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Message-Id: <20250925-vntb_msi_doorbell-v3-1-ae0b0c93caae@nxp.com>
Date: Thu, 25 Sep 2025 13:01:47 -0400
From: Frank Li <Frank.Li@....com>
To: Manivannan Sadhasivam <mani@...nel.org>,
Krzysztof Wilczyński <kwilczynski@...nel.org>,
Kishon Vijay Abraham I <kishon@...nel.org>,
Bjorn Helgaas <bhelgaas@...gle.com>, Jon Mason <jdmason@...zu.us>,
Dave Jiang <dave.jiang@...el.com>, Allen Hubbe <allenbh@...il.com>
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
ntb@...ts.linux.dev, imx@...ts.linux.dev, Frank Li <Frank.Li@....com>
Subject: [PATCH v3 1/3] PCI: endpoint: Add helper function
pci_epf_get_bar_required_size()
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 'aligned_bar_size' and 'aligned_mem_size' to avoid
confuse.
No functional changes.
Signed-off-by: Frank Li <Frank.Li@....com>
---
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 | 84 +++++++++++++++++++++++--------------
1 file changed, 53 insertions(+), 31 deletions(-)
diff --git a/drivers/pci/endpoint/pci-epf-core.c b/drivers/pci/endpoint/pci-epf-core.c
index d54e18872aefc07c655c94c104a347328ff7a432..2cd0257831f9885a4381c087ed8f3326f5960966 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 size,
+ size_t *aligned_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;
+
+ 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);
+ }
+
+ *aligned_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 +307,17 @@ 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 aligned_size, align = epc_features->align;
+ size_t aligned_mem_size, aligned_bar_size;
struct pci_epf_bar *epf_bar;
dma_addr_t phys_addr;
struct pci_epc *epc;
struct device *dev;
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.
- */
- aligned_size = align ? ALIGN(size, align) : size;
+ if (pci_epf_get_bar_required_size(epf, size, &aligned_bar_size,
+ &aligned_mem_size, bar,
+ epc_features, type))
+ return NULL;
if (type == PRIMARY_INTERFACE) {
epc = epf->epc;
@@ -308,7 +328,9 @@ 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, aligned_size, &phys_addr, GFP_KERNEL);
+
+ space = dma_alloc_coherent(dev, aligned_mem_size,
+ &phys_addr, GFP_KERNEL);
if (!space) {
dev_err(dev, "failed to allocate mem space\n");
return NULL;
@@ -316,8 +338,8 @@ void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar,
epf_bar[bar].phys_addr = phys_addr;
epf_bar[bar].addr = space;
- epf_bar[bar].size = size;
- epf_bar[bar].aligned_size = aligned_size;
+ epf_bar[bar].size = aligned_bar_size;
+ epf_bar[bar].aligned_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;
--
2.34.1
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