On Tuesday 08 November 2016 08:12 PM, Thierry Reding wrote:
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On Tue, Nov 08, 2016 at 07:05:26PM +0530, Laxman Dewangan wrote:
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.
It looks as if regulator notifiers should be able to support whatever
use-cases we may have (I suspect that we really only need pre- and post-
voltage-change notifications.
Yes, we have pre/post and abort notification from regulator.
REGULATOR_EVENT_PRE_VOLTAGE_CHANGE,
REGULATOR_EVENT_ABORT_VOLTAGE_CHANGE,
REGULATOR_EVENT_VOLTAGE_CHANGE,
So it can be done dynamically.
As the notification is atomic context, we need to support atomic context
of pmc register configurations.
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 static configurations where we have a regulator along with a pinmux
setting for the I/O voltage we could potentially run into issues where
both settings don't match. How would we handle that?
As a process, we are generating the IO pad control DT configuration from
the customer pinmux spreadsheet. So there is data population by hardware
(system eng) team and SW just use the auto-generated dtsi file in SW.
This avoided the error/mistake created by the SW engineer.
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.
Are patches available for this? It'd be useful to know how this will end
up being used in order to come up with the best solution.
In general I think it's good to send a complete series of patches, even
if it's long and spans multiple subsystems. As it is it's difficult for
anyone else (myself included) to understand where this is headed, which
makes it more complicated than necessary to get at the final solution.
The dynamic setting is used by mmc driver and it is handled by mmc team.
They are waiting for framework/infrastructure to be available for their
patches.
However, in downstream, we have all these implemented. In downstram we
have pad control driver but instead of new framework, we decided to do
it through pinctrl framework.
So if you look for mmc driver in downstream, you can get the actual
code about usage.
However, for clarity, here is sequence:
1. Voltage from 3.3V to 1.8V
ret = regulator_set_voltage(regulator, 1800000, 1800000);
if (!ret)
ret = padctrl_set_voltage(padctrl, 1800000);
2. Voltage from 1.8V to 3.3V
ret = padctrl_set_voltage(padctrl, 3300000);
if (!ret)
ret = regulator_set_voltage(regulator, 3300000, 3300000);
With pinctrl framework, the APIs will be
pinctrl_lookup_state(pinctrl, "io-pad-3v3");
or
pinctrl_lookup_state(pinctrl, "io-pad-1v8");
The static setting is doen during initialization of the driver.
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).
Again, it would be best to see this in actual use. Right now it's not
clear that we'll even have both cases. Implementing both approaches will
mean potentially unused code.
We can have the only one say regulator approach then it will be
mandatory to have regulator nodes for all vdd-io so that io-pads are
configured properly.
In the probe, it will get regulator and if found the get_voltage and
configure pmc.
I am thinking about supporting IO pad configuration(static) in case we
do not have regulator enabled/up in platform and want to set IO pads
manually from DT.
On another note: in my experience you seldom need both cases, since the
dynamic configuration is the hard one, and the static configuration will
usually be a special case of the dynamic configuration.
Cases will be with regulator support available or not.
So if we donot want to support the cases, where actual regualator
support is not available then we will not need to set IO pads voltage
via DT framework.
However, we will still needs low-power support from pinctrl framework.
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