On Tuesday 08 November 2016 06:59 PM, Linus Walleij wrote:
On Tue, Nov 8, 2016 at 11:20 AM, Laxman Dewangan <ldewangan@xxxxxxxxxx> wrote:
On Tuesday 08 November 2016 03:45 PM, Linus Walleij wrote:
If you can *actually* change the volatage, it needs to be modeled
as a (fixed voltage?) regulator, not as a custom property for the pin
control attributes. I guess you definiately need the regulator framework
to accumulate and infer the different consumer requirements anyway
in that case.
The PMIC voltage output is changed via regulator calls.
Here, we need to have two configruations for given voltage level of
interface:
* One at IO voltage from PMIC via regulator call to change votlage of IO
rail.
* Second, configure the IO pad register to tell the IO voltage level so that
it can configured internally for that level.
I understand! (I think.)
Thanks,
But then the two things (A) changing the regulator voltage and (B) changing
the pin setting need to happen at the same time do they
not?
Now you're just hardcoding something into these device tree properties
and hoping that the regulators will somehow be set up in accordance to
what you set up for the pads in the device tree, correct?
There is two types of configuration in given platform, the IO voltage
does not get change (fixed in given platform) and in some of cases, get
change dynamically like SDIO3.0 where the voltage switches to 3.3V and 1.8V.
Yes, it can be integrated with the regulator handle and then it can call
the required configurations through notifier and regulator_get_voltage().
But I think it is too much complex for the static configurations. This
mandate also to populate the regulator handle and all power tree.
The simple way for static configuration (case where voltage does not get
change), just take the power tree IO voltage from DT and configure the
IO pad control register.
For dynamic case, there is some sequence need to be followed based on
voltage direction change (towards lower or towards higher) for the
voltage change and the IO pad voltage configuration and it is simple to
do it from client driver.
To me it seems like the pins/pads should all have an <&phandle> to
the regulator controlling its voltage output, in the device tree.
In the Linux kernel, the driver has to regulator_[bulk_]get() this for
each pin, check the voltage with regulator_get_voltage() and set up
this according to the supplied voltage.
The driver then ideally should subscribe to regulator voltage notifier
events to change the setting if the voltage changes. I guess. But
atleast the first step seems inevitable: get the voltage from a regulator.
Else there is no dependency between the regulator and its consumer.
So what your pins need is a regulator phandle, not a magic value to
be poked into a register, hoping things will match up.
I understand that this is a simple quick-and-dirty solution but it is
not the right solution.
Yaah, the static power tree configuration is much simple in this
approach without having regulator drivers and support.
Integrating with regulator driver can be done here also.
I like to have both approach, through pinmux DT and also from regulator.
So based on the platform, if regulator supported then populate required
properties in DT for regulator else go on standard pinmux DT way (for
non-regulator cases).
Need your opinion?
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