[PATCH v1 1/2] PCI: dwc: drop dependency on ZONE_DMA32

From: Will McVicker
Date: Tue Aug 09 2022 - 14:02:18 EST


Re-work the msi_msg DMA allocation logic to use dma_alloc_coherent()
which uses the coherent DMA mask to try and return an allocation within
the DMA mask limits. This allows kernel configurations that disable
ZONE_DMA32 to continue supporting a 32-bit DMA mask. Without this patch,
the PCIe host device will fail to probe when ZONE_DMA32 is disabled.

Fixes: 35797e672ff0 ("PCI: dwc: Fix MSI msi_msg DMA mapping")
Signed-off-by: Will McVicker <willmcvicker@xxxxxxxxxx>
---
.../pci/controller/dwc/pcie-designware-host.c | 28 +++++++++----------
1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
index 7746f94a715f..0cfc3c098f13 100644
--- a/drivers/pci/controller/dwc/pcie-designware-host.c
+++ b/drivers/pci/controller/dwc/pcie-designware-host.c
@@ -272,9 +272,9 @@ static void dw_pcie_free_msi(struct dw_pcie_rp *pp)
struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
struct device *dev = pci->dev;

- dma_unmap_page(dev, pp->msi_data, PAGE_SIZE, DMA_FROM_DEVICE);
- if (pp->msi_page)
- __free_page(pp->msi_page);
+ dma_free_coherent(dev, PAGE_SIZE, pp->msi_page, pp->msi_data);
+ pp->msi_data = 0;
+ pp->msi_page = NULL;
}
}

@@ -375,22 +375,22 @@ static int dw_pcie_msi_host_init(struct dw_pcie_rp *pp)
dw_chained_msi_isr, pp);
}

- ret = dma_set_mask(dev, DMA_BIT_MASK(32));
+ ret = dma_set_mask_and_coherent(dev, 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");

- pp->msi_page = alloc_page(GFP_DMA32);
- pp->msi_data = dma_map_page(dev, pp->msi_page, 0,
- PAGE_SIZE, DMA_FROM_DEVICE);
- ret = dma_mapping_error(dev, pp->msi_data);
- if (ret) {
- dev_err(pci->dev, "Failed to map MSI data\n");
- __free_page(pp->msi_page);
- pp->msi_page = NULL;
+ pp->msi_page = dma_alloc_coherent(dev, PAGE_SIZE, &pp->msi_data,
+ GFP_KERNEL);
+ if (!pp->msi_page || dma_mapping_error(dev, pp->msi_data)) {
+ dev_err(dev, "Failed to alloc and map MSI data\n");
+ if (pp->msi_page) {
+ dma_free_coherent(dev, PAGE_SIZE, pp->msi_page,
+ pp->msi_data);
+ pp->msi_page = NULL;
+ }
pp->msi_data = 0;
dw_pcie_free_msi(pp);
-
- return ret;
+ return -ENOMEM;
}

return 0;
--
2.37.1.559.g78731f0fdb-goog