[PATCH v4 2/2] PCI: dwc: Add support for 64-bit MSI target address

From: Will McVicker
Date: Thu Aug 11 2022 - 20:04:00 EST


Since not all devices require a 32-bit MSI address, add support to the
PCIe host driver to allow setting the DMA mask to 64-bits. This allows
kernels to disable ZONE_DMA32 and bounce buffering (swiotlb) without
risking not being able to get a 32-bit address during DMA allocation.
Basically, in the slim chance that there are no 32-bit allocations
available, the current PCIe host driver will fail to allocate the
msi_msg page due to a DMA address overflow (seen in [1]). With this
patch, the PCIe device can advertise 64-bit support via its MSI
capabilities to hint to the PCIe host driver to set the DMA mask to
64-bits.

[1] https://lore.kernel.org/all/Yo0soniFborDl7+C@xxxxxxxxxx/

Reported-by: kernel test robot <lkp@xxxxxxxxx>
Signed-off-by: Will McVicker <willmcvicker@xxxxxxxxxx>
Reviewed-by: Rob Herring <robh@xxxxxxxxxx>
---
drivers/pci/controller/dwc/pcie-designware-host.c | 14 ++++++++++++--
drivers/pci/controller/dwc/pcie-designware.c | 8 ++++++++
drivers/pci/controller/dwc/pcie-designware.h | 1 +
3 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index 39f3b37d4033..d7831040791b 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -330,6 +330,8 @@ static int dw_pcie_msi_host_init(struct dw_pcie_rp *pp)
u64 *msi_vaddr;
int ret;
u32 ctrl, num_ctrls;
+ bool msi_64bit = false;
+ u16 msi_capabilities;

for (ctrl = 0; ctrl < MAX_MSI_CTRLS; ctrl++)
pp->irq_mask[ctrl] = ~0;
@@ -367,9 +369,17 @@ static int dw_pcie_msi_host_init(struct dw_pcie_rp *pp)
dw_chained_msi_isr, pp);
}

- ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32));
+ msi_capabilities = dw_pcie_msi_capabilities(pci);
+ if (msi_capabilities & PCI_MSI_FLAGS_ENABLE)
+ msi_64bit = msi_capabilities & PCI_MSI_FLAGS_64BIT;
+
+ dev_dbg(dev, "Setting MSI DMA mask to %s-bit.\n",
+ msi_64bit ? "64" : "32");
+ ret = dma_set_mask_and_coherent(dev, msi_64bit ?
+ DMA_BIT_MASK(64) : DMA_BIT_MASK(32));
if (ret)
- dev_warn(dev, "Failed to set DMA mask to 32-bit. Devices with only 32-bit MSI support may not work properly\n");
+ dev_warn(dev, "Failed to set DMA mask to %s-bit.\n",
+ msi_64bit ? "64" : "32");

msi_vaddr = dmam_alloc_coherent(dev, sizeof(u64), &pp->msi_data,
GFP_KERNEL);
diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index c6725c519a47..650a7f22f9d0 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -82,6 +82,14 @@ u8 dw_pcie_find_capability(struct dw_pcie *pci, u8 cap)
}
EXPORT_SYMBOL_GPL(dw_pcie_find_capability);

+u16 dw_pcie_msi_capabilities(struct dw_pcie *pci)
+{
+ u8 offset;
+
+ offset = dw_pcie_find_capability(pci, PCI_CAP_ID_MSI);
+ return dw_pcie_readw_dbi(pci, offset + PCI_MSI_FLAGS);
+}
+
static u16 dw_pcie_find_next_ext_capability(struct dw_pcie *pci, u16 start,
u8 cap)
{
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index a871ae7eb59e..45fcdfc8c035 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -332,6 +332,7 @@ void dw_pcie_version_detect(struct dw_pcie *pci);

u8 dw_pcie_find_capability(struct dw_pcie *pci, u8 cap);
u16 dw_pcie_find_ext_capability(struct dw_pcie *pci, u8 cap);
+u16 dw_pcie_msi_capabilities(struct dw_pcie *pci);

int dw_pcie_read(void __iomem *addr, int size, u32 *val);
int dw_pcie_write(void __iomem *addr, int size, u32 val);
--
2.37.1.559.g78731f0fdb-goog