Messages in this thread | | | Date | Tue, 30 Oct 2018 13:58:41 +0100 | From | Christoph Hellwig <> | Subject | Re: [PATCH] powerpc/npu-dma: Remove NPU DMA ops |
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Please take my patch instead. We have a kernel polcity to not keep dead code around, and everyone including Linus and the attending IBMers confirmed this.
On Tue, Oct 30, 2018 at 10:02:03PM +1100, Alistair Popple wrote: > The NPU IOMMU is setup to mirror the parent PCIe device IOMMU > setup. Therefore it does not make sense to call dma operations such as > dma_map_page, etc. directly on these devices. The existing dma-ops > simply print a warning if they are ever called, however this is > unnecessary and the warnings are likely to go unnoticed. > > It is instead simpler to remove these operations and let the generic > DMA code print warnings (eg. via a NULL pointer deref) in cases of > buggy drivers attempting dma operations on NVLink devices. > > Signed-off-by: Alistair Popple <alistair@popple.id.au> > --- > arch/powerpc/platforms/powernv/npu-dma.c | 64 ++------------------------------ > 1 file changed, 4 insertions(+), 60 deletions(-) > > diff --git a/arch/powerpc/platforms/powernv/npu-dma.c b/arch/powerpc/platforms/powernv/npu-dma.c > index 6f60e0931922..75b935252981 100644 > --- a/arch/powerpc/platforms/powernv/npu-dma.c > +++ b/arch/powerpc/platforms/powernv/npu-dma.c > @@ -102,63 +102,6 @@ struct pci_dev *pnv_pci_get_npu_dev(struct pci_dev *gpdev, int index) > } > EXPORT_SYMBOL(pnv_pci_get_npu_dev); > > -#define NPU_DMA_OP_UNSUPPORTED() \ > - dev_err_once(dev, "%s operation unsupported for NVLink devices\n", \ > - __func__) > - > -static void *dma_npu_alloc(struct device *dev, size_t size, > - dma_addr_t *dma_handle, gfp_t flag, > - unsigned long attrs) > -{ > - NPU_DMA_OP_UNSUPPORTED(); > - return NULL; > -} > - > -static void dma_npu_free(struct device *dev, size_t size, > - void *vaddr, dma_addr_t dma_handle, > - unsigned long attrs) > -{ > - NPU_DMA_OP_UNSUPPORTED(); > -} > - > -static dma_addr_t dma_npu_map_page(struct device *dev, struct page *page, > - unsigned long offset, size_t size, > - enum dma_data_direction direction, > - unsigned long attrs) > -{ > - NPU_DMA_OP_UNSUPPORTED(); > - return 0; > -} > - > -static int dma_npu_map_sg(struct device *dev, struct scatterlist *sglist, > - int nelems, enum dma_data_direction direction, > - unsigned long attrs) > -{ > - NPU_DMA_OP_UNSUPPORTED(); > - return 0; > -} > - > -static int dma_npu_dma_supported(struct device *dev, u64 mask) > -{ > - NPU_DMA_OP_UNSUPPORTED(); > - return 0; > -} > - > -static u64 dma_npu_get_required_mask(struct device *dev) > -{ > - NPU_DMA_OP_UNSUPPORTED(); > - return 0; > -} > - > -static const struct dma_map_ops dma_npu_ops = { > - .map_page = dma_npu_map_page, > - .map_sg = dma_npu_map_sg, > - .alloc = dma_npu_alloc, > - .free = dma_npu_free, > - .dma_supported = dma_npu_dma_supported, > - .get_required_mask = dma_npu_get_required_mask, > -}; > - > /* > * Returns the PE assoicated with the PCI device of the given > * NPU. Returns the linked pci device if pci_dev != NULL. > @@ -270,10 +213,11 @@ static void pnv_npu_dma_set_32(struct pnv_ioda_pe *npe) > rc = pnv_npu_set_window(npe, 0, gpe->table_group.tables[0]); > > /* > - * We don't initialise npu_pe->tce32_table as we always use > - * dma_npu_ops which are nops. > + * NVLink devices use the same TCE table configuration as > + * their parent device so drivers shouldn't be doing DMA > + * operations directly on these devices. > */ > - set_dma_ops(&npe->pdev->dev, &dma_npu_ops); > + set_dma_ops(&npe->pdev->dev, NULL); > } > > /* > -- > 2.11.0 ---end quoted text---
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