Hi Nicolas, I'm hoping Christoph will chime in and one of the x86 guys will merge this, since I'm not a DMA expert. Trivial comments/questions below.
On Wed, Oct 16, 2019 at 06:51:37PM +0200, Nicolas Saenz Julienne wrote: > The devices found behind this PCIe chip have unusual DMA mapping > constraints as there is an AMBA interconnect placed in between them and > the different PCI endpoints. The offset between physical memory > addresses and AMBA's view is provided by reading a PCI config register, > which is saved and used whenever DMA mapping is needed. > > It turns out that this DMA setup can be represented by properly setting > 'dma_pfn_offset', 'dma_bus_mask' and 'dma_mask' during the PCI device > enable fixup. And ultimately allows us to get rid of this device's > custom DMA functions. > > Aside from the code deletion and DMA setup, sta2x11_pdev_to_mapping() is > moved to avoid warnings whenever CONFIG_PM is not enabled. > > Signed-off-by: Nicolas Saenz Julienne <nsaenzjulie...@suse.de> > - pci_read_config_dword(pdev, AHB_BASE(0), &map->amba_base); > + > + pci_read_config_dword(pdev, AHB_BASE(0), &amba_base); > + dev->dma_pfn_offset = PFN_DOWN(-amba_base); > + dev->bus_dma_mask = amba_base + STA2X11_AMBA_SIZE - 1; I think of a mask as typically being one less than a power of two, but that's not the case here, e.g., STA2X11_AMBA_SIZE - 1 == 0x1fffffff (512MB-1), so if amba_size is 1G, the mask will be 0x5fffffff. Just double-checking to be sure that's what you intend. > + pci_set_consistent_dma_mask(pdev, amba_base + STA2X11_AMBA_SIZE - 1); > + pci_set_dma_mask(pdev, amba_base + STA2X11_AMBA_SIZE - 1); Maybe add a local variable instead of repeating the "amba_base + ..." expression three times? > /* Configure AHB mapping */ > pci_write_config_dword(pdev, AHB_PEXLBASE(0), 0); > @@ -252,14 +156,25 @@ static void sta2x11_map_ep(struct pci_dev *pdev) > pci_write_config_dword(pdev, AHB_CRW(i), 0); > > dev_info(&pdev->dev, > - "sta2x11: Map EP %i: AMBA address %#8x-%#8x\n", > - sta2x11_pdev_to_ep(pdev), map->amba_base, > - map->amba_base + STA2X11_AMBA_SIZE - 1); > + "sta2x11: Map EP %i: AMBA address %#8x-%#8llx\n", > + sta2x11_pdev_to_ep(pdev), amba_base, dev->bus_dma_mask); This would read better as amba_base, amba_base + STA2X11_AMBA_SIZE - 1 I know that's the same dev->bus_dma_mask, but a "mask" is not the obvious name for the end of a range.
