Re: [Xen-devel] [PATCH 3/4] xen: set the right flags when enabling interrupts for 8250

[Chen Baozi <baozich@xxxxxxxxx>]

On Jul 26, 2013, at 9:14 AM, Chen Baozi <baozich@xxxxxxxxx> wrote:

> 
> On Jul 25, 2013, at 8:33 PM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
> 
>> On 07/25/2013 12:31 PM, Chen Baozi wrote:
>>> 
>>> On Jul 25, 2013, at 7:17 PM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
>>> 
>>>> On 07/25/2013 10:14 AM, Chen Baozi wrote:
>>>> 
>>>>> Besides this test, I noticed that we set a timer to poll UART after 
>>>>> enabling
>>>>> the interrupt. And the timer initialization codes are platform specific, 
>>>>> which
>>>>> should be implemented in xen/arch/arm/platforms/omap5.c for example. 
>>>>> However,
>>>>> I haven't done this yet. (I used to plan to turn to this work after UART 
>>>>> porting
>>>>> has been done.) Is it a possible factor that may cause my issues?
>>>> 
>>>> Xen uses the arch timers to handle the time. On some platform (for
>>>> instance the Arndale), it's not enabled by default.
>>>> 
>>>> If the omap5 boot with the arch timers enabled, you don't need to
>>>> implement the init_time callback.
>>>> 
>>>> Do you know if Xen receives timer interrupts?
>>> 
>>> Any way that I could confirm this?
>>> 
>>> There is a line of boot message:
>>> 
>>> "Using generic timer at 0 KHz."
>>> 
>> 
>> It seems the arch timer is not configured/enabled. Do you know if U-boot
>> enables it?
> 
> I could see clocks.c/clocks.o in its u-boot sources, but I don't think U-boot 
> has already enabled it, for I could read such lines from Linux kernel boot 
> messages:
> 
> """
> OMAP clockevent source: GPTIMER1 at 32768 Hz
> sched_clock: 32 bits at 32kHz, resolution 30517ns, wraps every 131071999s
> OMAP clocksource: 32k_counter at 32768 Hz
> arch_timer: No interrupt available, giving up
> omap5_realtime_timer_init: arch_timer_register failed -22
> 
>> 
>> It's not clear to me, how you need to implement init_time. Do you have a
>> datasheet with the board? If yes, is there a section for the section timer?
> 
> Yes, TI has published an 49.6MB Technical Reference Manual online with 88 
> pages section about timer.

Wait. I think I might make a mistake. The "arch timer" is different from 
"timer" as devices, right? The timer section in Technical Reference Manual 
seems to be the latter one, for it is  connect to the Level-4 interconnect of 
OMAP5432 and described as "ti,omap5430-timer" in DTS. I think the "arch timer" 
you mentioned should refer to "arm,armv7-timer", right?

> 
>> 
>> Perhaps the good start is linux/arch/arm/mach-omap2/timer.c.
> 
> Thanks a lot, it should be helpful!
> 
> Baozi
> 


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