From: ohaugan@codeaurora.org (Olav Haugan)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2] devicetree: Add generic IOMMU device tree bindings
Date: Thu, 10 Jul 2014 15:32:16 -0700 [thread overview]
Message-ID: <53BF1470.1000704@codeaurora.org> (raw)
In-Reply-To: <20140709105441.GE9485@arm.com>
On 7/9/2014 3:54 AM, Will Deacon wrote:
> On Wed, Jul 09, 2014 at 02:07:38AM +0100, Olav Haugan wrote:
>> On 6/30/2014 2:52 AM, Will Deacon wrote:
>>> On Fri, Jun 27, 2014 at 11:23:27PM +0100, Olav Haugan wrote:
>>>> Lets say I have an IOMMU with 2 masters and 2 SMRn slots with the
>>>> following stream IDs coming from the masters:
>>>>
>>>> Master 1: 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28
>>>> Master 2: 0x30
>>>>
>>>> To make this work I would program SMR[0] with StreamID 0x20 and mask 0xF
>>>> to ignore lower 4 bits. SMR[1] would just be StreamID 0x30 with mask 0x0.
>>>>
>>>> However, I could also have an IOMMU with 2 masters and 9 SMRn slots with
>>>> the following stream IDs:
>>>>
>>>> Master 1: 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28
>>>> Master 2: 0x29
>>>>
>>>> Here I would program all SMRn and leave the mask to be 0 for all SMRn's.
>>>> So how do I detect when to apply a mask or not?
>>>
>>> You would aim to use the smallest number of SMRs per master possible.
>>> You could probably use:
>>>
>>> Master 1: SMR[0].id == 0x20, SMR[0].mask = 0x07
>>> SMR[1].id == 0x28, SMR[1].mask = 0x00
>>>
>>> Master 2: SMR[2].id == 0x29, SMR[2].mask = 0x00
>>
>> So how does an algorithm figure this out in both my examples? The
>> algorithm would have to know about both (all) bus masters and their
>> stream IDs for a specific SMMU. If the algorithm operates on the set of
>> stream IDs for one bus master at a time the algorithm has no way of
>> knowing which bits can be ignored since it doesn't know the value of the
>> other stream IDs for the other bus masters and thus could potentially
>> create a mask that could cause a stream ID to match in two different
>> entries.
>
> Complete knowledge of the system topology (i.e. all bus masters) is a
> requirement for being able to configure the SMMU correctly if you want to
> guarantee that you don't have SMR aliasing issues.
So you agree that an algorithm needs to know about all the bus
masters/stream IDs for a specific IOMMU before it can figure out the
StreamID masks and how many SMRs can be allocated to a specific bus
master? Andreas's algorithm does not know about the other bus
masters/stream IDs. It operates on one bus master at a time.
>>>> I am not familiar with Andreas's proposal. Do you have a link?
>>>
>>> http://marc.info/?l=linux-arm-kernel&m=139110598005846&w=2
>>
>> Unless I am mistaken the algorithm works on one bus master at a time. I
>> don't think that will work.
>
> IIRC, it works for densely packed SIDs on the master, so it tries to build
> up power-of-2 sized groups for that master then mops up the rest with
> individual entries.
I ran the algorithm through a few trivial cases:
1)
Stream IDs: 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28
Number of SMRs: 9
In this case the algorithm decided to set mask to 0 for all entries
using up 8 of the SMRs.
2) Same Stream IDs but only 2 SMRs.
The algorithm gave an error saying I did not have enough SMRs.
Thanks,
Olav
--
The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation
next prev parent reply other threads:[~2014-07-10 22:32 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1400877218-4113-1-git-send-email-thierry.reding@gmail.com>
2014-05-30 13:16 ` [PATCH v2] devicetree: Add generic IOMMU device tree bindings Rob Herring
2014-05-30 19:06 ` Arnd Bergmann
2014-05-30 19:29 ` Hiroshi Doyu
2014-05-30 19:54 ` Arnd Bergmann
2014-06-01 9:55 ` Will Deacon
2014-06-04 13:39 ` Thierry Reding
2014-06-04 13:44 ` Thierry Reding
2014-06-04 13:53 ` Arnd Bergmann
2014-06-04 13:56 ` Will Deacon
2014-06-04 14:01 ` Arnd Bergmann
2014-06-04 16:39 ` Will Deacon
2014-05-30 19:31 ` Rob Herring
2014-05-30 19:49 ` Arnd Bergmann
2014-06-02 10:41 ` Dave Martin
2014-06-04 14:35 ` Thierry Reding
2014-06-04 16:41 ` Will Deacon
2014-06-04 21:00 ` Thierry Reding
2014-06-05 19:10 ` Varun Sethi
2014-06-16 15:27 ` Will Deacon
2014-06-16 16:56 ` Stuart Yoder
2014-06-16 17:04 ` Will Deacon
2014-06-16 17:30 ` Arnd Bergmann
2014-06-16 18:53 ` Stuart Yoder
2014-06-17 10:26 ` Varun Sethi
2014-06-17 10:43 ` Will Deacon
2014-06-17 11:21 ` Varun Sethi
2014-06-17 14:50 ` Stuart Yoder
2014-06-18 9:29 ` Will Deacon
2014-06-17 14:39 ` Stuart Yoder
2014-06-20 23:16 ` Olav Haugan
2014-06-24 9:18 ` Will Deacon
2014-06-24 17:57 ` Olav Haugan
2014-06-24 18:11 ` Will Deacon
2014-06-24 18:20 ` Arnd Bergmann
2014-06-25 9:17 ` Will Deacon
2014-06-25 9:27 ` Arnd Bergmann
2014-06-25 9:38 ` Will Deacon
2014-06-25 9:48 ` Arnd Bergmann
2014-06-25 9:57 ` Will Deacon
2014-06-25 10:12 ` Arnd Bergmann
2014-06-25 10:14 ` Will Deacon
2014-06-24 21:35 ` Olav Haugan
2014-06-25 9:18 ` Will Deacon
2014-06-27 22:23 ` Olav Haugan
2014-06-30 9:52 ` Will Deacon
2014-07-09 1:07 ` Olav Haugan
2014-07-09 10:54 ` Will Deacon
2014-07-10 22:32 ` Olav Haugan [this message]
2014-07-11 12:24 ` Will Deacon
[not found] <20140606224542.GA22188@mithrandir>
2014-06-07 13:22 ` Arnd Bergmann
2014-06-09 10:49 ` Thierry Reding
2014-05-23 20:36 Thierry Reding
2014-05-29 15:52 ` Stephen Warren
2014-05-30 7:30 ` Thierry Reding
2014-05-30 11:27 ` Dave Martin
2014-05-30 19:11 ` Arnd Bergmann
2014-06-02 10:56 ` Dave Martin
2014-06-04 21:12 ` Thierry Reding
2014-06-16 12:57 ` Will Deacon
2014-06-17 11:58 ` Thierry Reding
2014-06-17 12:18 ` Will Deacon
2014-06-17 23:37 ` Thierry Reding
2014-06-18 10:14 ` Will Deacon
2014-06-20 15:53 ` Arnd Bergmann
2014-06-20 17:50 ` Will Deacon
2014-06-20 18:55 ` Arnd Bergmann
2014-05-30 11:22 ` Dave Martin
2014-05-30 19:01 ` Arnd Bergmann
2014-06-02 11:44 ` Dave Martin
2014-06-04 21:32 ` Thierry Reding
2014-06-05 9:42 ` Arnd Bergmann
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=53BF1470.1000704@codeaurora.org \
--to=ohaugan@codeaurora.org \
--cc=linux-arm-kernel@lists.infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).