On 08/10/2022, Rob Herring wrote:
> 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
> >
Thanks for the review Rob! I've updated the series to address your concerns.
Regards,
Will
