From: m.szyprowski@samsung•com (Marek Szyprowski)
To: linux-arm-kernel@lists•infradead.org
Subject: Cache maintenance in arm_iommu_alloc_attrs for iommu_coherent_ops
Date: Thu, 22 May 2014 10:30:16 +0200 [thread overview]
Message-ID: <537DB598.9080300@samsung.com> (raw)
In-Reply-To: <CAD15agav14RUb473+iCm24HM9eQfWYG8ytZOfpzm5j0e3EX3WQ@mail.gmail.com>
Hello,
On 2014-05-21 10:52, Ritesh Harjani wrote:
> Hi All,
>
> There is this path in arm dma-mapping.c with respect to iommu coherent
> buffer allocation:
>
> 1. arm_iommu_alloc_attrs
> -> __iommu_alloc_buffer
> -> __dma_clear_buffer
>
>
> __dma_clear_buffer zeros out the allocated pages but also flushes the
> cpu and the outer cache for coherent iommu ops.
>
> I think the above operation for coherent iommu ops should not include
> cache flush operation right ??
> Or I am missing something here ? Whether this is put intentional or
> its a mistake we can correct ?
You are right. For coherent devices we can skip cache maintenance after
clearing the buffer. I think that the above mentioned code flow has been
overlooked when coherent iommu support has been added.
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
prev parent reply other threads:[~2014-05-22 8:30 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-21 8:52 Cache maintenance in arm_iommu_alloc_attrs for iommu_coherent_ops Ritesh Harjani
2014-05-21 9:37 ` Ritesh Harjani
2014-05-22 8:31 ` Marek Szyprowski
2014-05-22 15:52 ` Ritesh Harjani
2014-05-22 8:30 ` Marek Szyprowski [this message]
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=537DB598.9080300@samsung.com \
--to=m.szyprowski@samsung$(echo .)com \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
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