On Mon, 08 Jun 2020, Michael Walle wrote:

Am 2020-06-08 20:56, schrieb Lee Jones:

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On Mon, 08 Jun 2020, Michael Walle wrote:

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Am 2020-06-08 12:02, schrieb Andy Shevchenko:

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+Cc: some Intel people WRT our internal discussion about similar
problem and solutions.

On Mon, Jun 8, 2020 at 11:30 AM Lee Jones [off-list ref] wrote:

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On Sat, 06 Jun 2020, Michael Walle wrote:

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Am 2020-06-06 13:46, schrieb Mark Brown:

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On Fri, Jun 05, 2020 at 10:07:36PM +0200, Michael Walle wrote:

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Am 2020-06-05 12:50, schrieb Mark Brown:

...

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Right.  I'm suggesting a means to extrapolate complex shared and
sometimes intertwined batches of register sets to be consumed by
multiple (sub-)devices spanning different subsystems.

Actually scrap that.  The most common case I see is a single Regmap
covering all child-devices.

Yes, because often we need a synchronization across the entire address
space of the (parent) device in question.

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 It would be great if there was a way in
which we could make an assumption that the entire register address
space for a 'tagged' (MFD) device is to be shared (via Regmap) between
each of the devices described by its child-nodes.  Probably by picking
up on the 'simple-mfd' compatible string in the first instance.

Rob, is the above something you would contemplate?

Michael, do your register addresses overlap i.e. are they intermingled
with one another?  Do multiple child devices need access to the same
registers i.e. are they shared?

No they don't overlap, expect for maybe the version register, which is
just there once and not per function block.

Then what's stopping you having each device Regmap their own space?

Because its just one I2C device, AFAIK thats not possible, right?

Not sure what (if any) the restrictions are.

I can't think of any reasons why not, off the top of my head.

Does Regmap only deal with shared accesses from multiple devices
accessing a single register map, or can it also handle multiple
devices communicating over a single I2C channel?

One for Mark perhaps.

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The issues I wish to resolve using 'simple-mfd' are when sub-devices
register maps overlap and intertwine.

[...]

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What do these bits configure?

- hardware strappings which have to be there before the board powers
up,
  like clocking mode for different SerDes settings
- "keep-in-reset" bits for onboard peripherals if you want to save
power
- disable watchdog bits (there is a watchdog which is active right
from
  the start and supervises the bootloader start and switches to
failsafe
  mode if it wasn't successfully started)
- special boot modes, like eMMC, etc.

Think of it as a 16bit configuration word.

And you wish for users to be able to view these at run-time?

And esp. change them.

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Can they adapt any of them on-the-fly or will the be RO?

They are R/W but only will only affect the board behavior after a reset.

I see.  Makes sense.  This is board controller territory.  Perhaps
suitable for inclusion into drivers/soc or drivers/platform.

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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