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 6:42 PM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:

> On 07/26/2013 04:31 AM, Chen Baozi wrote:
>> 
>> 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:
> 
> Are you trying to boot Linux on bare metal or as dom0?

bare metal.

> 
>>> """
>>> 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
> 
> Do you have a "arm,armv7-timer" compatible node in your DTS with
> interrupts? Here Linux can't find an appropriate interrupt.

You reminds me that the DTS shipped along with the board has issues on 
"arm,armv7-timer". I have corrected it for xen but leave the bare metal booting 
dtb the original status.

> 
>>> 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?
> 
> By "arch timer" I mean "arm,armv7-timer".

Thanks. So I think the codes to start with it is 
linux/drivers/clocksource/arm_arch_timer.c: arch_timer_init(). The 
linux/arch/arm/mach-omap2/timer.c is for the timer device "ti,omap543-timer".

Again, Thanks a lot.

Baozi
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