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Re: [Qemu-ppc] [Qemu-devel] [PATCH v2]booke: timer: Deactivate timer for
From: |
Alexander Graf |
Subject: |
Re: [Qemu-ppc] [Qemu-devel] [PATCH v2]booke: timer: Deactivate timer for target_bit above 61 |
Date: |
Mon, 10 Jun 2013 20:09:39 +0200 |
On 10.06.2013, at 19:20, Scott Wood wrote:
> On 06/10/2013 09:26:18 AM, Alexander Graf wrote:
>> On 06/10/2013 02:47 PM, Bhushan Bharat-R65777 wrote:
>>>> -----Original Message-----
>>>> From: Andreas Färber [mailto:address@hidden
>>>> Sent: Monday, June 10, 2013 5:43 PM
>>>> To: Bhushan Bharat-R65777
>>>> Cc: address@hidden; address@hidden; address@hidden; Wood Scott-
>>>> B07421; Bhushan Bharat-R65777
>>>> Subject: Re: [Qemu-devel] [PATCH v2]booke: timer: Deactivate timer for
>>>> target_bit above 61
>>>> So IIUC we can only allow 63 bits due to signedness, thus a maximum of
>>>> (1<< 62), thus target_bit<= 61.
>>>> Any chance at least the comment can be worded to explain that any better?
>>>> Maybe
>>>> also use (target-bit + 1>= 63) or period> INT64_MAX as condition?
>>> How about this:
>>> /* QEMU timer supports a maximum timer of INT64_MAX
>>> (0x7fffffff_ffffffff).
>>> * Run booke fit/wdog timer when
>>> * ((1ULL<< target_bit + 1)< 0x40000000_00000000), i.e target_bit =
>>> 61.
>>> * Also the time with this maximum target_bit (with current range of
>>> * CPU frequency PowerPC supports) will be many many years. So it is
>>> * pretty safe to stop the timer above this threshold. */
>> How about
>> /* This timeout will take years to trigger. Treat the timer as disabled. */
>
> There should be at least a brief mention that it's because the QEMU timer
> can't handle larger values,
If it can't handle higher values, maybe it's better to just set the timer value
to INT64_MAX when we detect an overflow? That would make the code plainly
obvious.
Alex
> with the detailed explanation in the changelog. A better lower bound on the
> number of years would be nice as well (e.g. "hundreds of years").
>
> -Scott
- [Qemu-ppc] [PATCH v2]booke: timer: Deactivate timer for target_bit above 61, Bharat Bhushan, 2013/06/10
- Re: [Qemu-ppc] [Qemu-devel] [PATCH v2]booke: timer: Deactivate timer for target_bit above 61, Peter Maydell, 2013/06/10
- Re: [Qemu-ppc] [Qemu-devel] [PATCH v2]booke: timer: Deactivate timer for target_bit above 61, Andreas Färber, 2013/06/10
- Re: [Qemu-ppc] [Qemu-devel] [PATCH v2]booke: timer: Deactivate timer for target_bit above 61, Bhushan Bharat-R65777, 2013/06/10
- Re: [Qemu-ppc] [Qemu-devel] [PATCH v2]booke: timer: Deactivate timer for target_bit above 61, Alexander Graf, 2013/06/10
- Re: [Qemu-ppc] [Qemu-devel] [PATCH v2]booke: timer: Deactivate timer for target_bit above 61, Scott Wood, 2013/06/10
- Re: [Qemu-ppc] [Qemu-devel] [PATCH v2]booke: timer: Deactivate timer for target_bit above 61,
Alexander Graf <=
- Re: [Qemu-ppc] [Qemu-devel] [PATCH v2]booke: timer: Deactivate timer for target_bit above 61, Bhushan Bharat-R65777, 2013/06/11
- Re: [Qemu-ppc] [Qemu-devel] [PATCH v2]booke: timer: Deactivate timer for target_bit above 61, Alexander Graf, 2013/06/11
- Re: [Qemu-ppc] [Qemu-devel] [PATCH v2]booke: timer: Deactivate timer for target_bit above 61, Bhushan Bharat-R65777, 2013/06/11
- Re: [Qemu-ppc] [Qemu-devel] [PATCH v2]booke: timer: Deactivate timer for target_bit above 61, Alexander Graf, 2013/06/11
- Re: [Qemu-ppc] [Qemu-devel] [PATCH v2]booke: timer: Deactivate timer for target_bit above 61, Bhushan Bharat-R65777, 2013/06/11
- Re: [Qemu-ppc] [Qemu-devel] [PATCH v2]booke: timer: Deactivate timer for target_bit above 61, Alexander Graf, 2013/06/11