From: Jon Masters <jcm@jonmasters.org>
To: "Robin Murphy" <robin.murphy@arm.com>,
"Niklas Söderlund" <niklas.soderlund+renesas@ragnatech.se>,
linux-arm-kernel@lists.infradead.org,
iommu@lists.linux-foundation.org, dmaengine@vger.kernel.org
Cc: linux-renesas-soc@vger.kernel.org, will.deacon@arm.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/2] Fix incorrect warning from dma-debug
Date: Sat, 6 May 2017 20:06:46 -0400 [thread overview]
Message-ID: <477ded30-eef2-3598-3a8d-95d206e11efb@jonmasters.org> (raw)
In-Reply-To: <57305FD8.7070006@arm.com>
On 05/09/2016 06:00 AM, Robin Murphy wrote:
> On 09/05/16 10:37, Robin Murphy wrote:
>> Hi Niklas,
>>
>> On 08/05/16 11:59, Niklas Söderlund wrote:
>>> Hi,
>>>
>>> While using CONFIG_DMA_API_DEBUG i came across this warning which I
>>> think is a false positive. As shown dma_sync_single_for_device() are
>>> called from the dma_map_single() call path. This triggers the warning
>>> since the dma-debug code have not yet been made aware of the mapping.
>>
>> Almost right ;) The thing being mapped (the SPI device's buffer) and the
>> thing being synced (the IOMMU's PTE) are entirely unrelated. Due to the
>> current of_iommu_init() setup, the IOMMU is probed long before
>> dma_debug_init() gets called, therefore DMA debug is missing entries for
>> some of the initial page table mappings and gets confused when we update
>> them later.
What was the eventual followup/fix for this? We're seeing similar traces
to this during internal testing of 4.11 kernels.
Jon.
--
Computer Architect
next prev parent reply other threads:[~2017-05-07 0:07 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-08 10:59 Niklas Söderlund
2016-05-08 10:59 ` [PATCH 1/2] dma-mapping: add __dma_sync_single_for_device() Niklas Söderlund
2016-05-08 10:59 ` [PATCH 2/2] iommu/io-pgtable-arm: use __dma_sync_single_for_device() Niklas Söderlund
2016-05-09 9:35 ` Will Deacon
2016-05-09 9:37 ` [PATCH 0/2] Fix incorrect warning from dma-debug Robin Murphy
2016-05-09 10:00 ` Robin Murphy
2017-05-07 0:06 ` Jon Masters [this message]
2017-05-08 9:19 ` Geert Uytterhoeven
2017-05-08 9:39 ` Robin Murphy
2017-01-25 16:23 ` Geert Uytterhoeven
2017-01-25 17:27 ` Robin Murphy
2017-01-25 20:32 ` Geert Uytterhoeven
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