Re: OMAP34xx

Kevin Hilman
2012-02-08T00:53:59Z

Kevin Hilman <khilman@ti.com> writes:

> Tony Lindgren <tony@atomide.com> writes:
>
> [...]
>
>>> > > --- a/arch/arm/mach-omap2/pm34xx.c
>>> > > +++ b/arch/arm/mach-omap2/pm34xx.c
>>> > > @@ -420,7 +420,7 @@ static void omap3_pm_idle(void)
>>> > > {
>>> > > local_fiq_disable();
>>> > >
>>> > > - if (omap_irq_pending())
>>> > > + if (omap_irq_pending() || 1)
>>> > > goto out;
>>> > >
>>> > > trace_power_start(POWER_CSTATE, 1, smp_processor_id());
>>> >
>>> > This does not look right to me. I thought reverting of the serial
>>> > patches should have already solved the issue you're seeing with
>>> > slow serial port?
>>> >
>>> > Those are the reverting commits drivers/tty/serial/serial-omap.c:
>>> >
>>> > 8a74e9ffd97dc9de063de8c02ae32db79dd60436 (Revert "tty: serial: OMAP: ensure
>>> > FIFO levels are set correctly in non-DMA mode")
>>> >
>>> > af681cad3f79ad8f7bd6cb170b70990aeef74233 (Revert "tty: serial: OMAP: transmit
>>> > FIFO threshold interrupts don't wake the chip")
>>>
>>> These commits have absolutely nothing to do with it. I pointed out the
>>> bad commit in one of my emails:
>>>
>>> commit 2fd149645eb46d26130d7070c6de037dddf34880
>>> Author: Govindraj.R <govindraj.raja@ti.com>
>>> Date: Wed Nov 9 17:41:21 2011 +0530
>>>
>>> ARM: OMAP2+: UART: Remove omap_uart_can_sleep and add pm_qos
>>>
>>> Omap_uart_can_sleep function blocks system wide low power state until
>>> uart is active remove this func and add qos requests to prevent
>>> MPU from transitioning.
>>>
>>> Keep qos request to default value which will allow MPU to transition
>>> and while uart baud rate is available calculate the latency value
>>> from the baudrate and use the same to hold constraint while uart clocks
>>> are enabled, and if uart is auto-idled the constraint is updated with
>>> default constraint value allowing MPU to transition.
>>>
>>> Qos requests are blocking notifier calls so put these requests to
>>> work queue, also the driver uses irq_safe version of runtime API's
>>> and callbacks can be called in interrupt disabled context.
>>> So to avoid warn on slow path warning while using qos update
>>> API's from runtime callbacks use the qos_work_queue.
>>>
>>> During bootup the runtime_resume call backs might not be called and runtime
>>> callback gets called only after uart is idled by setting the autosuspend
>>> timeout. So qos_request from runtime resume callback might not activated during
>>> boot if uart baudrate is calculated during bootup for console uart, so schedule
>>> the qos_work queue once we calc_latency while configuring the uart port.
>>>
>>> Flush and complete any pending qos jobs in work queue while suspending.
>>>
>>> Signed-off-by: Govindraj.R <govindraj.raja@ti.com>
>>> Acked-by: Greg Kroah-Hartman <gregkh@suse.de> (for drivers/tty changes)
>>> Signed-off-by: Kevin Hilman <khilman@ti.com>
>>>
>>> Basically, it looks like the OMAP 3 UART is not delivering transmit IRQs
>>> while in some of the deeper low power modes.
>>>
>>> I tried reverting the rest of the patches between this one and HEAD for
>>> omap-serial.c, but they have no effect what so ever on this bug. As I
>>> said in one of my emails in this thread, the above commit can't be
>>> trivially reverted because some other stuff that the code relied upon
>>> has vanished.
>>>
>>> So, the above along with the other part in arch/arm/mach-omap2/cpuidle34xx.c
>>> is the smallest 'fix' I could find if resolving the regression.
>>
>> OK, thanks, that should be enough info for let Kevin take a look at this.
>
> This one is indeed strange. I have not seen this on the 34xx devices
> I'm using (3430/n900, 3530/Overo, 3630/Zoom3).

OK, I've reproduced this on v3.3-rc2.

The reason I wasn't seeing this is because I'm using the fixes Paul has
already posted that fix this problem:

http://marc.info/?l=linux-arm-kernel&m=132754676814391&w=2

Kevin