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Date:   Tue, 4 Apr 2017 12:31:58 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Sricharan R <sricharan@...eaurora.org>, 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,
        bhelgaas@...gle.com, linux-pci@...r.kernel.org,
        linux-acpi@...r.kernel.org, tn@...ihalf.com, hanjun.guo@...aro.org,
        okaya@...eaurora.org, robh+dt@...nel.org, frowand.list@...il.com,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        sudeep.holla@....com, rjw@...ysocki.net, lenb@...nel.org,
        catalin.marinas@....com, arnd@...db.de, linux-arch@...r.kernel.org,
        gregkh@...uxfoundation.org
Subject: Re: [PATCH V10 09/12] drivers: acpi: Handle IOMMU lookup failure with
 deferred probing or error

On 04/04/17 11:18, Sricharan R wrote:
> This is an equivalent to the DT's handling of the iommu master's probe
> with deferred probing when the corrsponding iommu is not probed yet.
> The lack of a registered IOMMU can be caused by the lack of a driver for
> the IOMMU, the IOMMU device probe not having been performed yet, having
> been deferred, or having failed.
> 
> The first case occurs when the firmware describes the bus master and
> IOMMU topology correctly but no device driver exists for the IOMMU yet
> or the device driver has not been compiled in. Return NULL, the caller
> will configure the device without an IOMMU.
> 
> The second and third cases are handled by deferring the probe of the bus
> master device which will eventually get reprobed after the IOMMU.
> 
> The last case is currently handled by deferring the probe of the bus
> master device as well. A mechanism to either configure the bus master
> device without an IOMMU or to fail the bus master device probe depending
> on whether the IOMMU is optional or mandatory would be a good
> enhancement.

I think we really have caught everything now...

Reviewed-by: Robin Murphy <robin.murphy@....com>

> Tested-by: Hanjun Guo <hanjun.guo@...aro.org>
> [Lorenzo: Added fixes for dma_coherent_mask overflow, acpi_dma_configure
>           called multiple times for same device]
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
> Signed-off-by: Sricharan R <sricharan@...eaurora.org>
> ---
> 
>  [V10] Added Lorenzo's ACPI fix for coherent_dma_mask overflow
>        and the fix for dma_configure getting called more than
>        once for the same device.
> 
>  drivers/acpi/arm64/iort.c  | 33 ++++++++++++++++++++++++++++++++-
>  drivers/acpi/scan.c        | 11 ++++++++---
>  drivers/base/dma-mapping.c |  2 +-
>  include/acpi/acpi_bus.h    |  2 +-
>  include/linux/acpi.h       |  7 +++++--
>  5 files changed, 47 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> index 3dd9ec3..e323ece 100644
> --- a/drivers/acpi/arm64/iort.c
> +++ b/drivers/acpi/arm64/iort.c
> @@ -543,6 +543,14 @@ static const struct iommu_ops *iort_iommu_xlate(struct device *dev,
>  	const struct iommu_ops *ops = NULL;
>  	int ret = -ENODEV;
>  	struct fwnode_handle *iort_fwnode;
> +	struct iommu_fwspec *fwspec = dev->iommu_fwspec;
> +
> +	/*
> +	 * If we already translated the fwspec there
> +	 * is nothing left to do, return the iommu_ops.
> +	 */
> +	if (fwspec && fwspec->ops)
> +		return fwspec->ops;
>  
>  	if (node) {
>  		iort_fwnode = iort_get_fwnode(node);
> @@ -550,8 +558,17 @@ static const struct iommu_ops *iort_iommu_xlate(struct device *dev,
>  			return NULL;
>  
>  		ops = iommu_ops_from_fwnode(iort_fwnode);
> +		/*
> +		 * If the ops look-up fails, this means that either
> +		 * the SMMU drivers have not been probed yet or that
> +		 * the SMMU drivers are not built in the kernel;
> +		 * Depending on whether the SMMU drivers are built-in
> +		 * in the kernel or not, defer the IOMMU configuration
> +		 * or just abort it.
> +		 */
>  		if (!ops)
> -			return NULL;
> +			return iort_iommu_driver_enabled(node->type) ?
> +			       ERR_PTR(-EPROBE_DEFER) : NULL;
>  
>  		ret = arm_smmu_iort_xlate(dev, streamid, iort_fwnode, ops);
>  	}
> @@ -625,12 +642,26 @@ const struct iommu_ops *iort_iommu_configure(struct device *dev)
>  
>  		while (parent) {
>  			ops = iort_iommu_xlate(dev, parent, streamid);
> +			if (IS_ERR_OR_NULL(ops))
> +				return ops;
>  
>  			parent = iort_node_get_id(node, &streamid,
>  						  IORT_IOMMU_TYPE, i++);
>  		}
>  	}
>  
> +	/*
> +	 * If we have reason to believe the IOMMU driver missed the initial
> +	 * add_device callback for dev, replay it to get things in order.
> +	 */
> +	if (!IS_ERR_OR_NULL(ops) && ops->add_device &&
> +	    dev->bus && !dev->iommu_group) {
> +		int err = ops->add_device(dev);
> +
> +		if (err)
> +			ops = ERR_PTR(err);
> +	}
> +
>  	return ops;
>  }
>  
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index 1926918..2a513cc 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -1373,20 +1373,25 @@ enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev)
>   * @dev: The pointer to the device
>   * @attr: device dma attributes
>   */
> -void acpi_dma_configure(struct device *dev, enum dev_dma_attr attr)
> +int acpi_dma_configure(struct device *dev, enum dev_dma_attr attr)
>  {
>  	const struct iommu_ops *iommu;
> +	u64 size;
>  
>  	iort_set_dma_mask(dev);
>  
>  	iommu = iort_iommu_configure(dev);
> +	if (IS_ERR(iommu))
> +		return PTR_ERR(iommu);
>  
> +	size = max(dev->coherent_dma_mask, dev->coherent_dma_mask + 1);
>  	/*
>  	 * Assume dma valid range starts at 0 and covers the whole
>  	 * coherent_dma_mask.
>  	 */
> -	arch_setup_dma_ops(dev, 0, dev->coherent_dma_mask + 1, iommu,
> -			   attr == DEV_DMA_COHERENT);
> +	arch_setup_dma_ops(dev, 0, size, iommu, attr == DEV_DMA_COHERENT);
> +
> +	return 0;
>  }
>  EXPORT_SYMBOL_GPL(acpi_dma_configure);
>  
> diff --git a/drivers/base/dma-mapping.c b/drivers/base/dma-mapping.c
> index 82bd45c..755a2b5 100644
> --- a/drivers/base/dma-mapping.c
> +++ b/drivers/base/dma-mapping.c
> @@ -368,7 +368,7 @@ int dma_configure(struct device *dev)
>  	} else if (has_acpi_companion(dma_dev)) {
>  		attr = acpi_get_dma_attr(to_acpi_device_node(dma_dev->fwnode));
>  		if (attr != DEV_DMA_NOT_SUPPORTED)
> -			acpi_dma_configure(dev, attr);
> +			ret = acpi_dma_configure(dev, attr);
>  	}
>  
>  	if (bridge)
> diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
> index ef0ae8a..2a9a5de 100644
> --- a/include/acpi/acpi_bus.h
> +++ b/include/acpi/acpi_bus.h
> @@ -575,7 +575,7 @@ struct acpi_pci_root {
>  
>  bool acpi_dma_supported(struct acpi_device *adev);
>  enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev);
> -void acpi_dma_configure(struct device *dev, enum dev_dma_attr attr);
> +int acpi_dma_configure(struct device *dev, enum dev_dma_attr attr);
>  void acpi_dma_deconfigure(struct device *dev);
>  
>  struct acpi_device *acpi_find_child_device(struct acpi_device *parent,
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index 9b05886..79d06ef6 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -762,8 +762,11 @@ static inline enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev)
>  	return DEV_DMA_NOT_SUPPORTED;
>  }
>  
> -static inline void acpi_dma_configure(struct device *dev,
> -				      enum dev_dma_attr attr) { }
> +static inline int acpi_dma_configure(struct device *dev,
> +				     enum dev_dma_attr attr)
> +{
> +	return 0;
> +}
>  
>  static inline void acpi_dma_deconfigure(struct device *dev) { }
>  
> 

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