On 7/11/24 16:46, 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>
---
...
+static int adt7475_pwm_properties_parse_reference_args(struct fwnode_handle *fwnode,
+ struct adt7475_pwm_config *cfg)
+{
+ int ret;
+ struct fwnode_reference_args args = {};
+ int freq_hz;
+ int duty;
+
+ ret = fwnode_property_get_reference_args(fwnode, "pwms", "#pwm-cells", 0, 0, &args);
+ if (ret)
+ return ret;
+
+ if (args.nargs != 4) {
+ fwnode_handle_put(args.fwnode);
+ return -EINVAL;
+ }
+
+ freq_hz = 1000000000UL / args.args[1];
+ duty = 255 / (args.args[1] / args.args[3]);
+
You'll need to validate args.args[1] and args.args[3] to ensure that there are no
divide by 0 errors.
On a side note,
a = b / (c / d) == b / c * d (at least for d != 0)
Since the result is defined for d == 0, you'd only have to make sure
that args.args[1] > 0 and that the result for the duty cycle is <= 255.
+ cfg->index = args.args[0];
+ cfg->freq = find_closest(freq_hz, pwmfreq_table, ARRAY_SIZE(pwmfreq_table));
+ cfg->flags = args.args[2];
+ cfg->duty = clamp_val(duty, 0, 0xFF);
+
+ fwnode_handle_put(args.fwnode);
+
+ return 0;
+}
+
+static int adt7475_pwm_properties_parse_args(struct fwnode_handle *fwnode,
+ struct adt7475_pwm_config *cfg)
+{
+ int ret;
+ u32 args[4] = {};
+ int freq_hz;
+ int duty;
+
+ ret = fwnode_property_read_u32_array(fwnode, "pwms", args, ARRAY_SIZE(args));
+ if (ret)
+ return ret;
+
+ freq_hz = 1000000000UL / args[1];
+ duty = 255 / (args[1] / args[3]);
+
+ cfg->index = args[0];
+ cfg->freq = find_closest(freq_hz, pwmfreq_table, ARRAY_SIZE(pwmfreq_table));
+ cfg->flags = args[2];
+ cfg->duty = clamp_val(duty, 0, 0xFF);
+
The code above is duplicate; please combine into a single function
(I don't mind if it has four parameters).
Thanks,
Guenter
