linux-kernel - Re: [RESEND PATCH v2 1/4] pwm: Add support for Meson PWM Controller

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Date:   Mon, 22 Aug 2016 14:16:52 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     thierry.reding@...il.com, carlo@...one.org, khilman@...libre.com
Cc:     linux-pwm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH v2 1/4] pwm: Add support for Meson PWM Controller

Hi Thierry,

On 08/20/2016 08:34 PM, Neil Armstrong wrote:
> Add support for the PWM controller found in the Amlogic SoCs.
> This driver supports the Meson8b and GXBB SoCs.
> 
> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
> ---
>  drivers/pwm/Kconfig     |   9 +
>  drivers/pwm/Makefile    |   1 +
>  drivers/pwm/pwm-meson.c | 491 ++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 501 insertions(+)
>  create mode 100644 drivers/pwm/pwm-meson.c
> 

[...]

> diff --git a/drivers/pwm/pwm-meson.c b/drivers/pwm/pwm-meson.c
> new file mode 100644
> index 0000000..9e7ecf5
> --- /dev/null
> +++ b/drivers/pwm/pwm-meson.c

[...]

> +
> +static const char * const pwm_parents[] = {
> +	"xtal", "vid_pll", "fclk_div4", "fclk_div3", NULL
> +};

Aww, crap, it's "vid_pll" on meson8b and "hdmi_pll" for gxbb.
I'll add it to DT mach data.

> +static int meson_pwm_enable(struct pwm_chip *chip,
> +				 struct pwm_device *pwm)
> +{
> +	struct meson_pwm_chip *pwm_data = to_meson_pwm_chip(chip);
> +	unsigned int id = pwm->hwpwm;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&pwm_data->lock, flags);
> +	switch (id) {
> +	case PWM_A:
> +		writel(readl(pwm_data->base + REG_MISC_AB) | MISC_A_EN,
> +			pwm_data->base + REG_MISC_AB);

Found an issue here, the HW requires to re-write the clock counts register even if the value is correct.
Let's got for a v3 !

> +		break;
> +
> +	case PWM_B:
> +		writel(readl(pwm_data->base + REG_MISC_AB) | MISC_B_EN,
> +			pwm_data->base + REG_MISC_AB);
> +		break;
> +
> +	default:
> +		break;
> +	}
> +	spin_unlock_irqrestore(&pwm_data->lock, flags);
> +
> +	return 0;
> +}

Is it worth rewriting the driver using the apply callback ?
I'll wish to have it for 4.9 if possible, do you think it's possible ?

Neil