On Mon, Nov 18, 2013 at 10:54:58AM -0800, Tim Kryger wrote:
[...]
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
[...]
> +config PWM_BCM_KONA
> + tristate "Kona PWM support"
> + depends on ARCH_BCM_MOBILE
> + default y
Why do you want this to be the default? Shouldn't this be something that
a default configuration selects explicitly?
> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
[...]
> obj-$(CONFIG_PWM_BFIN) += pwm-bfin.o
> +obj-$(CONFIG_PWM_BCM_KONA) += pwm-bcm-kona.o
'C' < 'F'
> diff --git a/drivers/pwm/pwm-bcm-kona.c b/drivers/pwm/pwm-bcm-kona.c
[...]
> +#include <linux/clk.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/ioport.h>
> +#include <linux/math64.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/pwm.h>
> +#include <linux/slab.h>
> +#include <linux/types.h>
> +
> +#define KONA_PWM_CHANNEL_CNT 6
You use this exactly once, so there's no need for this define.
> +#define PWM_CONTROL_OFFSET (0x00000000)
I'd prefer if you dropped the _OFFSET suffix here.
> +#define PWM_CONTROL_INITIAL (0x3f3f3f00)
Can this not be expressed as a bitmask of values for the individual
fields.
> +#define PWMOUT_POLARITY(chan) (0x1 << (8 + chan))
This seems to only account for bits 8-13, what about the others?
> +#define PWMOUT_ENABLE(chan) (0x1 << chan)
Well, this accounts for bits 0-5, that still leaves 16-21 and 24-29.
Also perhaps PWMOUT_POLARITY and PWMOUT_ENABLE should be defined as
PWM_CONTROL_POLARITY and PWM_CONTROL_ENABLE. That makes it easy to see
which register they are related to.
> +#define PRESCALE_OFFSET (0x00000004)
> +#define PRESCALE_SHIFT(chan) (chan << 2)
I'm confused. This allocates 2 bits for each channel...
> +#define PRESCALE_MASK(chan) (~(0x7 << (chan << 2)))
> +#define PRESCALE_MIN (0x00000000)
> +#define PRESCALE_MAX (0x00000007)
... but 0x7 requires at least 3 bits.
> +#define PERIOD_COUNT_OFFSET(chan) (0x00000008 + (chan << 3))
> +#define PERIOD_COUNT_MIN (0x00000002)
> +#define PERIOD_COUNT_MAX (0x00ffffff)
Why PERIOD_COUNT? PERIOD is descriptive enough. Or is this the name as
found in the manual?
> +#define DUTY_CYCLE_HIGH_OFFSET(chan) (0x0000000c + (chan << 3))
> +#define DUTY_CYCLE_HIGH_MIN (0x00000000)
> +#define DUTY_CYCLE_HIGH_MAX (0x00ffffff)
By definition the duty-cycle is where the signal is high. Again, if this
is how the manual names the registers it's fine.
> +struct kona_pwmc {
> + struct pwm_chip chip;
> + void __iomem *base;
> + struct clk *clk;
> +};
> +
> +static void kona_pwmc_apply_settings(struct kona_pwmc *kp, int chan)
unsigned int for "chan"?
> +{
> + /* New settings take effect on rising edge of enable bit */
> + writel(readl(kp->base + PWM_CONTROL_OFFSET) & ~PWMOUT_ENABLE(chan),
> + kp->base + PWM_CONTROL_OFFSET);
> + writel(readl(kp->base + PWM_CONTROL_OFFSET) | PWMOUT_ENABLE(chan),
> + kp->base + PWM_CONTROL_OFFSET);
That's too cluttered for my taste. Please make this more explicit:
value = readl(...);
value &= ~...;
writel(value, ...);
value = readl(...);
value |= ...;
writel(value, ...);
> +}
> +
> +static int kona_pwmc_config(struct pwm_chip *chip, struct pwm_device *pwm,
> + int duty_ns, int period_ns)
> +{
> + struct kona_pwmc *kp = dev_get_drvdata(chip->dev);
> + u64 val, div, clk_rate;
> + unsigned long prescale = PRESCALE_MIN, pc, dc;
> + int chan = pwm->hwpwm;
pwm->hwpwm is unsigned, so chan should be as well.
> +
> + /*
> + * Find period count, duty count and prescale to suit duty_ns and
> + * period_ns. This is done according to formulas described below:
> + *
> + * period_ns = 10^9 * (PRESCALE + 1) * PC / PWM_CLK_RATE
> + * duty_ns = 10^9 * (PRESCALE + 1) * DC / PWM_CLK_RATE
> + *
> + * PC = (PWM_CLK_RATE * period_ns) / (10^9 * (PRESCALE + 1))
> + * DC = (PWM_CLK_RATE * duty_ns) / (10^9 * (PRESCALE + 1))
> + */
> +
> + clk_rate = clk_get_rate(kp->clk);
> + while (1) {
Newline between the above two lines please.
> + div = 1000000000;
> + div *= 1 + prescale;
> + val = clk_rate * period_ns;
> + pc = div64_u64(val, div);
> + val = clk_rate * duty_ns;
> + dc = div64_u64(val, div);
> +
> + /* If duty_ns or period_ns are not achievable then return */
> + if (pc < PERIOD_COUNT_MIN || dc < DUTY_CYCLE_HIGH_MIN)
> + return -EINVAL;
> +
> + /*
> + * If pc or dc have crossed their upper limit, then increase
> + * prescale and recalculate pc and dc.
> + */
> + if (pc > PERIOD_COUNT_MAX || dc > DUTY_CYCLE_HIGH_MAX) {
> + if (++prescale > PRESCALE_MAX)
> + return -EINVAL;
> + continue;
> + }
This looks unintuitive to me, perhaps:
if (pc <= PERIOD_COUNT_MAX && dc <= DUTY_CYCLE_HIGH_MAX)
break;
if (++prescale > PRESCALE_MAX)
return -EINVAL;
?
> + /* Program prescale */
> + writel((readl(kp->base + PRESCALE_OFFSET) & PRESCALE_MASK(chan)) |
> + prescale << PRESCALE_SHIFT(chan),
> + kp->base + PRESCALE_OFFSET);
Again, please split this into separate read/modify/write steps.
> +
> + /* Program period count */
> + writel(pc, kp->base + PERIOD_COUNT_OFFSET(chan));
> +
> + /* Program duty cycle high count */
> + writel(dc, kp->base + DUTY_CYCLE_HIGH_OFFSET(chan));
I don't think we need the comments. The register names are fairly
descriptive, so the comments add no value.
> +
> + if (test_bit(PWMF_ENABLED, &pwm->flags))
> + kona_pwmc_apply_settings(kp, chan);
> +
> + return 0;
> +}
> +
> +static int kona_pwmc_enable(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> + return kona_pwmc_config(chip, pwm, pwm->duty_cycle, pwm->period);
> +}
Why can't this just enable the channel? Why go through all the trouble
of running the whole computations again?
> +
> +static void kona_pwmc_disable(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> + struct kona_pwmc *kp = dev_get_drvdata(chip->dev);
> + int chan = pwm->hwpwm;
> +
> + /*
> + * The PWM hardware lacks a proper way to be disabled so
> + * we just program zero duty cycle high count instead
> + */
So clearing the enable bit doesn't disable the PWM channel?
> +
> + writel(0, kp->base + DUTY_CYCLE_HIGH_OFFSET(chan));
> + kona_pwmc_apply_settings(kp, chan);
> +}
> +
> +static const struct pwm_ops kona_pwm_ops = {
> + .config = kona_pwmc_config,
> + .owner = THIS_MODULE,
> + .enable = kona_pwmc_enable,
> + .disable = kona_pwmc_disable,
> +};
Please move the .owner field to be the last field. Also you did define
the PWMOUT_POLARITY field, which indicates that the hardware supports
changing the signal's polarity, yet you don't implement the polarity
feature. Why not?
> +static int kona_pwmc_probe(struct platform_device *pdev)
> +{
> + struct kona_pwmc *kp;
> + struct resource *res;
> + int ret = 0;
I don't think this needs to be initialized.
> +
> + dev_dbg(&pdev->dev, "bcm_kona_pwmc probe\n");
Can this be removed?
> +
> + kp = devm_kzalloc(&pdev->dev, sizeof(*kp), GFP_KERNEL);
> + if (kp == NULL)
> + return -ENOMEM;
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + kp->base = devm_ioremap_resource(&pdev->dev, res);
> + if (IS_ERR(kp->base))
> + return PTR_ERR(kp->base);
> +
> + kp->clk = devm_clk_get(&pdev->dev, NULL);
> + if (IS_ERR(kp->clk)) {
> + dev_err(&pdev->dev, "Clock get failed : Err %d\n", ret);
ret would be 0 here, indicating no error. This should probably be
PTR_ERR(kp->clk). Also please make the error message more consistent,
this one and the one below use completely different styles. Also, "Err"
isn't very useful in an error message. Something like:
dev_err(&pdev->dev, "failed to get clock: %d\n",
PTR_ERR(kp->clk));
would be good.
> + return PTR_ERR(kp->clk);
> + }
> +
> + ret = clk_prepare_enable(kp->clk);
> + if (ret < 0)
> + return ret;
Do you really want the clock enabled all the time? Why not just
clk_enable() whenever a PWM is enabled? If you need the clock for
register access, you can also bracket register accesses with
clk_enable() and clk_disable(). Perhaps the power savings aren't worth
the added effort, so if you'd rather not do that, I'm fine with it, too.
> +
> + /* Set smooth mode, push/pull, and normal polarity for all channels */
> + writel(PWM_CONTROL_INITIAL, kp->base + PWM_CONTROL_OFFSET);
I'd expect to see bitfield definitions for smooth mode and push/pull,
and PWM_CONTROL_INITIAL to be defined in terms of those. Better yet
would be to have a value constructed at runtime with the initial value.
> + dev_set_drvdata(&pdev->dev, kp);
platform_set_drvdata(), please.
> + kp->chip.dev = &pdev->dev;
> + kp->chip.ops = &kona_pwm_ops;
> + kp->chip.base = -1;
> + kp->chip.npwm = KONA_PWM_CHANNEL_CNT;
> +
> + ret = pwmchip_add(&kp->chip);
> + if (ret < 0) {
> + clk_disable_unprepare(kp->clk);
> + dev_err(&pdev->dev, "pwmchip_add() failed: Err %d\n", ret);
For consistency with my above recommendation:
dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret);
Also, I'd move the error message before clk_disable_unprepare(). There's
no technical reason really, but it's far more common that way around.
> + }
> +
> + return ret;
> +}
> +
> +static int kona_pwmc_remove(struct platform_device *pdev)
> +{
> + struct kona_pwmc *kp = platform_get_drvdata(pdev);
> +
> + clk_disable_unprepare(kp->clk);
> + return pwmchip_remove(&kp->chip);
> +}
> +
> +static const struct of_device_id bcm_kona_pwmc_dt[] = {
> + {.compatible = "brcm,kona-pwm"},
Needs spaces after { and before }.
> + {},
Should be: { }.
> +};
> +MODULE_DEVICE_TABLE(of, bcm_kona_pwmc_dt);
> +
> +static struct platform_driver kona_pwmc_driver = {
> +
> + .driver = {
> + .name = "bcm-kona-pwm",
> + .owner = THIS_MODULE,
> + .of_match_table = bcm_kona_pwmc_dt,
> + },
The alignment is weird, should be:
.driver = {
.name = "bcm-kona-pwm",
.owner = THIS_MODULE,
.of_match_table = bcm_kona_pwmc_dt,
},
You can also leave out the .owner field, that's assigned automatically
by the driver core.
> +
> + .probe = kona_pwmc_probe,
No blank line before this one.
> + .remove = kona_pwmc_remove,
> +};
> +
> +module_platform_driver(kona_pwmc_driver);
No blank line before this one.
> +
> +MODULE_AUTHOR("Broadcom");
I don't think Broadcom qualifies as author. This should be the name of
whoever wrote the code. There are a few drivers that contain the company
name in the MODULE_AUTHOR, but I don't think those are correct either.
> +MODULE_DESCRIPTION("Driver for KONA PWMC");
"Driver for KONA PWM controller"?
> +MODULE_LICENSE("GPL");
According to the header comment this should be "GPL v2".
> +MODULE_VERSION("1.0");
I don't think we need this.
Thierry
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