Subject: Re: [PATCH 4/7 v2] pseries/iommu: implement DDW-aware dma_get_page_shift

From: Alexey Kardashevskiy <[email-masked]>
Date: Tue, 27 Oct 2015 16:56:10 +1100

On 10/24/2015 07:59 AM, Nishanth Aravamudan wrote:
> When DDW (Dynamic DMA Windows) are present for a device, we have stored
> the TCE (Translation Control Entry) size in a special device tree
> property. Check if we have enabled DDW for the device and return the TCE
> size from that property if present. If the property isn't present,
> fallback to looking the value up in struct iommu_table. If we don't find
> a iommu_table, fallback to the kernel's page size.
>
> Signed-off-by: Nishanth Aravamudan <[email-masked]>
> ---
>   arch/powerpc/platforms/pseries/iommu.c | 36 ++++++++++++++++++++++++++++++++++
>   1 file changed, 36 insertions(+)
>
> diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
> index 0946b98..1bf6471 100644
> --- a/arch/powerpc/platforms/pseries/iommu.c
> +++ b/arch/powerpc/platforms/pseries/iommu.c
> @@ -1292,6 +1292,40 @@ static u64 dma_get_required_mask_pSeriesLP(struct device *dev)
>   	return dma_iommu_ops.get_required_mask(dev);
>   }
>
> +static unsigned long dma_get_page_shift_pSeriesLP(struct device *dev)
> +{
> +	struct iommu_table *tbl;
> +
> +	if (!disable_ddw && dev_is_pci(dev)) {
> +		struct pci_dev *pdev = to_pci_dev(dev);
> +		struct device_node *dn;
> +
> +		dn = pci_device_to_OF_node(pdev);
> +
> +		/* search upwards for ibm,dma-window */
> +		for (; dn && PCI_DN(dn) && !PCI_DN(dn)->table_group;
> +				dn = dn->parent)
> +			if (of_get_property(dn, "ibm,dma-window", NULL))
> +				break;
> +		/*
> +		 * if there is a DDW configuration, the TCE shift is stored in
> +		 * the property
> +		 */
> +		if (dn && PCI_DN(dn)) {
> +			const struct dynamic_dma_window_prop *direct64 =
> +				of_get_property(dn, DIRECT64_PROPNAME, NULL);

This DIRECT64_PROPNAME property is only present under pHyp, QEMU/KVM does 
not set it as 64bit windows are dynamic there so something like 
find_existing_ddw() needs to be used here.

> +			if (direct64)
> +				return be32_to_cpu(direct64->tce_shift);
> +		}
> +	}
> +
> +	tbl = get_iommu_table_base(dev);
> +	if (tbl)
> +		return tbl->it_page_shift;
> +
> +	return PAGE_SHIFT;
> +}
> +
>   #else  /* CONFIG_PCI */
>   #define pci_dma_bus_setup_pSeries	NULL
>   #define pci_dma_dev_setup_pSeries	NULL
> @@ -1299,6 +1333,7 @@ static u64 dma_get_required_mask_pSeriesLP(struct device *dev)
>   #define pci_dma_dev_setup_pSeriesLP	NULL
>   #define dma_set_mask_pSeriesLP		NULL
>   #define dma_get_required_mask_pSeriesLP	NULL
> +#define dma_get_page_shift_pSeriesLP	NULL
>   #endif /* !CONFIG_PCI */
>
>   static int iommu_mem_notifier(struct notifier_block *nb, unsigned long action,
> @@ -1395,6 +1430,7 @@ void iommu_init_early_pSeries(void)
>   		pseries_pci_controller_ops.dma_dev_setup = pci_dma_dev_setup_pSeriesLP;
>   		ppc_md.dma_set_mask = dma_set_mask_pSeriesLP;
>   		ppc_md.dma_get_required_mask = dma_get_required_mask_pSeriesLP;
> +		ppc_md.dma_get_page_shift = dma_get_page_shift_pSeriesLP;
>   	} else {
>   		pseries_pci_controller_ops.dma_bus_setup = pci_dma_bus_setup_pSeries;
>   		pseries_pci_controller_ops.dma_dev_setup = pci_dma_dev_setup_pSeries;
>

-- 
Alexey