Re: [PATCH 2/2] tty: serial core: use the ACPI PM state defines

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On Fri, Dec 7, 2012 at 12:36 AM, Alan Cox <alan@xxxxxxxxxxxxxxx> wrote:

> What about just using 0, 1, 2, 3 to indicate states similar to D0-D3
> which as a base concept everyone is familiar with ?

Sorry, I might be something of an oddity, but ACPI is not used on
ARM systems as of today, and I was completely confused by
these:

  uart_change_pm(state, 0);
  uart_change_pm(state, 3);

I was just like ... eh ... 0? 3?

No ACPI associations existed in my head until I finally found
the note in the documentation saying that it corresponds to
ACPI states.

We are a few kernel developers these days who never ever
worked on Intel, sorry for this, but that's what we are like :-)

> If we need something more than that, then can we talk about what the
> actual extra non 0/3 states needed are and how to get a generic
> meaningful definition, or indeed whether a number rather than flag bits
> makes sense ?

Sure, I think my colleague Rickard will soon post another
patch for controlling the state 1,2 bottom-up from drivers.

> Start with the driver/platform that causes the concern and then the
> rest is probably blindingly obvious.

It's the introduction of runtime power management for the ARM
amba-pl011.c UART driver that confuse us.

It is atleast obvious that none of the 5 ARM platforms using that
driver do not use ACPI, and I expect the situation to be the same
for most of the ARM drivers.

Yours,
Linus Walleij
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