[PATCH v5 3/4] PCI: endpoint: Add API pci_epf_assign_bar_space()

Frank Li
2025-10-09T20:55:06Z

Add pci_epf_assign_bar_space() to allow setting any physical address as
inbound memory space, such as an MSI message base address.

Since PCI BAR size must be a power of two, the input MMIO range
[inbound_addr, inbound_addr + size) is mapped by finding n such that
[base, base + 2^n) covers the range. The base address is also required
to be aligned to 2^n.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
change in v5
- use bar_addr in head file to align function define

change in v4
- use size for bar size.

chagne in v3.
- update function name to pci_epf_assign_bar_space()
- s/allocated/assigned/
- add check when align down input address to memory align require, may not
bar's size can't cover required ragion.

change in v2
- add new API pci_epf_set_inbound_space()
- fix bits 8 * size_of(dma_addr_t);
---
drivers/pci/endpoint/pci-epf-core.c | 80 +++++++++++++++++++++++++++++++++++++
include/linux/pci-epf.h | 6 +++
2 files changed, 86 insertions(+)

diff --git a/drivers/pci/endpoint/pci-epf-core.c b/drivers/pci/endpoint/pci-epf-core.c
index 38c4fd06e9693ceaa0c86f67090faa6e390425e1..1c64d69556e6c7c4841ef8a60866515a1f68333b 100644
--- a/drivers/pci/endpoint/pci-epf-core.c
+++ b/drivers/pci/endpoint/pci-epf-core.c
@@ -347,6 +347,86 @@ void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar,
}
EXPORT_SYMBOL_GPL(pci_epf_alloc_space);

+/**
+ * pci_epf_assign_bar_space() - Assign PCI EPF BAR space
+ * @epf: the EPF device to whom allocate the memory
+ * @size: the size of the memory that has to be assigned
+ * @bar: the BAR number corresponding to the assigned register space
+ * @epc_features: the features provided by the EPC specific to this EPF
+ * @type: Identifies if the assignment is for primary EPC or secondary EPC
+ * @bar_addr: Address to be assigned for the @bar
+ *
+ * Invoke to assigned memory for the PCI EPF register space.
+ * Flag PCI_BASE_ADDRESS_MEM_TYPE_64 will automatically get set if the BAR
+ * can only be a 64-bit BAR, or if the requested size is larger than 2 GB.
+ */
+int pci_epf_assign_bar_space(struct pci_epf *epf, size_t size,
+ enum pci_barno bar,
+ const struct pci_epc_features *epc_features,
+ enum pci_epc_interface_type type,
+ dma_addr_t bar_addr)
+{
+ size_t bar_size, aligned_mem_size;
+ struct pci_epf_bar *epf_bar;
+ struct pci_epc *epc;
+ dma_addr_t limit;
+ int pos;
+
+ if (!size)
+ return -EINVAL;
+
+ limit = bar_addr + size - 1;
+
+ /*
+ * Bits: 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
+ * bar_addr: U U U U U U 0 X X X X X X X X X
+ * limit: U U U U U U 1 X X X X X X X X X
+ *
+ * U means address bits have not change in Range [bar_addr, limit]
+ * X means bit 0 or 1.
+ *
+ * bar_addr^limit 0 0 0 0 0 0 1 X X X X X X X X X
+ * Find first bit 1 pos from MSB, 2 ^ pos windows will cover
+ * [bar_Addr, limit] range.
+ */
+ for (pos = 8 * sizeof(dma_addr_t) - 1; pos > 0; pos--)
+ if ((limit ^ bar_addr) & BIT_ULL(pos))
+ break;
+
+ if (pos == 8 * sizeof(dma_addr_t) - 1)
+ return -EINVAL;
+
+ bar_size = BIT_ULL(pos + 1);
+ if (pci_epf_get_bar_required_size(epf, &bar_size, &aligned_mem_size,
+ bar, epc_features, type))
+ return -ENOMEM;
+
+ if (type == PRIMARY_INTERFACE) {
+ epc = epf->epc;
+ epf_bar = epf->bar;
+ } else {
+ epc = epf->sec_epc;
+ epf_bar = epf->sec_epc_bar;
+ }
+
+ epf_bar[bar].phys_addr = ALIGN_DOWN(bar_addr, aligned_mem_size);
+
+ if (epf_bar[bar].phys_addr + bar_size < limit)
+ return -ENOMEM;
+
+ epf_bar[bar].addr = NULL;
+ epf_bar[bar].size = bar_size;
+ epf_bar[bar].mem_size = aligned_mem_size;
+ 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;
+ else
+ epf_bar[bar].flags |= PCI_BASE_ADDRESS_MEM_TYPE_32;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(pci_epf_assign_bar_space);
+
static void pci_epf_remove_cfs(struct pci_epf_driver *driver)
{
struct config_group *group, *tmp;
diff --git a/include/linux/pci-epf.h b/include/linux/pci-epf.h
index 4022dd080e20f2959f3a5faf4cfe054ddb5856a7..48f68c4dcfa5e2e3bb97963c6b0f47effe87f53b 100644
--- a/include/linux/pci-epf.h
+++ b/include/linux/pci-epf.h
@@ -242,6 +242,12 @@ void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar,
void pci_epf_free_space(struct pci_epf *epf, void *addr, enum pci_barno bar,
enum pci_epc_interface_type type);

+int pci_epf_assign_bar_space(struct pci_epf *epf, size_t size,
+ enum pci_barno bar,
+ const struct pci_epc_features *epc_features,
+ enum pci_epc_interface_type type,
+ dma_addr_t bar_addr);
+
int pci_epf_align_inbound_addr(struct pci_epf *epf, enum pci_barno bar,
u64 addr, dma_addr_t *base, size_t *off);
int pci_epf_bind(struct pci_epf *epf);

--
2.34.1