On Mon, Jul 22, 2024 at 04:09:46PM +1200, Chris Packham wrote: > > On 22/07/24 15:53, Guenter Roeck wrote: > > On 7/21/24 17:58, Chris Packham wrote: > > > By default the PWM duty cycle in hardware is 100%. On some systems this > > > can cause unwanted fan noise. Add the ability to specify the fan > > > connections and initial state of the PWMs via device properties. > > > > > > Signed-off-by: Chris Packham <chris.packham@xxxxxxxxxxxxxxxxxxx> > > > --- > > > > > > Notes: > > > Changes in v6: > > > - Use do_div() instead of plain / > > > - Use a helper function to avoid repetition between the of and > > > non-of > > > code paths. > > > Changes in v5: > > > - Deal with PWM frequency and duty cycle being specified in > > > nanoseconds > > > Changes in v4: > > > - Support DT and ACPI fwnodes > > > - Put PWM into manual mode > > > Changes in v3: > > > - Use the pwm provider/consumer bindings > > > Changes in v2: > > > - Use correct device property string for frequency > > > - Allow -EINVAL and only warn on error > > > - Use a frequency of 0 to indicate that the hardware should be > > > left as-is > > > > > > drivers/hwmon/adt7475.c | 130 ++++++++++++++++++++++++++++++++++++++++ > > > 1 file changed, 130 insertions(+) > > > > > > diff --git a/drivers/hwmon/adt7475.c b/drivers/hwmon/adt7475.c > > > index 4224ffb30483..fc5605d34f36 100644 > > > --- a/drivers/hwmon/adt7475.c > > > +++ b/drivers/hwmon/adt7475.c > > > @@ -21,6 +21,8 @@ > > > #include <linux/of.h> > > > #include <linux/util_macros.h> > > > +#include <dt-bindings/pwm/pwm.h> > > > + > > > /* Indexes for the sysfs hooks */ > > > #define INPUT 0 > > > @@ -1662,6 +1664,130 @@ static int adt7475_set_pwm_polarity(struct > > > i2c_client *client) > > > return 0; > > > } > > > +struct adt7475_pwm_config { > > > + int index; > > > + int freq; > > > + int flags; > > > + int duty; > > > +}; > > > + > > > +static int _adt7475_pwm_properties_parse_args(u32 args[4], struct > > > adt7475_pwm_config *cfg) > > > +{ > > > + unsigned long freq_hz; > > > + unsigned long duty; > > > + > > > + if (args[1] == 0) > > > + return -EINVAL; > > > + > > > + freq_hz = 1000000000UL; > > > + do_div(freq_hz, args[1]); > > > + duty = 255 * args[3]; > > > + do_div(duty, args[1]); > > > + > > > > Gues I am a bit at loss here, just as 0-day. Why use do_div ? It is only > > needed > > for 64-bit divide operations. > > Mainly because of Uwe's comment on v5. I think I've avoided the original u64 > issue now that I'm converting fwnode_reference_args::args to a u32 array. My comment was only about the build bot finding a division where the gcc stub was missing with is an indication that do_div should be used. Usually for PWMs perdiod and duty_cycle are u64, but here it's only about values from the dtb, so they are u32 and a plain / should be fine. > can probably get away with plain division, although 255 * args[3] / args[1] > might overflow in theory but shouldn't in practice. I don't like possible overflows, but I don't care enough for hwmon drivers to object. Still a check for args[3] <= 0x1010101 would be easy enough. Best regards Uwe
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