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For CMA-backed allocations, the guaranteed physical > alignment is capped at PAGE_SIZE << CONFIG_CMA_ALIGNMENT. With a direct > DMA mapping, 4 KiB pages, and CONFIG_CMA_ALIGNMENT=8, a 2 MiB BAR may > therefore receive a DMA address aligned to only 1 MiB. > dw_pcie_prog_ep_inbound_atu() rejects such a mapping with -EINVAL. > > If the initial allocation is misaligned, free it and retry with > mem_size - 1 bytes of padding. Select an aligned subrange and record its > offset so pci_epf_free_space() can pass the original CPU address, DMA > handle, and size to dma_free_coherent(). I understand this situation, but it mays waste memory, if 16MiB, it max waste 16M-1 space. As workaround, this is good enough. add dt memory node for pcie-ep my_dma_pool: dma@42000000 { compatible = "shared-dma-pool"; reg = <0x42000000 0x02000000>; reusable; /* <-- CMA: system CAN use these pages when idle */ }; pcie-ep { ... memory-region = <&my_dma_pool>; } but if use "reusable", still meet CONFIG_CMA_ALIGNMENT. if use "no-map", dma_alloc_from_dev_coherent() will bypass CONFIG_CMA_ALIGNMENT. but it will waste memory if not use pcie-ep devices. Maybe we try static int __init rmem_cma_setup(unsigned long node, struct reserved_mem *rmem) { ... ret = cma_init_reserved_mem(rmem->base, rmem->size, 0, rmem->name, &cma); if (ret) { ... } + /* linux,cma-force-align: bypass CONFIG_CMA_ALIGNMENT cap, align = get_order(size) */ + if (of_get_flat_dt_prop(node, "linux,cma-force-align", NULL)) + cma->force_align = true; if (default_cma) dma_contiguous_default_area = cma; ... } static struct page *cma_alloc_aligned(struct cma *cma, size_t size, gfp_t gfp) { - unsigned int align = min(get_order(size), CONFIG_CMA_ALIGNMENT); + unsigned int align; + + if (cma && cma->force_align) + align = get_order(size); /* no cap: align = natural power-of-2 for size */ + else + align = min(get_order(size), CONFIG_CMA_ALIGNMENT); return cma_alloc(cma, size >> PAGE_SHIFT, align, gfp & __GFP_NOWARN); } I am not sure if DT team accept add "linux,cma-force-align", which desgin for specic device CMA region only, not for default cmd. No impact to other system. Frank > > Fixes: 5e8cb4033807 ("PCI: endpoint: Add EP core layer to enable EP controller and EP functions") > Signed-off-by: Koichiro Den > --- > drivers/pci/endpoint/pci-epf-core.c | 39 +++++++++++++++++++++++------ > include/linux/pci-epf.h | 7 ++++-- > 2 files changed, 37 insertions(+), 9 deletions(-) > > diff --git a/drivers/pci/endpoint/pci-epf-core.c b/drivers/pci/endpoint/pci-epf-core.c > index 6987343c9e61..e8c3709d85c4 100644 > --- a/drivers/pci/endpoint/pci-epf-core.c > +++ b/drivers/pci/endpoint/pci-epf-core.c > @@ -8,6 +8,7 @@ > > #include > #include > +#include > #include > #include > > @@ -278,13 +279,15 @@ void pci_epf_free_space(struct pci_epf *epf, void *addr, enum pci_barno bar, > } > > dev = epc->dev.parent; > - dma_free_coherent(dev, epf_bar[bar].mem_size, addr, > - epf_bar[bar].phys_addr); > + dma_free_coherent(dev, epf_bar[bar].mem_size, > + (u8 *)addr - epf_bar[bar].alloc_offset, > + epf_bar[bar].phys_addr - epf_bar[bar].alloc_offset); > > epf_bar[bar].phys_addr = 0; > epf_bar[bar].addr = NULL; > epf_bar[bar].size = 0; > epf_bar[bar].mem_size = 0; > + epf_bar[bar].alloc_offset = 0; > epf_bar[bar].barno = 0; > epf_bar[bar].flags = 0; > } > @@ -308,8 +311,10 @@ void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar, > { > struct pci_epf_bar *epf_bar; > dma_addr_t phys_addr; > + size_t alloc_offset = 0; > struct pci_epc *epc; > struct device *dev; > + size_t alloc_size; > size_t mem_size; > void *space; > > @@ -326,16 +331,31 @@ void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar, > } > > dev = epc->dev.parent; > - space = dma_alloc_coherent(dev, mem_size, &phys_addr, GFP_KERNEL); > - if (!space) { > - dev_err(dev, "failed to allocate mem space\n"); > - return NULL; > + alloc_size = mem_size; > + space = dma_alloc_coherent(dev, alloc_size, &phys_addr, GFP_KERNEL); > + if (!space) > + goto err_alloc; > + if (!IS_ALIGNED(phys_addr, mem_size)) { > + dma_free_coherent(dev, alloc_size, space, phys_addr); > + > + if (check_add_overflow(mem_size, mem_size - 1, &alloc_size)) > + return NULL; > + > + space = dma_alloc_coherent(dev, alloc_size, &phys_addr, > + GFP_KERNEL); > + if (!space) > + goto err_alloc; > + > + alloc_offset = ALIGN(phys_addr, mem_size) - phys_addr; > + space = (u8 *)space + alloc_offset; > + phys_addr += alloc_offset; > } > > epf_bar[bar].phys_addr = phys_addr; > epf_bar[bar].addr = space; > epf_bar[bar].size = size; > - epf_bar[bar].mem_size = mem_size; > + epf_bar[bar].mem_size = alloc_size; > + epf_bar[bar].alloc_offset = alloc_offset; > epf_bar[bar].barno = bar; > if (upper_32_bits(size) || epc_features->bar[bar].only_64bit) > epf_bar[bar].flags |= PCI_BASE_ADDRESS_MEM_TYPE_64; > @@ -343,6 +363,10 @@ void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar, > epf_bar[bar].flags |= PCI_BASE_ADDRESS_MEM_TYPE_32; > > return space; > + > +err_alloc: > + dev_err(dev, "failed to allocate mem space\n"); > + return NULL; > } > EXPORT_SYMBOL_GPL(pci_epf_alloc_space); > > @@ -413,6 +437,7 @@ int pci_epf_assign_bar_space(struct pci_epf *epf, size_t size, > epf_bar[bar].addr = NULL; > epf_bar[bar].size = bar_size; > epf_bar[bar].mem_size = aligned_mem_size; > + epf_bar[bar].alloc_offset = 0; > epf_bar[bar].barno = bar; > if (upper_32_bits(size) || epc_features->bar[bar].only_64bit) > epf_bar[bar].flags |= PCI_BASE_ADDRESS_MEM_TYPE_64; > diff --git a/include/linux/pci-epf.h b/include/linux/pci-epf.h > index 8a6c64a35890..749c6611d7b9 100644 > --- a/include/linux/pci-epf.h > +++ b/include/linux/pci-epf.h > @@ -131,8 +131,10 @@ struct pci_epf_bar_submap { > * @phys_addr: physical address that should be mapped to the BAR > * @addr: virtual address corresponding to the @phys_addr > * @size: the size of the address space present in BAR > - * @mem_size: the size actually allocated to accommodate the iATU alignment > - * requirement > + * @mem_size: size of the coherent allocation, including alignment padding, or > + * the required aligned backing size for assigned BAR space > + * @alloc_offset: offset from the coherent allocation's CPU and DMA base > + * addresses to @addr and @phys_addr > * @barno: BAR number > * @flags: flags that are set for the BAR > * @num_submap: number of entries in @submap > @@ -144,6 +146,7 @@ struct pci_epf_bar { > void *addr; > size_t size; > size_t mem_size; > + size_t alloc_offset; > enum pci_barno barno; > int flags; > > > base-commit: 0a6f72eda328c773324555491e1ad7f0b0153155 > -- > 2.51.0 >