From: laurent.pinchart@ideasonboard.com (Laurent Pinchart)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 4/8] of: dma: Split of_configure_dma() into mask and ops configuration
Date: Fri, 12 Aug 2016 18:18:04 +0300 [thread overview]
Message-ID: <1651151.fes0RShRSW@avalon> (raw)
In-Reply-To: <CAAFQd5BkpHrF=2=UXFA2mPKe0VQAD3J_XSNrZYHP0br5hw=Gsw@mail.gmail.com>
Hi Tomasz,
On Friday 12 Aug 2016 16:31:47 Tomasz Figa wrote:
> On Tue, Aug 9, 2016 at 7:49 AM, Sricharan R wrote:
> > From: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> >
> > The of_configure_dma() function configures both the DMA masks and ops.
> > Moving DMA ops configuration to probe time would thus also delay
> > configuration of the DMA masks, which might not be safe. To avoid issues
>
> Do we know any example cases when it might be unsafe? I think we kind
> of rely on the fact that DMA mapping (and so DMA masks as well) is not
> used before probing the device anyway, because we let the IOMMU
> attachment happen at probe time, which essentially makes any earlier
> attempts to use DMA mapping on such device incorrect.
I don't know of any such situation, but (if I remember correctly) when I
discussed the IOMMU rework with Arnd Bergman and Will Deacon there was a
concern that someone, somewhere was relying on the mask being set early.
I personally would like to drop this patch, but it might be difficult to
ensure this wouldn't cause a regression. There should certainly be no DMA
mapping created before IOMMU attachment, but the DMA mask could possibly be
used somewhere else.
--
Regards,
Laurent Pinchart
next prev parent reply other threads:[~2016-08-12 15:18 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-08 22:49 [PATCH 0/8] IOMMU Probe deferral support Sricharan R
2016-08-08 22:49 ` [PATCH 1/8] arm: dma-mapping: Don't override dma_ops in arch_setup_dma_ops() Sricharan R
2016-09-02 8:16 ` Marek Szyprowski
2016-09-07 6:24 ` Sricharan
2016-08-08 22:49 ` [PATCH 2/8] of: dma: Move range size workaround to of_dma_get_range() Sricharan R
2016-08-08 22:49 ` [PATCH 3/8] of: dma: Make of_dma_deconfigure() public Sricharan R
2016-08-08 22:49 ` [PATCH 4/8] of: dma: Split of_configure_dma() into mask and ops configuration Sricharan R
2016-08-12 7:31 ` Tomasz Figa
2016-08-12 15:18 ` Laurent Pinchart [this message]
2016-08-12 15:45 ` Sricharan
2016-09-09 6:53 ` Magnus Damm
2016-09-09 9:48 ` Sricharan
2016-08-08 22:49 ` [PATCH 5/8] drivers: platform: Configure dma operations at probe time Sricharan R
2016-08-16 9:25 ` Laurent Pinchart
2016-08-16 12:28 ` Sricharan
2016-08-08 22:49 ` [PATCH 6/8] drivers: platform: Remove call to of_dma_(con/decon)figure_ops Sricharan R
2016-08-12 7:33 ` Tomasz Figa
2016-08-12 15:42 ` Sricharan
2016-08-08 22:49 ` [PATCH 7/8] iommu: of: Handle IOMMU lookup failure with deferred probing or error Sricharan R
2016-08-12 7:46 ` Tomasz Figa
2016-08-12 15:40 ` Sricharan
2016-09-02 8:09 ` Marek Szyprowski
2016-09-07 6:16 ` Sricharan
2016-09-02 12:52 ` Marek Szyprowski
2016-09-07 6:29 ` Sricharan
2016-08-08 22:49 ` [PATCH 8/8] drivers: iommu: arm-smmu: Set iommu_ops in probe Sricharan R
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