linux-kernel - Re: [PATCH v2] arm: dma-mapping: Reset the device's dma

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Message-ID: <f625ecf5-45ac-95bb-6d3d-6d02f6658711@codeaurora.org>
Date:   Fri, 26 May 2017 20:25:12 +0530
From:   Sricharan R <sricharan@...eaurora.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     robin.murphy@....com, will.deacon@....com, joro@...tes.org,
        lorenzo.pieralisi@....com, iommu@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org, m.szyprowski@...sung.com,
        linux-kernel@...r.kernel.org, catalin.marinas@....com,
        linux-arch@...r.kernel.org, linux@...linux.org.uk
Subject: Re: [PATCH v2] arm: dma-mapping: Reset the device's dma_ops

Hi Laurent,

On 5/26/2017 7:44 PM, Laurent Pinchart wrote:
> Hi Sricharan,
> 
> Thank you for the patch.
> 
> On Friday 26 May 2017 16:13:37 Sricharan R wrote:
>> arch_teardown_dma_ops() being the inverse of arch_setup_dma_ops()
>> ,dma_ops should be cleared in the teardown path. Currently, only the
>> device's iommu mapping structures are cleared in arch_teardown_dma_ops,
>> but not the dma_ops. So on the next reprobe, dma_ops left in place is
>> stale from the first IOMMU setup, but iommu mappings has been disposed
>> of. This is a problem when the probe of the device is deferred and
>> recalled with the IOMMU probe deferral.
>>
>> So for fixing this, slightly refactor by moving the code from
>> __arm_iommu_detach_device to arm_iommu_detach_device and cleanup
>> the former. This takes care of resetting the dma_ops in the teardown
>> path.
>>
>> Signed-off-by: Sricharan R <sricharan@...eaurora.org>
>> Fixes: 09515ef5ddad ("of/acpi: Configure dma operations at probe time for
>> platform/amba/pci bus devices")
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> 
> Could you please push this upstream along with "[PATCH] ARM: dma-mapping: 
> Don't tear third-party mappings" ?
> 
> (And feel free to s/tear/tear down/ in the subject of that patch, I've only 
> noticed now that I forgot one word)

ok, will change the above and post it with the other patches.

Regards,
 Sricharan

> 
>> ---
>>  arch/arm/mm/dma-mapping.c | 25 ++++++++++---------------
>>  1 file changed, 10 insertions(+), 15 deletions(-)
>>
>> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
>> index c742dfd..6e82e87 100644
>> --- a/arch/arm/mm/dma-mapping.c
>> +++ b/arch/arm/mm/dma-mapping.c
>> @@ -2311,7 +2311,14 @@ int arm_iommu_attach_device(struct device *dev,
>>  }
>>  EXPORT_SYMBOL_GPL(arm_iommu_attach_device);
>>
>> -static void __arm_iommu_detach_device(struct device *dev)
>> +/**
>> + * arm_iommu_detach_device
>> + * @dev: valid struct device pointer
>> + *
>> + * Detaches the provided device from a previously attached map.
>> + * This voids the dma operations (dma_map_ops pointer)
>> + */
>> +void arm_iommu_detach_device(struct device *dev)
>>  {
>>  	struct dma_iommu_mapping *mapping;
>>
>> @@ -2324,22 +2331,10 @@ static void __arm_iommu_detach_device(struct device
>> *dev) iommu_detach_device(mapping->domain, dev);
>>  	kref_put(&mapping->kref, release_iommu_mapping);
>>  	to_dma_iommu_mapping(dev) = NULL;
>> +	set_dma_ops(dev, NULL);
>>
>>  	pr_debug("Detached IOMMU controller from %s device.\n", 
> dev_name(dev));
>>  }
>> -
>> -/**
>> - * arm_iommu_detach_device
>> - * @dev: valid struct device pointer
>> - *
>> - * Detaches the provided device from a previously attached map.
>> - * This voids the dma operations (dma_map_ops pointer)
>> - */
>> -void arm_iommu_detach_device(struct device *dev)
>> -{
>> -	__arm_iommu_detach_device(dev);
>> -	set_dma_ops(dev, NULL);
>> -}
>>  EXPORT_SYMBOL_GPL(arm_iommu_detach_device);
>>
>>  static const struct dma_map_ops *arm_get_iommu_dma_map_ops(bool coherent)
>> @@ -2379,7 +2374,7 @@ static void arm_teardown_iommu_dma_ops(struct device
>> *dev) if (!mapping)
>>  		return;
>>
>> -	__arm_iommu_detach_device(dev);
>> +	arm_iommu_detach_device(dev);
>>  	arm_iommu_release_mapping(mapping);
>>  }
> 

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