Re: [PATCH V2 5/6] regulator: add mxs on-chip regulator driver

Mark Brown [off-list ref] hat am 27. Mai 2015 um 19:33 geschrieben:


On Tue, May 26, 2015 at 02:16:55PM +0200, Stefan Wahren wrote:

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Mark Brown [off-list ref] hat am 7. Mai 2015 um 21:32 geschrieben:

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In the bootloader code enabling the DC-DC is critical. There is a
known
issue
which falsely triggers the brownout detection.

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Why would the driver not provide these operations?

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I didn't implement this operation because the suggested workaround for
the
hardware issue isn't very nice
(disable brownout detection during enabling DC-DC). I was afraid of the
implementation.

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That doesn't sound too complicated?

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Okay, i think i managed the brownout handling.

Unfortunately i'm stuck at the next step. The DC-DC (3 way output) can
supply 3
LDOs vddd, vdda, vddio. In case of a DC-DC state change the 3 regulators
needs
to be reconfigured before.

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I tought of REGULATOR_EVENT_PRE_DISABLE and REGULATOR_EVENT_PRE_ENABLE
events,
but i'm not sure that's the right way to achieve a synchronization between
DC-DC
and consuming LDOs.

OK, that's possibly sounding a bit complicated. Is it just a case of
writing some value, doing a reconfiguration and rewriting the original
value or is it something more?

In case of a single driver instance instead of 4 ones (vddd, vddio, vdda,
dc-dc), things would be much easier.

Here are the steps for disabling DC-DC:

1. configure vddio to work without DC-DC
2. configure vdda to work without DC-DC
3. configure vddd to work without DC-DC
4. backup DC-DC settings
5. disable brownout detection
6. disable DC-DC
7. restore DC-DC settings

My problem is that step 1 to 3 must be done step by step through the other
regulator instances.

If it's much more complicated than that
then I think putting a comment in the driver explaining what the issue
is would be the right step, that would address the issue with the driver
looking strange.

Enabling or disabling DC-DC is only needed internally by the power subsystem
(e.g. in case of handoff AC to battery), because the DC-DC only supplys the
regulator daisy. From my understanding hardware components could use only the
regulator outputs. In the end a state change is necessary, but it shouldn't be a
public.
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