On Wed, Aug 10, 2022 at 06:35:34PM +0000, Will McVicker wrote:
> 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")
> Reported-by: Isaac J. Manjarres <isaacmanjarres@xxxxxxxxxx>
> Signed-off-by: Will McVicker <willmcvicker@xxxxxxxxxx>
> ---
> .../pci/controller/dwc/pcie-designware-host.c | 23 ++++++++-----------
> 1 file changed, 9 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..8f2222f51671 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 +375,17 @@ 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);
You can use the managed version, dmam_alloc_coherent(), and avoid the
freeing yourself. Also with that, I think you don't need 'msi_page'?
Also, no need to alloc a whole page. A u32 or u64? should be fine. The
write never makes it to memory, so doesn't really matter.
> + if (!pp->msi_page) {
> + dev_err(dev, "Failed to alloc and map MSI data\n");
> pp->msi_data = 0;
> dw_pcie_free_msi(pp);
> -
> - return ret;
> + return -ENOMEM;
> }
>
> return 0;
> --
> 2.37.1.559.g78731f0fdb-goog
>
