From: grygorii.strashko@ti•com (Grygorii Strashko)
To: linux-arm-kernel@lists•infradead.org
Subject: [RFC PATCH v2 2/7] dma-mapping: replace set_arch_dma_coherent_ops with arch_setup_dma_ops
Date: Tue, 9 Sep 2014 17:15:58 +0300 [thread overview]
Message-ID: <540F0B9E.5060505@ti.com> (raw)
In-Reply-To: <20140908103129.GC26030@arm.com>
Hi Will,
On 09/08/2014 01:31 PM, Will Deacon wrote:
> On Fri, Sep 05, 2014 at 04:37:41PM +0100, Grygorii Strashko wrote:
>
>> On 09/02/2014 08:56 PM, Will Deacon wrote:
>>> set_arch_dma_coherent_ops is called from of_dma_configure in order to
>>> swizzle the architectural dma-mapping functions over to a cache-coherent
>>> implementation. This is currently implemented only for ARM.
>>>
>>> In anticipation of re-using this mechanism for IOMMU-backed dma-mapping
>>> ops too, this patch replaces the function with a broader
>>> arch_setup_dma_ops callback which is also responsible for setting the
>>> DMA mask and offset as well as selecting the correct mapping functions.
>>>
>>> A further advantage of this split is that it nicely isolates the
>>> of-specific code from the dma-mapping code, allowing potential reuse by
>>> other buses (e.g. PCI) in the future.
>>
>> I think this patch can introduce a regression if it will be used as is :(
>>
>> When this code was initially created there ware a lot of discussion about
>> and finally it was decided to configure all common (for all arches) DMA
>> specific parameters for devices in common code, while strictly arch
>> specific things using arch specific APIs/callbacks.
>>
>> The following parameters are common now:
>> dev->coherent_dma_mask = mask;
>> dev->dma_mask = &dev->coherent_dma_mask;
>> dev->dma_pfn_offset = offset;
>>
>> and they need to be set always, otherwise it will affect on other
>> DT-based arches.
>
> Ok, in which case we can either configure the struct device in
> of_dma_configure before calling arch_setup_dma_ops, or we can do the work
> in a generic version of arch_setup_dma_ops (that I haven't added yet).
Just think that it would more simpler to add arch-API:
arch_setup_iommu(struct device *dev, struct iommu_dma_mapping *iommu)
and call it at the end of of_dma_configure() as following:
arch_setup_iommu(dev, of_iommu_configure(dev));
so it will setup IOMMU parameters for device and overwrite DMA
parameters respectively.
if IOMMU is not present/disabled arch_setup_iommu() will be a NOP and
system will roll back to default (old) behavior.
Also it will simplify ARM dma-mapping changes -
only IOMMU code will need to be added.
Best regards,
-grygorii
next prev parent reply other threads:[~2014-09-09 14:15 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-02 17:56 [RFC PATCH v2 0/7] Introduce automatic DMA configuration for IOMMU masters Will Deacon
2014-09-02 17:56 ` [RFC PATCH v2 1/7] iommu: provide early initialisation hook for IOMMU drivers Will Deacon
2014-09-10 11:29 ` Marek Szyprowski
2014-09-02 17:56 ` [RFC PATCH v2 2/7] dma-mapping: replace set_arch_dma_coherent_ops with arch_setup_dma_ops Will Deacon
2014-09-05 15:37 ` Grygorii Strashko
2014-09-08 10:31 ` Will Deacon
2014-09-09 14:15 ` Grygorii Strashko [this message]
2014-09-02 17:56 ` [RFC PATCH v2 3/7] iommu: add new iommu_ops callback for adding an OF device Will Deacon
2014-09-10 11:16 ` Marek Szyprowski
2014-09-10 11:22 ` Will Deacon
2014-09-10 11:33 ` Will Deacon
2014-09-02 17:56 ` [RFC PATCH v2 4/7] iommu: provide helper function to configure an IOMMU for an of master Will Deacon
2014-09-02 19:10 ` Arnd Bergmann
2014-09-04 11:26 ` Will Deacon
2014-09-04 11:59 ` Arnd Bergmann
2014-09-04 12:28 ` Will Deacon
2014-09-10 13:01 ` Laurent Pinchart
2014-09-10 13:06 ` Will Deacon
2014-09-02 17:56 ` [RFC PATCH v2 5/7] dma-mapping: detect and configure IOMMU in of_dma_configure Will Deacon
2014-09-02 17:56 ` [RFC PATCH v2 6/7] arm: call iommu_init before of_platform_populate Will Deacon
2014-09-02 18:13 ` Arnd Bergmann
2014-09-02 17:56 ` [RFC PATCH v2 7/7] arm: dma-mapping: plumb our iommu mapping ops into arch_setup_dma_ops Will Deacon
2014-09-02 18:14 ` Arnd Bergmann
2014-09-02 19:11 ` [RFC PATCH v2 0/7] Introduce automatic DMA configuration for IOMMU masters Arnd Bergmann
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