Hi Kevin,

On Wed, Nov 9, 2011 at 12:50 AM, Kevin Hilman [off-list ref] wrote:

Rajendra Nayak [off-list ref] writes:

quoted

Hi Kevin,

On Saturday 05 November 2011 04:12 AM, Kevin Hilman wrote:

quoted

However, as mentioned previously[1], due to a HW sleepdep between MPU
and CORE, this constraint isn't actually needed for CORE UARTs, so it's
a bit wasteful to go through all the constraint setting for no reason.

I had a short chat with Govind on this and was trying to understand
this better.
Are you referring to the 'autodeps' for omap3 here, because they would
prevent any clock domain from idling as long as MPU or IVA are active,

No, I was thinking of HW sleepdeps. ?However, I looked back at the
OMAP3430 TRM and see that MPU does not have a HW sleepdep on CORE like I
thought.

quoted

but not the other way round. Which means MPU can still idle, while CORE
does not.

My guess was, its probably the CORE domain idling itself thats causing
the UART sluggishness, (and not MPU idling), due to higher latency,
which is prevented with an active UART module in CORE, but not in PER.

OK, that indeed makes sense. ?Thanks for correcting me.

quoted

So Govind did a small experiment to prevent just CORE idling and let MPU
idle alone and that did not show any sluggishness.

OK, good.

quoted

Now, putting a pm-qos constraint for a UART in CORE still looks
redundant because the latency requirement that UART has is in
some way *indirectly* met (because the active UART in CORE prevents
CORE transitions in idle).
But don't you think the UART driver should express its
latency constraints regardless, without thinking of any indirect ways
in which the same requirements would have already been met?

Yes, you're right. ?The driver should not need to know which powerdomain
a given UART is in. ?It's probably best (and most portable) to have UART
always express its requirements all the time.

Thanks for digging into this,

I have fixed this and other uart_v7 comments and have re-based the
patch series on top
of 3.2-rc1 along with Tero's v9 irq chaining patches and tested the same.
Available here [1].

Can this patches series be added to a test branch for upstreaming or do you
think there are still some outstanding comments that needs to be discussed?

--
Thanks,
Govindraj.R

[1]:

git://gitorious.org/runtime_3-0/runtime_3-0.git
3.2-rc1_uart_runtime