From: tchalamarla@caviumnetworks•com (Tirumalesh Chalamarla)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH V2] iommu/arm-smmu-v2: Workaround for ThunderX errata#27704
Date: Wed, 24 Feb 2016 11:15:23 -0800 [thread overview]
Message-ID: <56CE014B.3080400@caviumnetworks.com> (raw)
In-Reply-To: <20160224190628.GA9003@leverpostej>
On 02/24/2016 11:10 AM, Mark Rutland wrote:
> On Wed, Feb 24, 2016 at 03:54:48PM +0000, Chalamarla, Tirumalesh wrote:
>>
>> On 2/24/16, 3:32 AM, "Mark Rutland" <mark.rutland@arm•com> wrote:
>>
>>> On Tue, Feb 23, 2016 at 03:50:21PM -0800, Tirumalesh Chalamarla wrote:
>>>> in Summary,
>>>>
>>>> if i change asid-base to cavium,asid-base and still use DT for
>>>> supplying base value, is this a solution that will be accepted,
>>>
>>> No. The property is _insufficient_, regardless of its name. This has
>>> been pointed out more than once.
>>>
>>> A base alone does not tell you what set of IDs it is valid to use
>>> without risking a clash. The OS is well within its rights to allocate
>>> _any_ ID above that base. It is not a requirement of the hardware nor
>>> the binding that the OS allocate a contiguous set of IDs starting at the
>>> base.
>>>
>>> Consider:
>>>
>>> smmu_a {
>>> whatver,*id-base = <128>;
>>> };
>>>
>>> smmu_b {
>>> whatever,*id-base = <64>;
>>> };
>>>
>>> In both cases, the *IDs 129+ could be allocated on both SMMUs.
>>
>> Does adding a check to see if base + number of contexts supported will not overlap with each other
>> Make it acceptable.
>> Or do you want the size be provided from DT also?
>
> At this point I think Robin's suggestion of giving the ThunderX SMMU a
> different compatible string and treating that as a separate case
> entirely is the best thing to do.
>
> Then the only requirement is that _all_ the ThunderX SMMUs with shared
> TLBs are under the control of the OS, and it can allocate IDs as it
> chooses, so long as it ensures that there are no conflicts across all
> the SMMUs it is in control of.
>
yes, resending based on the suggestions.
> Mark.
>
next prev parent reply other threads:[~2016-02-24 19:15 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-18 18:29 [PATCH V2] iommu/arm-smmu-v2: Workaround for ThunderX errata#27704 tchalamarla at caviumnetworks.com
2016-02-23 11:49 ` Will Deacon
2016-02-23 12:19 ` Robin Murphy
2016-02-23 23:56 ` Tirumalesh Chalamarla
2016-02-24 13:38 ` Robin Murphy
2016-02-24 18:53 ` Tirumalesh Chalamarla
2016-02-23 12:26 ` Mark Rutland
2016-02-23 23:50 ` Tirumalesh Chalamarla
2016-02-24 11:32 ` Mark Rutland
2016-02-24 15:54 ` Chalamarla, Tirumalesh
2016-02-24 19:10 ` Mark Rutland
2016-02-24 19:15 ` Tirumalesh Chalamarla [this message]
2016-02-23 23:54 ` Tirumalesh Chalamarla
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