* Anyone implement Cortex A9 FIQ
@ 2013-03-15 7:38 Frank Li
2013-03-15 10:46 ` Jonathan Austin
0 siblings, 1 reply; 7+ messages in thread
From: Frank Li @ 2013-03-15 7:38 UTC (permalink / raw)
To: linux-arm-kernel
All:
Recently, we need real time work run in cortex A9.
Did anyone use FIQ on Cortex A9?
best regards
Frank Li
^ permalink raw reply [flat|nested] 7+ messages in thread
* Anyone implement Cortex A9 FIQ
2013-03-15 7:38 Anyone implement Cortex A9 FIQ Frank Li
@ 2013-03-15 10:46 ` Jonathan Austin
2013-03-17 1:15 ` Frank Li
0 siblings, 1 reply; 7+ messages in thread
From: Jonathan Austin @ 2013-03-15 10:46 UTC (permalink / raw)
To: linux-arm-kernel
Hi Frank,
On 15/03/13 07:38, Frank Li wrote:
> All:
> Recently, we need real time work run in cortex A9.
> Did anyone use FIQ on Cortex A9?
>
What are you actually trying to do? There's quite a lot more complexity
to being able to do real-time work on an A-class processor than just
using FIQ, and much of that would be platform specific. For example on
ARMv7A, we generally can't assume that FIQ can be used by the non-secure
world...
Jonny
^ permalink raw reply [flat|nested] 7+ messages in thread
* Anyone implement Cortex A9 FIQ
2013-03-15 10:46 ` Jonathan Austin
@ 2013-03-17 1:15 ` Frank Li
2013-03-18 19:02 ` Jonathan Austin
0 siblings, 1 reply; 7+ messages in thread
From: Frank Li @ 2013-03-17 1:15 UTC (permalink / raw)
To: linux-arm-kernel
2013/3/15 Jonathan Austin <jonathan.austin@arm.com>:
> Hi Frank,
>
>
> On 15/03/13 07:38, Frank Li wrote:
>>
>> All:
>> Recently, we need real time work run in cortex A9.
>> Did anyone use FIQ on Cortex A9?
>>
>
> What are you actually trying to do? There's quite a lot more complexity to
> being able to do real-time work on an A-class processor than just using FIQ,
> and much of that would be platform specific. For example on ARMv7A, we
> generally can't assume that FIQ can be used by the non-secure world...
There are period task run every 125us.
Task is quick simply, just put virtual multi DMA queue to real DMA queue.
Small memory copy and set some hardware register.
>
>
> Jonny
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Anyone implement Cortex A9 FIQ
2013-03-17 1:15 ` Frank Li
@ 2013-03-18 19:02 ` Jonathan Austin
2013-03-19 7:49 ` Frank Li
0 siblings, 1 reply; 7+ messages in thread
From: Jonathan Austin @ 2013-03-18 19:02 UTC (permalink / raw)
To: linux-arm-kernel
On 17/03/13 01:15, Frank Li wrote:
> 2013/3/15 Jonathan Austin <jonathan.austin@arm.com>:
>> Hi Frank,
>>
>>
>> On 15/03/13 07:38, Frank Li wrote:
>>>
>>> All:
>>> Recently, we need real time work run in cortex A9.
>>> Did anyone use FIQ on Cortex A9?
>>>
>>
>> What are you actually trying to do? There's quite a lot more complexity to
>> being able to do real-time work on an A-class processor than just using FIQ,
>> and much of that would be platform specific. For example on ARMv7A, we
>> generally can't assume that FIQ can be used by the non-secure world...
>
> There are period task run every 125us.
> Task is quick simply, just put virtual multi DMA queue to real DMA queue.
> Small memory copy and set some hardware register.
>
Whether this is feasible will really depend on what platform you're on -
if there's a secure monitor then FIQs are out of the question anyway.
Can you tell us more about the system?
If your average interrupt latency is low then you should just be able to
do this with normal IRQs (have you got threaded interrupt handlers?)
What is it about the situation that leads you to believe that you *need*
FIQ?
Jonny
^ permalink raw reply [flat|nested] 7+ messages in thread
* Anyone implement Cortex A9 FIQ
2013-03-18 19:02 ` Jonathan Austin
@ 2013-03-19 7:49 ` Frank Li
2013-04-08 16:28 ` Dave Martin
0 siblings, 1 reply; 7+ messages in thread
From: Frank Li @ 2013-03-19 7:49 UTC (permalink / raw)
To: linux-arm-kernel
>
> Whether this is feasible will really depend on what platform you're on - if
> there's a secure monitor then FIQs are out of the question anyway. Can you
> tell us more about the system?
Freescale MX6Q.
>
> If your average interrupt latency is low then you should just be able to do
> this with normal IRQs (have you got threaded interrupt handlers?)
Not all drivers use threaded interrupt handler.
>
> What is it about the situation that leads you to believe that you *need*
> FIQ?
FIQ can be executed even in spin_lock_saveirq.
We want do very small hardware set at related precision period (every 125us).
>
> Jonny
>
>
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Anyone implement Cortex A9 FIQ
2013-03-19 7:49 ` Frank Li
@ 2013-04-08 16:28 ` Dave Martin
[not found] ` <CAHrpEqR35v76qif0wP=1SNOThLvmzpmEHcbehSNoY7-CO0CRqQ@mail.gmail.com>
0 siblings, 1 reply; 7+ messages in thread
From: Dave Martin @ 2013-04-08 16:28 UTC (permalink / raw)
To: linux-arm-kernel
On Tue, Mar 19, 2013 at 03:49:50PM +0800, Frank Li wrote:
> >
> > Whether this is feasible will really depend on what platform you're on - if
> > there's a secure monitor then FIQs are out of the question anyway. Can you
> > tell us more about the system?
>
> Freescale MX6Q.
>
> >
> > If your average interrupt latency is low then you should just be able to do
> > this with normal IRQs (have you got threaded interrupt handlers?)
>
> Not all drivers use threaded interrupt handler.
>
> >
> > What is it about the situation that leads you to believe that you *need*
> > FIQ?
>
> FIQ can be executed even in spin_lock_saveirq.
> We want do very small hardware set at related precision period (every 125us).
Why is the latency requirement so tight for this one interrupt?
Cheers
---Dave
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2013-04-10 11:10 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2013-03-15 7:38 Anyone implement Cortex A9 FIQ Frank Li
2013-03-15 10:46 ` Jonathan Austin
2013-03-17 1:15 ` Frank Li
2013-03-18 19:02 ` Jonathan Austin
2013-03-19 7:49 ` Frank Li
2013-04-08 16:28 ` Dave Martin
[not found] ` <CAHrpEqR35v76qif0wP=1SNOThLvmzpmEHcbehSNoY7-CO0CRqQ@mail.gmail.com>
2013-04-10 11:10 ` Dave Martin
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