Re: [PATCH 1/3] mfd: pm8921: Expose pm8xxx_read_irq_status

From: Bjorn Andersson
Date: Wed Jul 09 2014 - 10:13:43 EST

On Wed, Jul 9, 2014 at 12:59 AM, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
> On Tue, Jul 8, 2014 at 3:26 AM, Bjorn Andersson
> <bjorn.andersson@xxxxxxxxxxxxxx> wrote:
>> Most status bits, e.g. for GPIO and MPP input, is retrieved by reading
>> the interrupt status registers, so this needs to be exposed to clients.
>> Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxxxxxx>
> Hm do you mean you read the input *values* from the interrupt status
> registers?

Due to the limited address space (I presume), many of the status bits
on the pm8xxx are not exposed in any other place than through a banked
register in the interrupt "block". So we have to read the interrupt
status in order to get information related to things like gpio status
or if a battery is present for charging.

> What madness in that case.... :-)


> Anyway, since the driver is based on regmap, can't the children just
> get a regmap * somehow and then just go read the same register
> instead of having to add a special function for it?

That we have, and we have access to that part of the ssbi address
space. Unfortunately, like everything else in these pmics, things are
banked. So we need first a bank selector and then a read; so it's racy
with the interrupt handler code doing the same thing.

> When I look at it it seems like it's doing regmap strangely or
> something, like it's one write then one read operation to get
> the register(s) and isn't that all supposed to be hidden behind
> regmap so you don't need the local lock chip->pm_irq_lock?

I guess one could have exposed a regmap that instead of exposing the
ssbi address space presented a logical view of the pm8xxx registers;
something like the bitplanes on Amiga. I prefer having a ssbi regmap
for simplicity (and sanity) but then we need to have this read in the
irq driver.

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