[PATCH 08/15] pwm: Add new pwm-samsung driver

Tue Jun 18 15:41:09 EDT 2013

On Monday 17 of June 2013 22:29:11 Thierry Reding wrote:
> On Wed, Jun 05, 2013 at 11:18:13PM +0200, Tomasz Figa wrote:
> > This patch introduces new Samsung PWM driver, which uses Samsung
> > PWM/timer master driver to control shared parts of the hardware.
> > 
> > Signed-off-by: Tomasz Figa <tomasz.figa at gmail.com>
> 
> Sorry for jumping in so late, I've been busy with other things lately.
> 
> > ---
> > 
> >  drivers/pwm/Makefile      |   1 +
> >  drivers/pwm/pwm-samsung.c | 528
> >  ++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 529
> >  insertions(+)
> >  create mode 100644 drivers/pwm/pwm-samsung.c
> > 
> > diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> > index 229a599..833c3ac 100644
> > --- a/drivers/pwm/Makefile
> > +++ b/drivers/pwm/Makefile
> > @@ -9,6 +9,7 @@ obj-$(CONFIG_PWM_MXS)		+= pwm-mxs.o
> > 
> >  obj-$(CONFIG_PWM_PUV3)		+= pwm-puv3.o
> >  obj-$(CONFIG_PWM_PXA)		+= pwm-pxa.o
> >  obj-$(CONFIG_PWM_SAMSUNG)	+= pwm-samsung-legacy.o
> > 
> > +obj-$(CONFIG_PWM_SAMSUNG)	+= pwm-samsung.o
> > 
> >  obj-$(CONFIG_PWM_SPEAR)		+= pwm-spear.o
> >  obj-$(CONFIG_PWM_TEGRA)		+= pwm-tegra.o
> >  obj-$(CONFIG_PWM_TIECAP)	+= pwm-tiecap.o
> > 
> > diff --git a/drivers/pwm/pwm-samsung.c b/drivers/pwm/pwm-samsung.c
> > new file mode 100644
> > index 0000000..61bed3d
> > --- /dev/null
> > +++ b/drivers/pwm/pwm-samsung.c
> > @@ -0,0 +1,528 @@
> > +/* drivers/pwm/pwm-samsung.c
> 
> Nit: this line can be dropped. It serves no purpose.
> 
> > + *
> > + * Copyright (c) 2007 Ben Dooks
> > + * Copyright (c) 2008 Simtec Electronics
> > + *     Ben Dooks <ben at simtec.co.uk>, <ben-linux at fluff.org>
> > + * Copyright (c) 2013 Tomasz Figa <tomasz.figa at gmail.com>
> > + *
> > + * PWM driver for Samsung SoCs
> > + *
> > + * This program is free software; you can redistribute it and/or
> > modify + * it under the terms of the GNU General Public License as
> > published by + * the Free Software Foundation; either version 2 of
> > the License. +*/
> 
> Nit: the */ should align with the * above.
> 
> > +struct samsung_pwm_channel {
> > +	unsigned long period_ns;
> > +	unsigned long duty_ns;
> > +	unsigned long tin_ns;
> > +};
> > +
> > +struct samsung_pwm_chip {
> > +	struct pwm_chip chip;
> > +	struct samsung_pwm_variant variant;
> > +	struct samsung_pwm_channel channels[SAMSUNG_PWM_NUM];
> 
> The new driver for Renesas did something similar, but I want to
> discourage storing per-channel data within the chip structure.
> 
> The PWM framework provides a way to store this information along with
> the PWM device (see pwm_{set,get}_chip_data()).

OK, this looks good, but in my case is not really useful. I need to access 
those channel data in my suspend/resume callbacks and obviously I don't 
have access to any pwm_device there. Any suggestions?

Best regards,
Tomasz

> > +
> > +	void __iomem *base;
> > +	struct clk *base_clk;
> > +	struct clk *tclk0;
> > +	struct clk *tclk1;
> > +};
> > +#define to_samsung_pwm_chip(chip)	\
> > +			container_of(chip, struct samsung_pwm_chip, chip)
> 
> Can you turn this into a static inline function please?
> 
> > +#ifndef CONFIG_CLKSRC_SAMSUNG_PWM
> > +static DEFINE_SPINLOCK(samsung_pwm_lock);
> > +#endif
> 
> Why is this lock global? Shouldn't it more correctly be part of
> samsung_pwm_chip?
> 
> > +static void pwm_samsung_set_divisor(struct samsung_pwm_chip *pwm,
> > +					unsigned int channel, u8 divisor)
> 
> Nit: please align arguments on subsequent lines with the first argument
> of the first line. There's many more of these but I haven't mentioned
> them all explicitly.
> 
> > +static inline int pwm_samsung_is_tdiv(struct samsung_pwm_chip *chip,
> 
> Any particular reason for making this inline?
> 
> > +static int pwm_samsung_config(struct pwm_chip *chip, struct
> > pwm_device *pwm, +		int duty_ns, int period_ns)
> > +{
> > +	struct samsung_pwm_chip *our_chip = to_samsung_pwm_chip(chip);
> > +	struct samsung_pwm_channel *chan = &our_chip->channels[pwm-
>hwpwm];
> > +	unsigned long tin_ns = chan->tin_ns;
> > +	unsigned int tcon_chan = pwm->hwpwm;
> > +	unsigned long tin_rate;
> > +	unsigned long period;
> > +	unsigned long flags;
> > +	unsigned long tcnt;
> 
> Many of these unsigned long variable could be declared on a single line
> to make the function shorter.
> 
> > +	long tcmp;
> > +	u32 tcon;
> > +
> > +	/* We currently avoid using 64bit arithmetic by using the
> > +	 * fact that anything faster than 1Hz is easily representable
> > +	 * by 32bits. */
> 
> Can you turn these into proper block-style comments? Like so:
> 
> 	/*
> 	 * We currently...
> 	 * ...
> 	 * by 32 bits.
> 	 */
> 
> > +	if (period_ns > NSEC_PER_SEC || duty_ns > NSEC_PER_SEC)
> > +		return -ERANGE;
> 
> Note that technically you only need to check period_ns because the core
> already ensures that duty_ns <= period_ns.
> 
> > +static int pwm_samsung_set_polarity(struct pwm_chip *chip,
> > +			struct pwm_device *pwm, enum pwm_polarity 
polarity)
> > +{
> > +	struct samsung_pwm_chip *our_chip = to_samsung_pwm_chip(chip);
> > +	unsigned int channel = pwm->hwpwm;
> > +	unsigned long flags;
> > +	u32 tcon;
> > +
> > +	if (channel > 0)
> > +		++channel;
> 
> You have to repeat that in quite a few places, so I wonder if it'd make
> sense to wrap it into a function and add a comment about why the
> increment is necessary.
> 
> > +static struct pwm_ops pwm_samsung_ops = {
> 
> "static const" please.
> 
> > +#ifdef CONFIG_OF
> > +static const struct samsung_pwm_variant s3c24xx_variant = {
> > +	.bits		= 16,
> > +	.div_base	= 1,
> > +	.has_tint_cstat	= false,
> > +	.tclk_mask	= (1 << 4),
> > +};
> > +
> > +static const struct samsung_pwm_variant s3c64xx_variant = {
> > +	.bits		= 32,
> > +	.div_base	= 0,
> > +	.has_tint_cstat	= true,
> > +	.tclk_mask	= (1 << 7) | (1 << 6) | (1 << 5),
> > +};
> > +
> > +static const struct samsung_pwm_variant s5p64x0_variant = {
> > +	.bits		= 32,
> > +	.div_base	= 0,
> > +	.has_tint_cstat	= true,
> > +	.tclk_mask	= 0,
> > +};
> > +
> > +static const struct samsung_pwm_variant s5p_variant = {
> > +	.bits		= 32,
> > +	.div_base	= 0,
> > +	.has_tint_cstat	= true,
> > +	.tclk_mask	= (1 << 5),
> > +};
> > +
> > +static const struct of_device_id samsung_pwm_matches[] = {
> > +	{ .compatible = "samsung,s3c2410-pwm", .data = &s3c24xx_variant },
> > +	{ .compatible = "samsung,s3c6400-pwm", .data = &s3c64xx_variant },
> > +	{ .compatible = "samsung,s5p6440-pwm", .data = &s5p64x0_variant },
> > +	{ .compatible = "samsung,s5pc100-pwm", .data = &s5p_variant },
> > +	{ .compatible = "samsung,exynos4210-pwm", .data = &s5p64x0_variant
> > },
> > +	{},
> > +};
> > +#endif
> > +
> > +static int pwm_samsung_parse_dt(struct samsung_pwm_chip *chip)
> > +{
> > +	struct device_node *np = chip->chip.dev->of_node;
> > +	const struct of_device_id *match;
> > +	struct property *prop;
> > +	const __be32 *cur;
> > +	u32 val;
> > +
> > +	match = of_match_node(samsung_pwm_matches, np);
> > +	if (!match)
> > +		return -ENODEV;
> > +
> > +	memcpy(&chip->variant, match->data, sizeof(chip->variant));
> > +
> > +	of_property_for_each_u32(np, "samsung,pwm-outputs", prop, cur, 
val)
> > {
> > +		if (val >= SAMSUNG_PWM_NUM) {
> > +			pr_warning("%s: invalid channel index in 
samsung,pwm-outputs
> > property\n", +								
__func__);
> > +			continue;
> > +		}
> > +		chip->variant.output_mask |= 1 << val;
> 
> Could the output_mask be moved to the struct samsung_pwm_chip instead?
> The reason I ask is because it would allow you to make the variant
> constant throughout the driver.
> 
> > +static int pwm_samsung_probe(struct platform_device *pdev)
> > +{
> > +	struct device *dev = &pdev->dev;
> > +	struct samsung_pwm_chip *chip;
> > +	struct resource *res;
> > +	int ret;
> > +
> > +	chip = devm_kzalloc(&pdev->dev, sizeof(*chip), GFP_KERNEL);
> > +	if (chip == NULL) {
> > +		dev_err(dev, "failed to allocate driver data\n");
> > +		return -ENOMEM;
> > +	}
> > +
> > +	chip->chip.dev = &pdev->dev;
> > +	chip->chip.ops = &pwm_samsung_ops;
> > +	chip->chip.base = -1;
> > +	chip->chip.npwm = SAMSUNG_PWM_NUM;
> > +
> > +	if (pdev->dev.of_node) {
> 
> Maybe add an IS_ENABLED(CONFIG_OF) check here? That'd allow all OF-
> related code to be thrown away if OF isn't selected.
> 
> > +		ret = pwm_samsung_parse_dt(chip);
> > +		if (ret)
> > +			return ret;
> > +
> > +		chip->chip.of_xlate = of_pwm_xlate_with_flags;
> > +		chip->chip.of_pwm_n_cells = 3;
> > +	} else {
> > +		if (!pdev->dev.platform_data) {
> > +			dev_err(&pdev->dev, "no platform data 
specified\n");
> > +			return -EINVAL;
> > +		}
> > +
> > +		memcpy(&chip->variant, pdev->dev.platform_data,
> > +							sizeof(chip-
>variant));
> > +	}
> 
> Obviously this needs some modification in order for the variant to
> become constant. But I think you can easily do so by making the driver
> match using the platform_driver's id_table field, similar to how the
> matching is done for OF.
> 
> > +	chip->base = devm_request_and_ioremap(&pdev->dev, res);
> > +	if (!chip->base) {
> > +		dev_err(&pdev->dev, "failed to request and map 
registers\n");
> > +		return -ENOMEM;
> > +	}
> 
> devm_request_and_ioremap() is now deprecated and in the process of being
> removed. You should use devm_ioremap_resource() instead.
> 
> > +
> > +	chip->base_clk = devm_clk_get(&pdev->dev, "timers");
> > +	if (IS_ERR(chip->base_clk)) {
> > +		dev_err(dev, "failed to get timer base clk\n");
> > +		return PTR_ERR(chip->base_clk);
> > +	}
> > +	clk_prepare_enable(chip->base_clk);
> 
> You need to check the return value of clk_prepare_enable(). And if I was
> very pedantic, there should be a blank line before this one.
> 
> > +	ret = pwmchip_add(&chip->chip);
> > +	if (ret < 0) {
> > +		dev_err(dev, "failed to register pwm\n");
> 
> "failed to register PWM chip" please.
> 
> > +		goto err_clk_disable;
> > +	}
> > +
> > +	dev_info(dev, "base_clk at %lu, tclk0 at %lu, tclk1 at %lu\n",
> > +		clk_get_rate(chip->base_clk),
> > +		!IS_ERR(chip->tclk0) ? clk_get_rate(chip->tclk0) : 0,
> > +		!IS_ERR(chip->tclk1) ? clk_get_rate(chip->tclk1) : 0);
> > +
> > +	platform_set_drvdata(pdev, chip);
> > +
> > +	return 0;
> > +
> > +err_clk_disable:
> > +	clk_disable_unprepare(chip->base_clk);
> > +
> > +	return ret;
> 
> There's only a single case where this can actually happen, so I don't
> think you need the label here. Just put the clk_disable_unprepare() call
> and the return statement where you jump to the label.
> 
> > +#ifdef CONFIG_PM
> 
> I think this should really be CONFIG_PM_SLEEP.
> 
> > +static struct dev_pm_ops pwm_samsung_pm_ops = {
> 
> "static const" please.
> 
> Thierry