PCI: endpoint: Add support to specify alignment for buffers allocated to BARs

The address that is allocated using pci_epf_alloc_space() is
directly written to the target address of the Inbound Address
Translation unit (ie the HW component implementing inbound address
decoding) on endpoint controllers.

Designware IP [1] has a configuration parameter (CX_ATU_MIN_REGION_SIZE
[2]) which has 64KB as default value and the lower 16 bits of the Base,
Limit and Target registers of the Inbound ATU are fixed to zero. If the
programmed memory address is not aligned to 64 KB boundary this causes
memory corruption.

Modify pci_epf_alloc_space() API to take alignment size as argument in
order to allocate buffers to be mapped to BARs with an alignment that
suits the platform where they are used.

Add an 'align' parameter to epc_features which can be used by platform
drivers to specify the BAR allocation alignment requirements and use
this while invoking pci_epf_alloc_space().

[1] "I/O and MEM Match Modes" section in DesignWare Cores PCI Express
Controller Databook version 4.90a
[2] http://www.ti.com/lit/ug/spruid7c/spruid7c.pdf

Signed-off-by: Kishon Vijay Abraham I <[e-mail]>
Signed-off-by: Lorenzo Pieralisi <[e-mail]>

drivers/pci/endpoint/functions/pci-epf-test.c

···
 	epc_features = epf_test->epc_features;
 
 	base = pci_epf_alloc_space(epf, sizeof(struct pci_epf_test_reg),
-				   test_reg_bar);
+				   test_reg_bar, epc_features->align);
 	if (!base) {
 		dev_err(dev, "Failed to allocated register space\n");
 		return -ENOMEM;
···
 		if (!!(epc_features->reserved_bar & (1 << bar)))
 			continue;
 
-		base = pci_epf_alloc_space(epf, bar_size[bar], bar);
+		base = pci_epf_alloc_space(epf, bar_size[bar], bar,
+					   epc_features->align);
 		if (!base)
 			dev_err(dev, "Failed to allocate space for BAR%d\n",
 				bar);

drivers/pci/endpoint/pci-epf-core.c

···
  * pci_epf_alloc_space() - allocate memory for the PCI EPF register space
  * @size: the size of the memory that has to be allocated
  * @bar: the BAR number corresponding to the allocated register space
+ * @align: alignment size for the allocation region
  *
  * Invoke to allocate memory for the PCI EPF register space.
  */
-void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar)
+void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar,
+			  size_t align)
 {
 	void *space;
 	struct device *dev = epf->epc->dev.parent;
···
 
 	if (size < 128)
 		size = 128;
-	size = roundup_pow_of_two(size);
+
+	if (align)
+		size = ALIGN(size, align);
+	else
+		size = roundup_pow_of_two(size);
 
 	space = dma_alloc_coherent(dev, size, &phys_addr, GFP_KERNEL);
 	if (!space) {

include/linux/pci-epc.h

···
  * @reserved_bar: bitmap to indicate reserved BAR unavailable to function driver
  * @bar_fixed_64bit: bitmap to indicate fixed 64bit BARs
  * @bar_fixed_size: Array specifying the size supported by each BAR
+ * @align: alignment size required for BAR buffer allocation
  */
 struct pci_epc_features {
 	unsigned int	linkup_notifier : 1;
···
 	u8	reserved_bar;
 	u8	bar_fixed_64bit;
 	u64	bar_fixed_size[BAR_5 + 1];
+	size_t	align;
 };
 
 #define to_pci_epc(device) container_of((device), struct pci_epc, dev)

include/linux/pci-epf.h

···
 int __pci_epf_register_driver(struct pci_epf_driver *driver,
 			      struct module *owner);
 void pci_epf_unregister_driver(struct pci_epf_driver *driver);
-void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar);
+void *pci_epf_alloc_space(struct pci_epf *epf, size_t size, enum pci_barno bar,
+			  size_t align);
 void pci_epf_free_space(struct pci_epf *epf, void *addr, enum pci_barno bar);
 int pci_epf_bind(struct pci_epf *epf);
 void pci_epf_unbind(struct pci_epf *epf);