From: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
To: Varun Sethi <Varun.Sethi-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
Cc: Mark.Rutland-5wv7dgnIgG8@public.gmane.org,
devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org,
will.deacon-5wv7dgnIgG8@public.gmane.org,
stuart.yoder-KZfg59tc24xl57MIdRCFDg@public.gmane.org,
robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org,
iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org,
thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org,
linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
Subject: Re: [RFC][PATCH] devicetree: Add master-id-bits property to the iommu device
Date: Mon, 15 Sep 2014 04:38:29 +0200 [thread overview]
Message-ID: <201409150438.29649.arnd@arndb.de> (raw)
In-Reply-To: <1410718646-9710-1-git-send-email-Varun.Sethi-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
On Sunday 14 September 2014, Varun Sethi wrote:
> "master-id-bits" property added to the IOMMU device node. This property can
> be used by the IOMMU driver to match relevan bits in the master id expressed
> by a DMA master.
>
> This can be used to mask out certain bits that get added to the device master id
> due to IOMMU topology. For example, in case of MMU-500 the TBUID gets appended to
> the master id. This prevents sharing of a stream ID, amongst devices which are
> connected to different TBUs.
>
> Signed-off-by: Varun Sethi <Varun.Sethi-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
This seems rather specific to MMU-500. I don't think that most IOMMUs would
use the term 'master ID', 'stream ID' or even the general concept, and you don't
expand the acronym 'TBU'. I've seen many IOMMUs and I don't even know what
that means.
Why do you think this is something that is needed to be known at the global
level, rather than a property for some individual drivers?
Arnd
WARNING: multiple messages have this Message-ID (diff)
From: arnd@arndb.de (Arnd Bergmann)
To: linux-arm-kernel@lists.infradead.org
Subject: [RFC][PATCH] devicetree: Add master-id-bits property to the iommu device
Date: Mon, 15 Sep 2014 04:38:29 +0200 [thread overview]
Message-ID: <201409150438.29649.arnd@arndb.de> (raw)
In-Reply-To: <1410718646-9710-1-git-send-email-Varun.Sethi@freescale.com>
On Sunday 14 September 2014, Varun Sethi wrote:
> "master-id-bits" property added to the IOMMU device node. This property can
> be used by the IOMMU driver to match relevan bits in the master id expressed
> by a DMA master.
>
> This can be used to mask out certain bits that get added to the device master id
> due to IOMMU topology. For example, in case of MMU-500 the TBUID gets appended to
> the master id. This prevents sharing of a stream ID, amongst devices which are
> connected to different TBUs.
>
> Signed-off-by: Varun Sethi <Varun.Sethi@freescale.com>
This seems rather specific to MMU-500. I don't think that most IOMMUs would
use the term 'master ID', 'stream ID' or even the general concept, and you don't
expand the acronym 'TBU'. I've seen many IOMMUs and I don't even know what
that means.
Why do you think this is something that is needed to be known at the global
level, rather than a property for some individual drivers?
Arnd
next prev parent reply other threads:[~2014-09-15 2:38 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-14 18:17 [RFC][PATCH] devicetree: Add master-id-bits property to the iommu device Varun Sethi
2014-09-14 18:17 ` Varun Sethi
[not found] ` <1410718646-9710-1-git-send-email-Varun.Sethi-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
2014-09-15 2:38 ` Arnd Bergmann [this message]
2014-09-15 2:38 ` Arnd Bergmann
[not found] ` <201409150438.29649.arnd-r2nGTMty4D4@public.gmane.org>
2014-09-15 10:37 ` Varun Sethi
2014-09-15 10:37 ` Varun Sethi
[not found] ` <bfdff6494d7f46ab9a9f00f94159e9e1-AZ66ij2kwaacCcN9WK45f+O6mTEJWrR4XA4E9RH9d+qIuWR1G4zioA@public.gmane.org>
2014-09-15 16:57 ` Arnd Bergmann
2014-09-15 16:57 ` Arnd Bergmann
[not found] ` <201409151857.05463.arnd-r2nGTMty4D4@public.gmane.org>
2014-09-16 18:04 ` Varun Sethi
2014-09-16 18:04 ` Varun Sethi
[not found] ` <febe4a288f2f438ca95988929ee71580-AZ66ij2kwaacCcN9WK45f+O6mTEJWrR4XA4E9RH9d+qIuWR1G4zioA@public.gmane.org>
2014-09-22 9:23 ` Thierry Reding
2014-09-22 9:23 ` Thierry Reding
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