[PATCH v5 2/4] PCI: endpoint: Add helper function pci_epf_get_bar_required_size()

Frank Li
2025-10-09T20:55:04Z

Introduce pci_epf_get_bar_required_size() to retrieve the required BAR
size and memory size. Prepare for adding support to set an MMIO address to
a specific BAR.

Use two variables 'size' and 'aligned_mem_size' to avoid confuse.

No functional changes.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
change in v5
- update commit message.

change in v4
- use size_t *bar_size as in/out arugment.

change in v3
- change return value to int.
- use two pointers return bar size aligned and memory start address aligned
- update comments about why need memory align size. Actually iATU require
start address match aligned requirement. Since kernel return align to
size's address.
- use two varible aligned_bar_size and aligned_mem_size to avoid confuse
use 'size'.

change in v2
- new patch
---
drivers/pci/endpoint/pci-epf-core.c | 75 +++++++++++++++++++++++--------------
1 file changed, 47 insertions(+), 28 deletions(-)

diff --git a/drivers/pci/endpoint/pci-epf-core.c b/drivers/pci/endpoint/pci-epf-core.c
index 214e3f6e6d0d5a216c3469b8ff47908414cd1286..38c4fd06e9693ceaa0c86f67090faa6e390425e1 100644
--- a/drivers/pci/endpoint/pci-epf-core.c
+++ b/drivers/pci/endpoint/pci-epf-core.c
@@ -208,6 +208,49 @@ void pci_epf_remove_vepf(struct pci_epf *epf_pf, struct pci_epf *epf_vf)
}
EXPORT_SYMBOL_GPL(pci_epf_remove_vepf);

+static int
+pci_epf_get_bar_required_size(struct pci_epf *epf, size_t *bar_size,
+ size_t *aligned_mem_size,
+ enum pci_barno bar,
+ const struct pci_epc_features *epc_features,
+ enum pci_epc_interface_type type)
+{
+ u64 bar_fixed_size = epc_features->bar[bar].fixed_size;
+ size_t align = epc_features->align;
+ size_t size = *bar_size;
+
+ if (size < 128)
+ size = 128;
+
+ /* According to PCIe base spec, min size for a resizable BAR is 1 MB. */
+ if (epc_features->bar[bar].type == BAR_RESIZABLE && size < SZ_1M)
+ size = SZ_1M;
+
+ if (epc_features->bar[bar].type == BAR_FIXED && bar_fixed_size) {
+ if (size > bar_fixed_size) {
+ dev_err(&epf->dev,
+ "requested BAR size is larger than fixed size\n");
+ return -ENOMEM;
+ }
+ size = bar_fixed_size;
+ } else {
+ /* BAR size must be power of two */
+ size = roundup_pow_of_two(size);
+ }
+
+ *bar_size = size;
+
+ /*
+ * The EPC's BAR start address must meet alignment requirements. In most
+ * cases, the alignment will match the BAR size. However, differences
+ * can occur—for example, when the fixed BAR size (e.g., 128 bytes) is
+ * smaller than the required alignment (e.g., 4 KB).
+ */
+ *aligned_mem_size = align ? ALIGN(size, align) : size;
+
+ return 0;
+}
+
/**
* pci_epf_free_space() - free the allocated PCI EPF register space
* @epf: the EPF device from whom to free the memory
@@ -264,40 +307,16 @@ void *pci_epf_alloc_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)
{
- u64 bar_fixed_size = epc_features->bar[bar].fixed_size;
- size_t mem_size, align = epc_features->align;
struct pci_epf_bar *epf_bar;
dma_addr_t phys_addr;
struct pci_epc *epc;
struct device *dev;
+ size_t mem_size;
void *space;

- if (size < 128)
- size = 128;
-
- /* According to PCIe base spec, min size for a resizable BAR is 1 MB. */
- if (epc_features->bar[bar].type == BAR_RESIZABLE && size < SZ_1M)
- size = SZ_1M;
-
- if (epc_features->bar[bar].type == BAR_FIXED && bar_fixed_size) {
- if (size > bar_fixed_size) {
- dev_err(&epf->dev,
- "requested BAR size is larger than fixed size\n");
- return NULL;
- }
- size = bar_fixed_size;
- } else {
- /* BAR size must be power of two */
- size = roundup_pow_of_two(size);
- }
-
- /*
- * Allocate enough memory to accommodate the iATU alignment
- * requirement. In most cases, this will be the same as .size but
- * it might be different if, for example, the fixed size of a BAR
- * is smaller than align.
- */
- mem_size = align ? ALIGN(size, align) : size;
+ if (pci_epf_get_bar_required_size(epf, &size, &mem_size, bar,
+ epc_features, type))
+ return NULL;

if (type == PRIMARY_INTERFACE) {
epc = epf->epc;

--
2.34.1