PCI: rockchip-ep: Implement the pci_epc_ops::align_addr() operation

The Rockchip PCIe endpoint controller handles PCIe transfers addresses
by masking the lower bits of the programmed PCI address and using the
same number of lower bits from the CPU address space used for the
mapping. For a PCI mapping of size bytes starting from pci_addr, the
number of bits masked is the number of address bits changing in the
address range [pci_addr..pci_addr + size - 1], up to 20 bits, that is,
up to 1MB mappings.

This means that when preparing a PCI address mapping, an endpoint
function driver must use an offset into the allocated controller
memory region that is equal to the mask of the starting PCI address
over rockchip_pcie_ep_ob_atu_num_bits() bits. This offset also
determines the maximum size of the mapping given the starting PCI
address and the fixed 1MB controller memory window size.

Implement the ->align_addr() endpoint controller operation to allow the
mapping alignment to be transparently handled by endpoint function
drivers through the function pci_epc_mem_map().

Link: https://lore.kernel.org/r/20241017015849.190271-6-dlemoal@kernel.org
Co-developed-by: Rick Wertenbroek <rick.wertenbroek@gmail.com>
Signed-off-by: Rick Wertenbroek <rick.wertenbroek@gmail.com>
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
[kwilczynski: change local variable name for address offset]
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

Author: damien-lemoal

drivers/pci/controller/pcie-rockchip-ep.c

@@ -238,6 +238,28 @@ static inline u32 rockchip_ob_region(phys_addr_t addr)
 	return (addr >> ilog2(SZ_1M)) & 0x1f;
 }
 
+static u64 rockchip_pcie_ep_align_addr(struct pci_epc *epc, u64 pci_addr,
+				       size_t *pci_size, size_t *addr_offset)
+{
+	struct rockchip_pcie_ep *ep = epc_get_drvdata(epc);
+	size_t size = *pci_size;
+	u64 offset, mask;
+	int num_bits;
+
+	num_bits = rockchip_pcie_ep_ob_atu_num_bits(&ep->rockchip,
+						    pci_addr, size);
+	mask = (1ULL << num_bits) - 1;
+
+	offset = pci_addr & mask;
+	if (size + offset > SZ_1M)
+		size = SZ_1M - offset;
+
+	*pci_size = ALIGN(offset + size, ROCKCHIP_PCIE_AT_SIZE_ALIGN);
+	*addr_offset = offset;
+
+	return pci_addr & ~mask;
+}
+
 static int rockchip_pcie_ep_map_addr(struct pci_epc *epc, u8 fn, u8 vfn,
 				     phys_addr_t addr, u64 pci_addr,
 				     size_t size)
@@ -461,6 +483,7 @@ static const struct pci_epc_ops rockchip_pcie_epc_ops = {
 	.write_header	= rockchip_pcie_ep_write_header,
 	.set_bar	= rockchip_pcie_ep_set_bar,
 	.clear_bar	= rockchip_pcie_ep_clear_bar,
+	.align_addr	= rockchip_pcie_ep_align_addr,
 	.map_addr	= rockchip_pcie_ep_map_addr,
 	.unmap_addr	= rockchip_pcie_ep_unmap_addr,
 	.set_msi	= rockchip_pcie_ep_set_msi,

drivers/pci/controller/pcie-rockchip.h

@@ -241,6 +241,11 @@
 #define   ROCKCHIP_PCIE_EP_MSIX_CAP_CP_MASK		GENMASK(15, 8)
 #define ROCKCHIP_PCIE_EP_DUMMY_IRQ_ADDR				0x1
 #define ROCKCHIP_PCIE_EP_PCI_LEGACY_IRQ_ADDR		0x3
+
+#define ROCKCHIP_PCIE_AT_MIN_NUM_BITS	8
+#define ROCKCHIP_PCIE_AT_MAX_NUM_BITS	20
+#define ROCKCHIP_PCIE_AT_SIZE_ALIGN	(1UL << ROCKCHIP_PCIE_AT_MIN_NUM_BITS)
+
 #define ROCKCHIP_PCIE_EP_FUNC_BASE(fn) \
 	(PCIE_EP_PF_CONFIG_REGS_BASE + (((fn) << 12) & GENMASK(19, 12)))
 #define ROCKCHIP_PCIE_EP_VIRT_FUNC_BASE(fn) \