Hi Thierry,
(2015/08/17 23:15), Thierry Reding wrote:
> Sorry for taking an awful long time to get around to this. The driver
> looks generally okay, but I have a few minor comments...
Thank you for the review!
> On Mon, Jun 15, 2015 at 06:08:44PM +0900, Yoshihiro Shimoda wrote:
>> This patch adds support for R-Car SoCs PWM Timer.
>
> This could be a little more verbose. You could say for example how many
> channels the driver exposes, or mention typical use-cases (if any).
Yes, I will add the following comment.
The PWM timer of R-Car H2 has 7 channels. So, we can use the channels if we
describe device tree nodes.
>> diff --git a/drivers/pwm/pwm-rcar.c b/drivers/pwm/pwm-rcar.c
> [...]
>> +static int rcar_pwm_get_clock_division(struct rcar_pwm_chip *rp, int
>> period_ns)
>> +{
>> + int div;
>
> Can be unsigned int.
I will fix it.
>> + unsigned long clk_rate = clk_get_rate(rp->clk);
>> + unsigned long long max; /* max cycle / nanoseconds */
>> +
>> + if (!clk_rate)
>
> I prefer it when these are explicit: clk_rate == 0. This goes for
> numerical comparisons. For booleans, or NULL pointer comparisons the
> !expression is fine.
I will fix it.
>> +static int rcar_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
>> + int duty_ns, int period_ns)
>> +{
>> + struct rcar_pwm_chip *rp = to_rcar_pwm_chip(chip);
>> + int div = rcar_pwm_get_clock_division(rp, period_ns);
>> + int ret;
>> +
>> + if (div < 0)
>> + return div;
>> +
>> + /* Let the core driver set pwm->period if disabled and duty_ns == 0 */
>> + if (!test_bit(PWMF_ENABLED, &pwm->flags) && !duty_ns)
>> + return 0;
>> +
>> + rcar_pwm_bit_modify(rp, RCAR_PWMCR_SYNC, RCAR_PWMCR_SYNC, RCAR_PWMCR);
>> + ret = rcar_pwm_set_counter(rp, div, duty_ns, period_ns);
>> + rcar_pwm_set_clock_control(rp, div);
>> + rcar_pwm_bit_modify(rp, RCAR_PWMCR_SYNC, 0, RCAR_PWMCR);
>> +
>> + return ret;
>> +}
>> +
>> +static int rcar_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
>> +{
>> + struct rcar_pwm_chip *rp = to_rcar_pwm_chip(chip);
>> + u32 pwmcnt;
>> +
>> + /* Don't enable the PWM device if CYC0 or PH0 is 0 */
>> + pwmcnt = rcar_pwm_read(rp, RCAR_PWMCNT);
>> + if (!(pwmcnt & RCAR_PWMCNT_CYC0_MASK) ||
>> + !(pwmcnt & RCAR_PWMCNT_PH0_MASK))
>> + return -EINVAL;
>
> This looks wrong. Any errors in configuration should've been caught by
> the ->config() implementation. Why can't you return -EINVAL on this
> condition in ->config()? ->enable() failing should only be the case if
> truly the PWM can't be enabled, not if it's badly configured.
I would like to avoid a "prohibition setting" when the PWM is enabled.
The datasheet said "setting 0x000 is prohibited" in CYC0 and PH0.
However, the initial value of each field is 0x000.
So, I am thinking this is truly the PWM can't be enabled.
If this driver sets any value to the register in probe() to avoid
"prohibition setting", I can remove the condtion in ->enable().
What do you think?
About the ->config(), it already has such a condition check by
rcar_pwm_set_counter():
+ /* Avoid prohibited setting */
+ if (cyc && ph)
+ rcar_pwm_write(rp, cyc | ph, RCAR_PWMCNT);
+
+ return (cyc && ph) ? 0 : -EINVAL;
However it may be unreadable code. So, I will fix it as the followings:
+ /* Avoid prohibited setting */
+ if (cyc != 0 && ph != 0) {
+ rcar_pwm_write(rp, cyc | ph, RCAR_PWMCNT);
+ return 0;
+ } else {
+ return -EINVAL;
+ }
>> +static struct platform_driver rcar_pwm_driver = {
>> + .probe = rcar_pwm_probe,
>> + .remove = rcar_pwm_remove,
>> + .driver = {
>> + .name = "pwm-rcar",
>> + .of_match_table = of_match_ptr(rcar_pwm_of_table),
>> + }
>> +};
>
> This doesn't need the artificial padding. A single space around = is
> enough.
I will fix it.
Best regards,
Yoshihiro Shimoda
> Thierry
>
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