On Fri, Oct 04, 2024 at 02:07:38PM +0900, Damien Le Moal wrote:
> Some endpoint controllers have requirements on the alignment of the
> controller physical memory address that must be used to map a RC PCI
> address region. For instance, the rockchip endpoint controller uses
> at most the lower 20 bits of a physical memory address region as the
> lower bits of an RC PCI address. For mapping a PCI address region of
> size bytes starting from pci_addr, the exact number of address bits
> used is the number of address bits changing in the address range
> [pci_addr..pci_addr + size - 1].
>
> For this example, this creates the following constraints:
> 1) The offset into the controller physical memory allocated for a
> mapping depends on the mapping size *and* the starting PCI address
> for the mapping.
> 2) A mapping size cannot exceed the controller windows size (1MB) minus
> the offset needed into the allocated physical memory, which can end
> up being a smaller size than the desired mapping size.
>
> Handling these constraints independently of the controller being used
> in an endpoint function driver is not possible with the current EPC
> API as only the ->align field in struct pci_epc_features is provided
> and used for BAR (inbound ATU mappings) mapping. A new API is needed
> for function drivers to discover mapping constraints and handle
> non-static requirements based on the RC PCI address range to access.
>
> Introduce the function pci_epc_map_align() and the endpoint controller
> operation ->map_align to allow endpoint function drivers to obtain the
> size and the offset into a controller address region that must be
> allocated and mapped to access an RC PCI address region. The size
> of the mapping provided by pci_epc_map_align() can then be used as the
> size argument for the function pci_epc_mem_alloc_addr().
> The offset into the allocated controller memory provided can be used to
> correctly handle data transfers.
>
> For endpoint controllers that have PCI address alignment constraints,
> pci_epc_map_align() may indicate upon return an effective PCI address
> region mapping size that is smaller (but not 0) than the requested PCI
> address region size. For such case, an endpoint function driver must
> handle data accesses over the desired PCI address range in fragments,
> by repeatedly using pci_epc_map_align() over the PCI address range.
>
> The controller operation ->map_align is optional: controllers that do
> not have any alignment constraints for mapping a RC PCI address region
> do not need to implement this operation. For such controllers,
> pci_epc_map_align() always returns the mapping size as equal to the
> requested size of the PCI region and an offset equal to 0.
>
> The new structure struct pci_epc_map is introduced to represent a
> mapping start PCI address, mapping effective size, the size and offset
> into the controller memory needed for mapping the PCI address region as
> well as the physical and virtual CPU addresses of the mapping (phys_base
> and virt_base fields). For convenience, the physical and virtual CPU
> addresses within that mapping to access the target RC PCI address region
> are also provided (phys_addr and virt_addr fields).
>
> Co-developed-by: Rick Wertenbroek <rick.wertenbroek@xxxxxxxxx>
> Signed-off-by: Rick Wertenbroek <rick.wertenbroek@xxxxxxxxx>
> Signed-off-by: Damien Le Moal <dlemoal@xxxxxxxxxx>
> ---
> drivers/pci/endpoint/pci-epc-core.c | 56 +++++++++++++++++++++++++++++
> include/linux/pci-epc.h | 37 +++++++++++++++++++
> 2 files changed, 93 insertions(+)
>
> diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
> index b854f1bab26f..48dd3c28ac4c 100644
> --- a/drivers/pci/endpoint/pci-epc-core.c
> +++ b/drivers/pci/endpoint/pci-epc-core.c
> @@ -435,6 +435,62 @@ void pci_epc_unmap_addr(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> }
> EXPORT_SYMBOL_GPL(pci_epc_unmap_addr);
>
> +/**
> + * pci_epc_map_align() - Get the offset into and the size of a controller memory
> + * address region needed to map a RC PCI address region
> + * @epc: the EPC device on which address is allocated
> + * @func_no: the physical endpoint function number in the EPC device
> + * @vfunc_no: the virtual endpoint function number in the physical function
> + * @pci_addr: The RC PCI address to map
> + * @pci_size: the number of bytes to map starting from @pci_addr
> + * @map: populate here the actual size and offset into the controller memory
> + * that must be allocated for the mapping
> + *
> + * If defined, invoke the controller map_align operation to obtain the size and
> + * the offset into a controller address region that must be allocated to map
> + * @pci_size bytes of the RC PCI address space starting from @pci_addr.
> + *
> + * On return, @map->pci_size indicates the effective size of the mapping that
> + * can be handled by the controller. This size may be smaller than the requested
> + * @pci_size. In such case, the endpoint function driver must handle the mapping
> + * using several fragments. The offset into the controller memory for the
> + * effective mapping of the RC PCI address range
> + * @pci_addr..@pci_addr+@map->pci_size is indicated by @map->map_ofst.
> + *
> + * If the target controller does not define a map_align operation, it is assumed
> + * that the controller has no PCI address mapping alignment constraint.
> + */
> +int pci_epc_map_align(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> + u64 pci_addr, size_t pci_size, struct pci_epc_map *map)
> +{
> + int ret;
> +
> + if (!pci_epc_function_is_valid(epc, func_no, vfunc_no))
> + return -EINVAL;
> +
> + if (!pci_size || !map)
> + return -EINVAL;
> +
> + memset(map, 0, sizeof(*map));
> + map->pci_addr = pci_addr;
Since the kdoc says that @map->pci_size might be smaller than the requested size,
I assume that you are only temporarily storing pci_size in map here, and that
map_align() might overwrite this value. Perhaps add a comment here that explains
that map_align() might/will overwrite this value.
> + map->pci_size = pci_size;
> +
> + if (!epc->ops->map_align) {
> + /* Assume that the EP controller has no alignment constraint */
> + map->map_pci_addr = pci_addr;
> + map->map_size = pci_size;
> + map->map_ofst = 0;
> + return 0;
> + }
> +
> + mutex_lock(&epc->lock);
> + ret = epc->ops->map_align(epc, func_no, vfunc_no, map);
> + mutex_unlock(&epc->lock);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(pci_epc_map_align);
> +
> /**
> * pci_epc_map_addr() - map CPU address to PCI address
> * @epc: the EPC device on which address is allocated
> diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h
> index 42ef06136bd1..9df8a83e8d10 100644
> --- a/include/linux/pci-epc.h
> +++ b/include/linux/pci-epc.h
> @@ -32,11 +32,44 @@ pci_epc_interface_string(enum pci_epc_interface_type type)
> }
> }
>
> +/**
> + * struct pci_epc_map - information about EPC memory for mapping a RC PCI
> + * address range
> + * @pci_addr: start address of the RC PCI address range to map
> + * @pci_size: size of the RC PCI address range mapped from @pci_addr
> + * @map_pci_addr: RC PCI address used as the first address mapped (may be lower
> + * than @pci_addr)
> + * @map_size: size of the controller memory needed for mapping the RC PCI address
> + * range @pci_addr..@pci_addr+@pci_size
> + * @map_ofst: offset into the mapped controller memory to access @pci_addr
> + * @phys_base: base physical address of the allocated EPC memory for mapping the
> + * RC PCI address range
> + * @phys_addr: physical address at which @pci_addr is mapped
> + * @virt_base: base virtual address of the allocated EPC memory for mapping the
> + * RC PCI address range
> + * @virt_addr: virtual address at which @pci_addr is mapped
> + */
> +struct pci_epc_map {
> + phys_addr_t pci_addr;
> + size_t pci_size;
> +
> + phys_addr_t map_pci_addr;
> + size_t map_size;
> + phys_addr_t map_ofst;
> +
> + phys_addr_t phys_base;
> + phys_addr_t phys_addr;
> + void __iomem *virt_base;
> + void __iomem *virt_addr;
> +};
> +
> /**
> * struct pci_epc_ops - set of function pointers for performing EPC operations
> * @write_header: ops to populate configuration space header
> * @set_bar: ops to configure the BAR
> * @clear_bar: ops to reset the BAR
> + * @map_align: operation to get the size and offset into a controller memory
> + * window needed to map an RC PCI address region
> * @map_addr: ops to map CPU address to PCI address
> * @unmap_addr: ops to unmap CPU address and PCI address
> * @set_msi: ops to set the requested number of MSI interrupts in the MSI
> @@ -61,6 +94,8 @@ struct pci_epc_ops {
> struct pci_epf_bar *epf_bar);
> void (*clear_bar)(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> struct pci_epf_bar *epf_bar);
> + int (*map_align)(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> + struct pci_epc_map *map);
> int (*map_addr)(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> phys_addr_t addr, u64 pci_addr, size_t size);
> void (*unmap_addr)(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> @@ -241,6 +276,8 @@ int pci_epc_set_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> struct pci_epf_bar *epf_bar);
> void pci_epc_clear_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> struct pci_epf_bar *epf_bar);
> +int pci_epc_map_align(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> + u64 pci_addr, size_t size, struct pci_epc_map *map);
> int pci_epc_map_addr(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> phys_addr_t phys_addr,
> u64 pci_addr, size_t size);
> --
> 2.46.2
>
Reviewed-by: Niklas Cassel <cassel@xxxxxxxxxx>
