On 7/21/24 21:09, 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. I can probably get away with plain division, although 255 * args[3] / args[1] might overflow in theory but shouldn't in practice.
I'll let the earth turn and send out a v7 that uses plain division unless someone has a strong opinion that I should sprinkle some more u64s around.
You lost me, sorry. Neither duty nor freq_hz are u64. What u64 variables
are you talking about ? Using so_div doesn't make those variables u64.
Guenter
Thanks,
Guenter
