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powerpc/powernv/pci: Enable 64-bit devices to access >4GB DMA space

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On PHB3/POWER8 systems, devices can select between two different sections
of address space, TVE#0 and TVE#1.  TVE#0 is intended for 32bit devices
that aren't capable of addressing more than 4GB.  Selecting TVE#1 instead,
with the capability of addressing over 4GB, is performed by setting bit 59
of a PCI address.

However, some devices aren't capable of addressing at least 59 bits, but
still want more than 4GB of DMA space.  In order to enable this, reconfigure
TVE#0 to be suitable for 64-bit devices by allocating memory past the
initial 4GB that is inaccessible by 64-bit DMAs.

This bypass mode is only enabled if a device requests 4GB or more of DMA
address space, if the system has PHB3 (POWER8 systems), and if the device
does not share a PE with any devices from different vendors.

Signed-off-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Russell Currey 2017-06-21 17:18:04 +10:00 committed by Michael Ellerman
parent a0f98629f1
commit 8e3f1b1d82
1 changed files with 91 additions and 2 deletions
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93
arch/powerpc/platforms/powernv/pci-ioda.c
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@ -1743,6 +1743,75 @@ static bool pnv_pci_ioda_pe_single_vendor(struct pnv_ioda_pe *pe)
return true;
}
/*
* Reconfigure TVE#0 to be usable as 64-bit DMA space.
*
* The first 4GB of virtual memory for a PE is reserved for 32-bit accesses.
* Devices can only access more than that if bit 59 of the PCI address is set
* by hardware, which indicates TVE#1 should be used instead of TVE#0.
* Many PCI devices are not capable of addressing that many bits, and as a
* result are limited to the 4GB of virtual memory made available to 32-bit
* devices in TVE#0.
*
* In order to work around this, reconfigure TVE#0 to be suitable for 64-bit
* devices by configuring the virtual memory past the first 4GB inaccessible
* by 64-bit DMAs. This should only be used by devices that want more than
* 4GB, and only on PEs that have no 32-bit devices.
*
* Currently this will only work on PHB3 (POWER8).
*/
static int pnv_pci_ioda_dma_64bit_bypass(struct pnv_ioda_pe *pe)
{
u64 window_size, table_size, tce_count, addr;
struct page *table_pages;
u64 tce_order = 28; /* 256MB TCEs */
__be64 *tces;
s64 rc;
/*
* Window size needs to be a power of two, but needs to account for
* shifting memory by the 4GB offset required to skip 32bit space.
*/
window_size = roundup_pow_of_two(memory_hotplug_max() + (1ULL << 32));
tce_count = window_size >> tce_order;
table_size = tce_count << 3;
if (table_size < PAGE_SIZE)
table_size = PAGE_SIZE;
table_pages = alloc_pages_node(pe->phb->hose->node, GFP_KERNEL,
get_order(table_size));
if (!table_pages)
goto err;
tces = page_address(table_pages);
if (!tces)
goto err;
memset(tces, 0, table_size);
for (addr = 0; addr < memory_hotplug_max(); addr += (1 << tce_order)) {
tces[(addr + (1ULL << 32)) >> tce_order] =
cpu_to_be64(addr | TCE_PCI_READ | TCE_PCI_WRITE);
}
rc = opal_pci_map_pe_dma_window(pe->phb->opal_id,
pe->pe_number,
/* reconfigure window 0 */
(pe->pe_number << 1) + 0,
1,
__pa(tces),
table_size,
1 << tce_order);
if (rc == OPAL_SUCCESS) {
pe_info(pe, "Using 64-bit DMA iommu bypass (through TVE#0)\n");
return 0;
}
err:
pe_err(pe, "Error configuring 64-bit DMA bypass\n");
return -EIO;
}
static int pnv_pci_ioda_dma_set_mask(struct pci_dev *pdev, u64 dma_mask)
{
struct pci_controller *hose = pci_bus_to_host(pdev->bus);
@ -1751,6 +1820,7 @@ static int pnv_pci_ioda_dma_set_mask(struct pci_dev *pdev, u64 dma_mask)
struct pnv_ioda_pe *pe;
uint64_t top;
bool bypass = false;
s64 rc;
if (WARN_ON(!pdn || pdn->pe_number == IODA_INVALID_PE))
return -ENODEV;;
@ -1765,8 +1835,27 @@ static int pnv_pci_ioda_dma_set_mask(struct pci_dev *pdev, u64 dma_mask)
dev_info(&pdev->dev, "Using 64-bit DMA iommu bypass\n");
set_dma_ops(&pdev->dev, &dma_direct_ops);
} else {
dev_info(&pdev->dev, "Using 32-bit DMA via iommu\n");
set_dma_ops(&pdev->dev, &dma_iommu_ops);
/*
* If the device can't set the TCE bypass bit but still wants
* to access 4GB or more, on PHB3 we can reconfigure TVE#0 to
* bypass the 32-bit region and be usable for 64-bit DMAs.
* The device needs to be able to address all of this space.
*/
if (dma_mask >> 32 &&
dma_mask > (memory_hotplug_max() + (1ULL << 32)) &&
pnv_pci_ioda_pe_single_vendor(pe) &&
phb->model == PNV_PHB_MODEL_PHB3) {
/* Configure the bypass mode */
rc = pnv_pci_ioda_dma_64bit_bypass(pe);
if (rc)
return rc;
/* 4GB offset bypasses 32-bit space */
set_dma_offset(&pdev->dev, (1ULL << 32));
set_dma_ops(&pdev->dev, &dma_direct_ops);
} else {
dev_info(&pdev->dev, "Using 32-bit DMA via iommu\n");
set_dma_ops(&pdev->dev, &dma_iommu_ops);
}
}
*pdev->dev.dma_mask = dma_mask;