From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Paul Pawlowski <mrarmdev@gmail.com>, linux-mm@kvack.org
Subject: Re: Do DMA mappings get cleared on suspend?
Date: Tue, 20 Aug 2019 11:37:45 +0100 [thread overview]
Message-ID: <1566297465.2657.14.camel@HansenPartnership.com> (raw)
In-Reply-To: <CAKSqxP85cbYXt6q72aajXUTombZb-wbEfoWteBQrjJFO890rfg@mail.gmail.com>
On Mon, 2019-08-19 at 21:49 +0200, Paul Pawlowski wrote:
> Hello,
> Do DMA mappings get cleared when the device is suspended to RAM? A
> device I'm writing a driver for requires the DMA addresses not to
> change after a resume and trying to use DMA memory allocated before
> the suspend causes a device error. Is there a way to persist the
> mappings through a suspend?
What are you actually asking? The state of the IOMMU mappings should
be saved and restored on suspend/resume. However, whether mappings
that are inside actual PCI devices are saved and restored depends on
the actual device. In general we don't expect them to remember in-
flight I/O which is why I/O is quiesced before devices are suspended,
so the device should be inactive and any I/O in the upper layers will
be mapped on resume. The DMA addresses of the mailboxes are usually
saved and restored, but how is up to the driver.
James
next prev parent reply other threads:[~2019-08-20 10:38 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-19 19:49 Paul Pawlowski
2019-08-20 10:37 ` James Bottomley [this message]
2019-08-20 11:58 ` Paul Pawlowski
2019-08-20 15:58 ` Paul Pawlowski
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