PATCH 2/2] pwm: vt8500: Add support for .set_polarity

From: Thierry Reding
Date: Wed Jan 02 2013 - 09:09:36 EST


On Mon, Dec 31, 2012 at 09:23:25AM +1300, Tony Prisk wrote:
> Add support to set polarity on pwm devices, allowing for inverted
> duty cycles.

"PWM devices", please. Maybe the subject could be something less API
specific, like "pwm: vt8500: Add polarity support".

> .../devicetree/bindings/pwm/vt8500-pwm.txt | 7 ++++---
> drivers/pwm/pwm-vt8500.c | 21 ++++++++++++++++++++
> 2 files changed, 25 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/pwm/vt8500-pwm.txt b/Documentation/devicetree/bindings/pwm/vt8500-pwm.txt
> index bcc6367..f71cc8d 100644
> --- a/Documentation/devicetree/bindings/pwm/vt8500-pwm.txt
> +++ b/Documentation/devicetree/bindings/pwm/vt8500-pwm.txt
> @@ -3,14 +3,15 @@ VIA/Wondermedia VT8500/WM8xxx series SoC PWM controller
> Required properties:
> - compatible: should be "via,vt8500-pwm"
> - reg: physical base address and length of the controller's registers
> -- #pwm-cells: should be 2. The first cell specifies the per-chip index
> - of the PWM to use and the second cell is the period in nanoseconds.
> +- #pwm-cells: should be 3. The first cell specifies the per-chip index
> + of the PWM to use, the second cell is the period in nanoseconds, and the
> + third cell is for flags.

This needs to document what flags the third cell encodes and how. Either
that or refer to the generic PWM binding documentation.

> diff --git a/drivers/pwm/pwm-vt8500.c b/drivers/pwm/pwm-vt8500.c
> index 27ed0f4..9abf561 100644
> --- a/drivers/pwm/pwm-vt8500.c
> +++ b/drivers/pwm/pwm-vt8500.c
> @@ -164,10 +164,31 @@ static void vt8500_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
> clk_disable(vt8500->clk);
> }
>
> +static int vt8500_pwm_set_polarity(struct pwm_chip *chip,
> + struct pwm_device *pwm,
> + enum pwm_polarity polarity)
> +{
> + struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
> + u32 val;
> +
> + val = readl(vt8500->base + REG_CTRL(pwm->hwpwm));
> +
> + if (polarity == PWM_POLARITY_INVERSED)
> + val |= CTRL_INVERT;
> + else
> + val &= ~CTRL_INVERT;
> +
> + writel(val, vt8500->base + REG_CTRL(pwm->hwpwm));
> + pwm_busy_wait(vt8500, pwm->hwpwm, STATUS_CTRL_UPDATE);
> +
> + return 0;
> +}
> +
> static struct pwm_ops vt8500_pwm_ops = {
> .enable = vt8500_pwm_enable,
> .disable = vt8500_pwm_disable,
> .config = vt8500_pwm_config,
> + .set_polarity = vt8500_pwm_set_polarity,
> .owner = THIS_MODULE,
> };

This patch is missing the corresponding changes to the DT code. You need
to override the pwm_chip's .of_xlate() and .of_pwm_n_cells fields. You
can look at the TI EHRPWM driver if you need inspiration.

Thierry

Attachment: pgp00000.pgp
Description: PGP signature