Hi Simon,
On 07/30/2012 08:00 PM, Simon Glass wrote:
For the delay, I think milliseconds is reasonable. I suppose there is
no reasonable need for microseconds?
I don't see any need for microseconds myself - anybody sees use for
finer-grained delays?
Btw, I noticed I was using mdelay instead of msleep - caught and fixed that.
+Device tree
+-----------
+All the same, power sequences can be encoded as device tree nodes. The following
+properties and nodes are equivalent to the platform data defined previously:
+
+ power-supply = <&mydevice_reg>;
+ enable-gpio = <&gpio 6 0>;
+
+ power-on-sequence {
+ regulator@0 {
+ id = "power";
Is there a reason not to put the phandle here, like:
id = <&mydevice_reg>;
(or maybe 'device' instead of id?)
There is one reason, but it might be a bad one. On Tegra, PWM phandle
uses an extra cell to encode the duty-cycle the PWM should have when we
call get_pwm(). This makes it possible to address the same PWM with
different phandles (and different duty cycles), which causes an issue to
know whether a PWM is already used in a sequence (potentially resulting
in multiple get_pwm calls on the same PWM, and also opens the door to
ambiguities in behavior (what is the correct duty-cycle to use if
several different values are passed?)
Maybe the problem lies in how PWM phandles are handled - if duty-cycle
was not part of the information, we would not have this problem.
+Note that first, the phandles of the regulator and gpio used in the sequences
+are defined as properties. Then the sequence references them through the id
+property of every step. The name of sub-properties defines the type of the step.
+Valid names are "regulator", "gpio" and "pwm". Steps must be numbered
+sequentially.
For the regulator and gpio types I think you only have an enable. For
the pwm, what is the intended binding? Is that documented elsewhere?
Same thing, enable/disable which would call pwm_enable and pwm_disable.
One could also image an additional property to set the duty cycle if it
can be taken off the phandle.
Also it might be worth mentioning how you get a struct power_seq from
an fdt node, and perhaps given an example of a device which has an
attached node, so we can see how it is referenced from the device
(of_parse_power_seq I think). Do put the sequence inside the device
node or reference it with a phandle?
Yes, this definitely needs more documentation - especially the DT part.
Thanks,
Alex.
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