Re: [PATCH v4 09/15] drivers: acpi: iort: add support for ARM SMMU platform devices creation

[Dennis Chen]

Hi Lorenzo,

On Mon, Aug 15, 2016 at 04:23:34PM +0100, Lorenzo Pieralisi wrote:
> In ARM ACPI systems, IOMMU components are specified through static
> IORT table entries. In order to create platform devices for the
> corresponding ARM SMMU components, IORT kernel code should be made
> able to parse IORT table entries and create platform devices
> dynamically.
> 
> This patch adds the generic IORT infrastructure required to create
> platform devices for ARM SMMUs.
> 
> ARM SMMU versions have different resources requirement therefore this
> patch also introduces an IORT specific structure (ie iort_iommu_config)
> that contains hooks (to be defined when the corresponding ARM SMMU
> driver support is added to the kernel) to be used to define the
> platform devices names, init the IOMMUs, count their resources and
> finally initialize them.
> 
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> Cc: Hanjun Guo <hanjun.guo@xxxxxxxxxx>
> Cc: Tomasz Nowicki <tn@xxxxxxxxxxxx>
> Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
> ---
>  drivers/acpi/arm64/iort.c | 153 ++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 153 insertions(+)
> 
> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> index f6db3d8..4043071 100644
> --- a/drivers/acpi/arm64/iort.c
> +++ b/drivers/acpi/arm64/iort.c
> @@ -22,6 +22,7 @@
>  #include <linux/kernel.h>
>  #include <linux/list.h>
>  #include <linux/pci.h>
> +#include <linux/platform_device.h>
>  #include <linux/slab.h>
>  
>  struct iort_its_msi_chip {
> @@ -454,6 +455,157 @@ iort_get_device_domain(struct device *dev, u32 req_id)
>  	return irq_find_matching_fwnode(handle, DOMAIN_BUS_PCI_MSI);
>  }
>  
> +struct iort_iommu_config {
> +	const char *name;
> +	int (*iommu_init)(struct acpi_iort_node *node);
> +	bool (*iommu_is_coherent)(struct acpi_iort_node *node);
> +	int (*iommu_count_resources)(struct acpi_iort_node *node);
> +	void (*iommu_init_resources)(struct resource *res,
> +				     struct acpi_iort_node *node);
> +};
> +
> +static const struct iort_iommu_config * __init
> +iort_get_iommu_config(struct acpi_iort_node *node)
> +{
> +	return NULL;
> +}
> +
> +/**
> + * iort_add_smmu_platform_device() - Allocate a platform device for SMMU
> + * @fwnode: IORT node associated fwnode handle
> + * @node: Pointer to SMMU ACPI IORT node
> + *
> + * Returns: 0 on success, <0 failure
> + */
> +static int __init
> +iort_add_smmu_platform_device(struct fwnode_handle *fwnode,
> +			      struct acpi_iort_node *node)
> +{
> +	struct platform_device *pdev;
> +	struct resource *r;
> +	enum dev_dma_attr attr;
> +	int ret, count;
> +	const struct iort_iommu_config *ops =
> +				iort_get_iommu_config(node);
> +
> +	if (!ops)
> +		return -ENODEV;
> +
> +	pdev = platform_device_alloc(ops->name, PLATFORM_DEVID_AUTO);
> +	if (!pdev)
> +		return PTR_ERR(pdev);
> +
> +	count = ops->iommu_count_resources(node);
> +
> +	r = kcalloc(count, sizeof(*r), GFP_KERNEL);
> +	if (!r) {
> +		ret = -ENOMEM;
> +		goto dev_put;
> +	}
> +
> +	ops->iommu_init_resources(r, node);
> +
> +	ret = platform_device_add_resources(pdev, r, count);
> +	/*
> +	 * Resources are duplicated in platform_device_add_resources,
> +	 * free their allocated memory
> +	 */
> +	kfree(r);
> +
> +	if (ret)
> +		goto dev_put;
> +
> +	/*
> +	 * Add a copy of IORT node pointer to platform_data to
> +	 * be used to retrieve IORT data information.
> +	 */
> +	ret = platform_device_add_data(pdev, &node, sizeof(node));
> +	if (ret)
> +		goto dev_put;
> +
> +	pdev->dev.dma_mask = kmalloc(sizeof(*pdev->dev.dma_mask), GFP_KERNEL);
> +	if (!pdev->dev.dma_mask) {
> +		ret = -ENOMEM;
> +		goto dev_put;
> +	}
> +
> +	pdev->dev.fwnode = fwnode;
> +
> +	/*
> +	 * Set default dma mask value for the table walker,
> +	 * to be overridden on probing with correct value.
> +	 */
> +	*pdev->dev.dma_mask = DMA_BIT_MASK(32);
> +	pdev->dev.coherent_dma_mask = *pdev->dev.dma_mask;
> +
> +	attr = ops->iommu_is_coherent(node) ?
> +			     DEV_DMA_COHERENT : DEV_DMA_NON_COHERENT;
> +
> +	/* Configure DMA for the page table walker */
> +	acpi_dma_configure(&pdev->dev, attr);
> +
> +	ret = platform_device_add(pdev);
> +	if (ret)
> +		goto dma_deconfigure;
> +
> +	return 0;
> +
> +dma_deconfigure:
> +	acpi_dma_deconfigure(&pdev->dev);
> +	kfree(pdev->dev.dma_mask);
> +
> +dev_put:
> +	platform_device_put(pdev);
> +
> +	return ret;
> +}
> +
> +static void __init iort_smmu_init(void)
> +{
> +	struct acpi_iort_node *iort_node, *iort_end;
> +	struct acpi_table_iort *iort;
> +	struct fwnode_handle *fwnode;
> +	int i, ret;
> +
> +	/*
> +	 * table and iort will both point to the start of IORT table, but
> +	 * have different struct types
> +	 */
> +	iort = (struct acpi_table_iort *)iort_table;
>
If the firmware of a platform happens to miss the IORT table, then iort_table here
will be a NULL pointer, in this case 'NULL pointer dereference' kernel panic will occur, 
if this is not an expected behavior then we can add a sanity check here to avoid this. 
IORT missing is a fatal error? I don't think so.

Thanks,
Dennis
> +
> +	/* Get the first IORT node */
> +	iort_node = ACPI_ADD_PTR(struct acpi_iort_node, iort_table,
> +				 iort->node_offset);
> +	iort_end = ACPI_ADD_PTR(struct acpi_iort_node, iort_table,
> +				iort_table->length);
> +
> +	for (i = 0; i < iort->node_count; i++) {
> +
> +		if (iort_node >= iort_end) {
> +			pr_err("iort node pointer overflows, bad table\n");
> +			return;
> +		}
> +
> +		if (iort_node->type == ACPI_IORT_NODE_SMMU ||
> +		    iort_node->type == ACPI_IORT_NODE_SMMU_V3) {
> +			fwnode = iort_get_fwnode(iort_node);
> +
> +			if (!fwnode)
> +				continue;
> +
> +			ret = iort_add_smmu_platform_device(fwnode,
> +							    iort_node);
> +			if (ret) {
> +				pr_err("Error in platform device creation\n");
> +				return;
> +			}
> +		}
> +
> +		iort_node = ACPI_ADD_PTR(struct acpi_iort_node, iort_node,
> +					 iort_node->length);
> +	}
> +}
> +
>  void __init iort_table_detect(void)
>  {
>  	acpi_status status;
> @@ -465,4 +617,5 @@ void __init iort_table_detect(void)
>  	}
>  
>  	acpi_probe_device_table(iort);
> +	iort_smmu_init();
>  }
> -- 
> 2.6.4
>