On Tue, Nov 12, 2013 at 09:36:55AM +0800, Xiubo Li wrote:
> The FTM PWM device can be found on Vybrid VF610 Tower and Layerscape LS-1 SoCs.
>
> Signed-off-by: Xiubo Li <Li.Xiubo@xxxxxxxxxxxxx>
> Signed-off-by: Alison Wang <b18965@xxxxxxxxxxxxx>
> Signed-off-by: Jingchang Lu <b35083@xxxxxxxxxxxxx>
> Reviewed-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
> ---
> drivers/pwm/Kconfig | 10 ++
> drivers/pwm/Makefile | 1 +
> drivers/pwm/pwm-fsl-ftm.c | 402 ++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 413 insertions(+)
> create mode 100644 drivers/pwm/pwm-fsl-ftm.c
Sorry for taking so long. Overall this looks pretty good. A few minor
comments below.
> diff --git a/drivers/pwm/pwm-fsl-ftm.c b/drivers/pwm/pwm-fsl-ftm.c
[...]
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +#include <linux/err.h>
> +#include <linux/clk.h>
> +#include <linux/io.h>
> +#include <linux/pwm.h>
> +#include <linux/of_address.h>
Can you sort these alphabetically, please?
> +#include <dt-bindings/clock/vf610-clock.h>
This can stay separate, and I would even separate it from the others by
a blank line.
> +#define FTM_SC 0x00
> +#define FTMSC_CLK_MASK 0x03
Perhaps FTM_SC_CLK_MASK for consistency with the register name? Same for
all others below.
> +#define FTMSC_CLK_OFFSET 0x03
I think the more common suffix would be _SHIFT. _OFFSET is more
typically used for registers, not bitfields.
> +#define FTMSC_CLKSYS (0x01 << 3)
> +#define FTMSC_CLKFIX (0x02 << 3)
> +#define FTMSC_CLKEXT (0x03 << 3)
Perhaps "<< 3" should be "<< FTM_SC_CLK_SHIFT"? And the names perhaps
FTM_SC_CLK_{SYS,FIX,EXT}? That somehow "namespaces" all of them.
> +#define FTMSC_PS_MASK 0x07
> +#define FTMSC_PS_OFFSET 0x00
> +
> +#define FTM_CNT 0x04
> +#define FTM_MOD 0x08
> +
> +#define FTM_CSC_BASE 0x0C
> +#define FTM_CSC(_channel) (FTM_CSC_BASE + ((_channel) * 8))
> +#define FTMCnSC_MSB BIT(5)
Same here: FTMCnSC_MSB isn't immediately obvious to be a bit within the
FTM_CSC register. FTM_CSC_MSB is.
> +#define FTM_CNTIN_VAL 0x00
Do we really need this?
> +#define FTM_MAX_CHANNEL 8
This is used only once, so I prefer to just assign .npwm = 8 in the
driver's .probe() implementation.
> +static int fsl_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> + int ret;
> + struct fsl_pwm_chip *fpc;
> +
> + fpc = to_fsl_chip(chip);
You could assign this when declaring the fpc variable to save two lines.
> + ret = clk_prepare_enable(fpc->sys_clk);
> + if (ret)
> + return ret;
> +
> + return 0;
You can save another few lines by making this simply:
return clk_prepare_enable(fpc->sys_clk);
> +static void fsl_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> + struct fsl_pwm_chip *fpc;
> +
> + fpc = to_fsl_chip(chip);
Same comment here.
> +static int fsl_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
> + int duty_ns, int period_ns)
> +{
> + unsigned long period_cycles, duty_cycles;
I don't think there's a need for the _cycles suffix here.
> + unsigned long cntin = FTM_CNTIN_VAL;
I don't understand why this is needed. FTM_CNTIN_VAL is defined as 0 and
you never change cntin subsequently, so why not just use the literal 0
instead?
> + struct fsl_pwm_chip *fpc;
> +
> + fpc = to_fsl_chip(chip);
> +
> + period_cycles = fsl_rate_to_cycles(fpc, period_ns);
> + if (period_cycles > 0xFFFF) {
> + dev_err(chip->dev, "required PWM period cycles(%lu) overflow "
> + "16-bits counter!\n", period_cycles);
> + return -EINVAL;
> + }
> +
> + duty_cycles = fsl_rate_to_cycles(fpc, duty_ns);
> + if (duty_cycles >= 0xFFFF) {
> + dev_err(chip->dev, "required PWM duty cycles(%lu) overflow "
> + "16-bits counter!\n", duty_cycles);
> + return -EINVAL;
> + }
I'm not sure the error messages are all that useful. A -EINVAL error
code should make it pretty clear what the problem is.
> + writel(FTMCnSC_MSB | FTMCnSC_ELSB, fpc->base + FTM_CSC(pwm->hwpwm));
> +
> + writel(0xF0, fpc->base + FTM_OUTMASK);
> + writel(0x0F, fpc->base + FTM_OUTINIT);
The purpose of this eludes me. These seem to be global (not specific to
channel pwm->hwpwm) registers, so why are they updated whenever a single
channel is reconfigured?
> + writel(FTM_CNTIN_VAL, fpc->base + FTM_CNTIN);
This could become simply:
writel(0, fpc->base + FTM_CNTIN);
> + writel(period_cycles + cntin - 1, fpc->base + FTM_MOD);
> + writel(duty_cycles + cntin, fpc->base + FTM_CV(pwm->hwpwm));
And these:
writel(period - 1, fpc->base + FTM_MOD);
writel(duty, fpc->base + FTM_CV(pwm->hwpwm));
Although now that I think about it, this seems broken. The period is set
in a global register, so I assume it is valid for all channels. What if
you want to use different periods for individual channels? The way I
read this the last one to be configured will win and change the period
to whatever it wants. Other channels won't even notice.
Is there a way to set the period per channel?
> +static int fsl_counter_clock_enable(struct fsl_pwm_chip *fpc)
> +{
> + int ret;
> + unsigned long reg;
> +
> + if (fpc->counter_clk_enable++)
> + return 0;
Are you sure this is safe? I think you'll need to use either an atomic
or a mutex to lock this.
> + ret = clk_prepare_enable(fpc->counter_clk);
> + if (ret)
> + return ret;
In case clk_prepare_enable() fails, the counter_clk_enable will need to
be decremented in order to track the state correctly, doesn't it?
> +
> + reg = readl(fpc->base + FTM_SC);
> + reg &= ~((FTMSC_CLK_MASK << FTMSC_CLK_OFFSET) |
> + (FTMSC_PS_MASK << FTMSC_PS_OFFSET));
> + /* select counter clock source */
There should be an empty line between the above two.
> + switch (fpc->counter_clk_select) {
> + case VF610_CLK_FTM0:
> + reg |= FTMSC_CLKSYS;
> + break;
> + case VF610_CLK_FTM0_FIX_SEL:
> + reg |= FTMSC_CLKFIX;
> + break;
> + case VF610_CLK_FTM0_EXT_SEL:
> + reg |= FTMSC_CLKEXT;
> + break;
> + default:
> + break;
> + }
> + reg |= fpc->clk_ps;
And another one above this line.
> + writel(reg, fpc->base + FTM_SC);
I think with the proper locking in place what you should do is increment
counter_clk_enable only here. That makes avoids having to decrement the
count on error.
Similarly in fsl_counter_clock_disable() you can postpone decrementing
the count until the very end.
> +static int fsl_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> + struct fsl_pwm_chip *fpc;
> +
> + fpc = to_fsl_chip(chip);
> +
> + fsl_counter_clock_enable(fpc);
This can fail. Should the error be propagated?
> +
> + return 0;
> +}
> +
> +static void fsl_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> + struct fsl_pwm_chip *fpc;
> +
> + fpc = to_fsl_chip(chip);
> +
> + fsl_counter_clock_disable(fpc);
> +}
Same here. Since you can't propagate the error, perhaps an error message
would be appropriate here?
Also for the locking above, perhaps a good solution would be to acquire
the lock around the calls to fsl_counter_clock_{enable,disable}() so
that they can safely assume that they are called with the lock held,
which will make their implementation a lot simpler.
So what you could do is this:
static int fsl_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
struct fsl_pwm_chip *fpc = to_fsl_chip(chip);
int ret;
mutex_lock(&fpc->lock);
ret = fsl_counter_clock_enable(fpc);
mutex_unlock(&fpc->lock);
return ret;
}
And analogously for fsl_pwm_disable().
> +static int fsl_pwm_calculate_ps(struct fsl_pwm_chip *fpc)
> +{
> + unsigned long long sys_rate, counter_rate, ratio;
> +
> + sys_rate = clk_get_rate(fpc->sys_clk);
> + if (!sys_rate)
> + return -EINVAL;
> +
> + counter_rate = clk_get_rate(fpc->counter_clk);
> + if (!counter_rate) {
> + fpc->counter_clk = fpc->sys_clk;
> + fpc->counter_clk_select = VF610_CLK_FTM0;
> + dev_warn(fpc->chip.dev,
> + "the counter source clock is a dummy clock, "
> + "so select the system clock as default!\n");
> + }
> +
> + switch (fpc->counter_clk_select) {
> + case VF610_CLK_FTM0_FIX_SEL:
> + ratio = 2 * counter_rate - 1;
> + do_div(ratio, sys_rate);
> + fpc->clk_ps = ratio;
> + break;
> + case VF610_CLK_FTM0_EXT_SEL:
> + ratio = 4 * counter_rate - 1;
> + do_div(ratio, sys_rate);
> + fpc->clk_ps = ratio;
> + break;
> + case VF610_CLK_FTM0:
> + fpc->clk_ps = 7;
Even though it doesn't matter here, you should still add a break.
Otherwise if you ever modify the code in the default case, you don't
have to remember to add it in then.
> +static int fsl_pwm_parse_clk_ps(struct fsl_pwm_chip *fpc)
> +{
> + int ret;
> + struct of_phandle_args clkspec;
> + struct device_node *np = fpc->chip.dev->of_node;
> +
> + fpc->sys_clk = devm_clk_get(fpc->chip.dev, "ftm0");
> + if (IS_ERR(fpc->sys_clk)) {
> + ret = PTR_ERR(fpc->sys_clk);
> + dev_err(fpc->chip.dev,
> + "failed to get \"ftm0\" clock %d\n", ret);
> + return ret;
> + }
> +
> + fpc->counter_clk = devm_clk_get(fpc->chip.dev, "ftm0_counter");
> + if (IS_ERR(fpc->counter_clk)) {
> + ret = PTR_ERR(fpc->counter_clk);
> + dev_err(fpc->chip.dev,
> + "failed to get \"ftm0_counter\" clock %d\n",
> + ret);
> + return ret;
> + }
> +
> + ret = of_parse_phandle_with_args(np, "clocks", "#clock-cells", 1,
> + &clkspec);
> + if (ret)
> + return ret;
> +
> + fpc->counter_clk_select = clkspec.args[0];
This isn't at all pretty. But given that once you have access to a
struct clk there's no way to identify it, I don't know of a better
alternative.
> +
> + return fsl_pwm_calculate_ps(fpc);
> +}
> +
> +static int fsl_pwm_probe(struct platform_device *pdev)
> +{
> + int ret = 0;
There's no need to initialize this.
> + struct fsl_pwm_chip *fpc;
> + struct resource *res;
> +
> + fpc = devm_kzalloc(&pdev->dev, sizeof(*fpc), GFP_KERNEL);
> + if (!fpc)
> + return -ENOMEM;
> +
> + fpc->chip.dev = &pdev->dev;
> + fpc->counter_clk_enable = 0;
You use kzalloc(), so this is already be zeroed out.
> + ret = fsl_pwm_parse_clk_ps(fpc);
> + if (ret < 0)
> + return ret;
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + fpc->base = devm_ioremap_resource(&pdev->dev, res);
> + if (IS_ERR(fpc->base)) {
> + ret = PTR_ERR(fpc->base);
> + return ret;
You can simply do "return PTR_ERR(fpc->base);" here.
> + }
> +
> + fpc->chip.ops = &fsl_pwm_ops;
> + fpc->chip.of_xlate = of_pwm_xlate_with_flags;
> + fpc->chip.of_pwm_n_cells = 3;
> + fpc->chip.base = -1;
> + fpc->chip.npwm = FTM_MAX_CHANNEL;
> + ret = pwmchip_add(&fpc->chip);
There should be a blank linke between the above two.
> +static int fsl_pwm_remove(struct platform_device *pdev)
> +{
> + struct fsl_pwm_chip *fpc;
> +
> + fpc = platform_get_drvdata(pdev);
These can go on one line.
> +static const struct of_device_id fsl_pwm_dt_ids[] = {
> + { .compatible = "fsl,vf610-ftm-pwm", },
> + { /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, fsl_pwm_dt_ids);
> +
> +static struct platform_driver fsl_pwm_driver = {
> + .driver = {
> + .name = "fsl-ftm-pwm",
> + .owner = THIS_MODULE,
> + .of_match_table = of_match_ptr(fsl_pwm_dt_ids),
No need for of_match_ptr() since you depend on OF. And while at it, you
can drop the initialization of .owner as well, since the core takes care
of initializing that nowadays.
Thierry
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