[PATCH v21 5/9] PCI: endpoint: Add pci_epf_align_inbound_addr() helper for address alignment

[Frank Li via B4 Relay <devnull+Frank.Li.nxp.com@kernel.org>]

From: Frank Li <Frank.Li@nxp.com>

Introduce the helper function pci_epf_align_inbound_addr() to adjust
addresses according to PCI BAR alignment requirements, converting addresses
into base and offset values.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
Changes in v21
- align to bar size

Changes in V20
- update function kdoc comments.
- 128 come from pci_epf_alloc_space() drivers/pci/endpoint/pci-epf-core.c

Change from v15 to v16
- none

Change from v14 to v15
- change out address type to dma_addr_t to fix below build issue

| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202502082311.G1hWGggF-lkp@intel.com/

All errors (new ones prefixed by >>):

   drivers/pci/endpoint/functions/pci-epf-test.c: In function 'pci_epf_test_enable_doorbell':
>> drivers/pci/endpoint/functions/pci-epf-test.c:726:42: error: passing argument 4 of 'pci_epf_align_inbound_addr' from incompatible pointer type [-Werror=incompatible-pointer-types]
     726 |                                          &epf_test->db_bar.phys_addr, &offset);
         |                                          ^~~~~~~~~~~~~~~~~~~~~~~~~~~
         |                                          |
         |                                          dma_addr_t * {aka unsigned int *}
   In file included from include/linux/pci-epc.h:12,

Change form v9 to v14
- none

change from v8 to v9
- pci_epf_align_inbound_addr(), base and off must be not NULL
- rm pci_epf_align_inbound_addr_lo_hi()

change from v7 to v8
- change name to pci_epf_align_inbound_addr()
- update comment said only need for memory, which not allocated by
pci_epf_alloc_space().

change from v6 to v7
- new patch
---
 drivers/pci/endpoint/pci-epf-core.c | 36 ++++++++++++++++++++++++++++++++++++
 include/linux/pci-epf.h             |  3 +++
 2 files changed, 39 insertions(+)

diff --git a/drivers/pci/endpoint/pci-epf-core.c b/drivers/pci/endpoint/pci-epf-core.c
index 577a9e490115c9dd5d7fb624c4a3001f39b97e78..2947ca52edbe8834f09313249ad3871bc7a462b1 100644
--- a/drivers/pci/endpoint/pci-epf-core.c
+++ b/drivers/pci/endpoint/pci-epf-core.c
@@ -477,6 +477,42 @@ struct pci_epf *pci_epf_create(const char *name)
 }
 EXPORT_SYMBOL_GPL(pci_epf_create);
 
+/**
+ * pci_epf_align_inbound_addr() - Align the given address based on the BAR
+ *				  alignment requirement
+ * @epf: the EPF device
+ * @addr: inbound address to be aligned
+ * @bar: the BAR number corresponding to the given addr
+ * @base: base address matching the @bar alignment requirement.
+ * @off: offset to be added to the @base address.
+ *
+ * Helper function to align input 'addr' to base and offset, which match
+ * BAR's alignment requirement.
+ *
+ * The pci_epf_alloc_space() function already accounts for alignment. This is
+ * primarily intended for use with other memory regions not allocated by
+ * pci_epf_alloc_space(), such as peripheral register spaces or the trigger
+ * address for a platform MSI controller.
+ */
+int pci_epf_align_inbound_addr(struct pci_epf *epf, enum pci_barno bar,
+			       u64 addr, dma_addr_t *base, size_t *off)
+{
+	/*
+	 * Most EP controllers require the BAR start address to be aligned to
+	 * the BAR size, because they mask off the lower bits.
+	 *
+	 * Alignment to BAR size also works for controllers that support
+	 * unaligned addresses.
+	 */
+	u64 align = epf->bar[bar].size;
+
+	*base = round_down(addr, align);
+	*off = addr & (align - 1);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pci_epf_align_inbound_addr);
+
 static void pci_epf_dev_release(struct device *dev)
 {
 	struct pci_epf *epf = to_pci_epf(dev);
diff --git a/include/linux/pci-epf.h b/include/linux/pci-epf.h
index a3b1a1d90d18356e8cda966c7004c3be93962a0d..0ca08f0d05d7439ef4043a77c204062989a27bd9 100644
--- a/include/linux/pci-epf.h
+++ b/include/linux/pci-epf.h
@@ -241,6 +241,9 @@ void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar,
 			  enum pci_epc_interface_type type);
 void pci_epf_free_space(struct pci_epf *epf, void *addr, enum pci_barno bar,
 			enum pci_epc_interface_type type);
+
+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);
 void pci_epf_unbind(struct pci_epf *epf);
 int pci_epf_add_vepf(struct pci_epf *epf_pf, struct pci_epf *epf_vf);

-- 
2.34.1