* A question about Cortex-A73 erratum 858921
@ 2022-09-09 7:31 Kunkun Jiang
2022-09-09 12:23 ` Marc Zyngier
0 siblings, 1 reply; 3+ messages in thread
From: Kunkun Jiang @ 2022-09-09 7:31 UTC (permalink / raw)
To: Mark Rutland, Marc Zyngier, Daniel Lezcano, Thomas Gleixner
Cc: wanghaibin.wang, Zenghui Yu,
moderated list:ARM ARCHITECTED TIMER DRIVER, linux-kernel
Hi all,
Recently I am learning the code related to Arm arch timer. I found that the
Cortex-A73 erratum 858921 does not set the corresponding callback functions:
set_next_event_phys and set_next_event_virt like other erratums. Won't it
get the wrong value when reading the counter during setting next event?
Looking forward to your reply.
Thanks,
Kunkun Jiang
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: A question about Cortex-A73 erratum 858921
2022-09-09 7:31 A question about Cortex-A73 erratum 858921 Kunkun Jiang
@ 2022-09-09 12:23 ` Marc Zyngier
2022-09-13 10:52 ` Kunkun Jiang
0 siblings, 1 reply; 3+ messages in thread
From: Marc Zyngier @ 2022-09-09 12:23 UTC (permalink / raw)
To: Kunkun Jiang
Cc: Mark Rutland, Daniel Lezcano, Thomas Gleixner, wanghaibin.wang,
Zenghui Yu, linux-arm-kernel, linux-kernel
On Fri, 09 Sep 2022 08:31:43 +0100,
Kunkun Jiang <jiangkunkun@huawei.com> wrote:
>
> Hi all,
>
> Recently I am learning the code related to Arm arch timer. I found that the
> Cortex-A73 erratum 858921 does not set the corresponding callback functions:
> set_next_event_phys and set_next_event_virt like other erratums. Won't it
> get the wrong value when reading the counter during setting next event?
Yup, you're correct.
This is a regression introduced by a38b71b0833e
("clocksource/drivers/arm_arch_timer: Move system register timer
programming over to CVAL"). We used to use the TVAL accessor which
doesn't need a read of the counter, while the switch to CVAL needs
one. Obviously, I didn't enough pay attention to the A73 erratum.
Please send in a fix for this.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: A question about Cortex-A73 erratum 858921
2022-09-09 12:23 ` Marc Zyngier
@ 2022-09-13 10:52 ` Kunkun Jiang
0 siblings, 0 replies; 3+ messages in thread
From: Kunkun Jiang @ 2022-09-13 10:52 UTC (permalink / raw)
To: Marc Zyngier
Cc: Mark Rutland, Daniel Lezcano, Thomas Gleixner, wanghaibin.wang,
Zenghui Yu, linux-arm-kernel, linux-kernel
Hi Marc,
Thank you for your reply, I've sent a fix.
https://lore.kernel.org/all/20220913104723.332-1-jiangkunkun@huawei.com/
Thanks,
Kunkun Jiang
On 2022/9/9 20:23, Marc Zyngier wrote:
> On Fri, 09 Sep 2022 08:31:43 +0100,
> Kunkun Jiang <jiangkunkun@huawei.com> wrote:
>> Hi all,
>>
>> Recently I am learning the code related to Arm arch timer. I found that the
>> Cortex-A73 erratum 858921 does not set the corresponding callback functions:
>> set_next_event_phys and set_next_event_virt like other erratums. Won't it
>> get the wrong value when reading the counter during setting next event?
> Yup, you're correct.
>
> This is a regression introduced by a38b71b0833e
> ("clocksource/drivers/arm_arch_timer: Move system register timer
> programming over to CVAL"). We used to use the TVAL accessor which
> doesn't need a read of the counter, while the switch to CVAL needs
> one. Obviously, I didn't enough pay attention to the A73 erratum.
>
> Please send in a fix for this.
>
> Thanks,
>
> M.
>
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 3+ messages in thread
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