On Thu, Aug 25, 2022 at 06:50:24PM +0000, Will McVicker wrote: > Re-work the msi_msg DMA allocation logic to use dmam_alloc_coherent() which > uses the coherent DMA mask to try to return an allocation within the DMA > mask limits. With that, we now can drop the msi_page parameter in struct > dw_pcie_rp. 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. As Rob already said here https://lore.kernel.org/all/CAL_JsqJh=d-B51b6yPBRq0tOwbChN=AFPr-a19U1QdQZAE7c1A@xxxxxxxxxxxxxx/ and I mentioned in this thread https://lore.kernel.org/linux-pci/20220912000211.ct6asuhhmnatje5e@mobilestation/ DW PCIe MSI doesn't cause any DMA due to the way the iMSI-RX engine is designed. So reserving any real system memory is a waste of one in this case. Reserving DMA-coherent even more inappropriate since it can be expensive on some platforms (see note in Part Ia of Documentation/core-api/dma-api.rst). For instance on MIPS32 with non-corehent common DMA. > > Fixes: 35797e672ff0 ("PCI: dwc: Fix MSI msi_msg DMA mapping") > Reported-by: Isaac J. Manjarres <isaacmanjarres@xxxxxxxxxx> > Signed-off-by: Will McVicker <willmcvicker@xxxxxxxxxx> > Acked-by: Jingoo Han <jingoohan1@xxxxxxxxx> > Reviewed-by: Rob Herring <robh@xxxxxxxxxx> > --- > .../pci/controller/dwc/pcie-designware-host.c | 28 +++++-------------- > drivers/pci/controller/dwc/pcie-designware.h | 1 - > 2 files changed, 7 insertions(+), 22 deletions(-) > > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c > index 7746f94a715f..39f3b37d4033 100644 > --- a/drivers/pci/controller/dwc/pcie-designware-host.c > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c > @@ -267,15 +267,6 @@ static void dw_pcie_free_msi(struct dw_pcie_rp *pp) > > irq_domain_remove(pp->msi_domain); > irq_domain_remove(pp->irq_domain); > - > - if (pp->msi_data) { > - 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); > - } > } > > static void dw_pcie_msi_init(struct dw_pcie_rp *pp) > @@ -336,6 +327,7 @@ static int dw_pcie_msi_host_init(struct dw_pcie_rp *pp) > struct dw_pcie *pci = to_dw_pcie_from_pp(pp); > struct device *dev = pci->dev; > struct platform_device *pdev = to_platform_device(dev); > + u64 *msi_vaddr; > int ret; > u32 ctrl, num_ctrls; > > @@ -375,22 +367,16 @@ 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)); This has been redundant in the first place since none of the DW PCIe low-level drivers update the mask, and it's of 32-bits wide by default anyway: https://elixir.bootlin.com/linux/latest/source/drivers/of/platform.c#L167 > 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_data = 0; > + msi_vaddr = dmam_alloc_coherent(dev, sizeof(u64), &pp->msi_data, > + GFP_KERNEL); Changing the whole device DMA-mask due to something that doesn't perform seems inappropriate. I'd suggest to preserve the ZONE_DMA32 here until there is something like suggested by @Robin https://lore.kernel.org/linux-pci/1e63a581-14ae-b4b5-a5bf-ca8f09c33af6@xxxxxxx/ in the last paragraph is implemented. Especially seeing there still common drivers in kernel which still rely on that zone. -Sergey > + if (!msi_vaddr) { > + dev_err(dev, "Failed to alloc and map MSI data\n"); > dw_pcie_free_msi(pp); > - > - return ret; > + return -ENOMEM; > } > > return 0; > diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h > index 09b887093a84..a871ae7eb59e 100644 > --- a/drivers/pci/controller/dwc/pcie-designware.h > +++ b/drivers/pci/controller/dwc/pcie-designware.h > @@ -243,7 +243,6 @@ struct dw_pcie_rp { > struct irq_domain *irq_domain; > struct irq_domain *msi_domain; > dma_addr_t msi_data; > - struct page *msi_page; > struct irq_chip *msi_irq_chip; > u32 num_vectors; > u32 irq_mask[MAX_MSI_CTRLS]; > -- > 2.37.2.672.g94769d06f0-goog > >
