[PATCH 1/2] PCI: endpoint: Introduce 'get_bar' to map fixed address BARs in EPC

[Rick Wertenbroek <rick.wertenbroek@gmail.com>]

The current mechanism for BARs is as follows: The endpoint function
allocates memory with 'pci_epf_alloc_space' which calls
'dma_alloc_coherent' to allocate memory for the BAR and fills a
'pci_epf_bar' structure with the physical address, virtual address,
size, BAR number and flags. This 'pci_epf_bar' structure is passed
to the endpoint controller driver through 'set_bar'. The endpoint
controller driver configures the actual endpoint to reroute PCI
read/write TLPs to the BAR memory space allocated.

The problem with this is that not all PCI endpoint controllers can
be configured to reroute read/write TLPs to their BAR to a given
address in memory space. Some PCI endpoint controllers e.g., FPGA
IPs for Intel/Altera and AMD/Xilinx PCI endpoints. These controllers
come with pre-assigned memory for the BARs (e.g., in FPGA BRAM),
because of this the endpoint controller driver has no way to tell
these controllers to reroute the read/write TLPs to the memory
allocated by 'pci_epf_alloc_space' and no way to get access to the
memory pre-assigned to the BARs through the current API.

Therefore, introduce 'get_bar' which allows to get access to a BAR
without calling 'pci_epf_alloc_space'. Controllers with pre-assigned
bars can therefore implement 'get_bar' which will assign the BAR
pyhsical address, virtual address through ioremap, size, and flags.

PCI endpoint functions can query the endpoint controller through the
'fixed_addr' boolean in the 'pci_epc_bar_desc' structure. Similarly
to the BAR type, fixed size or fixed 64-bit descriptions. With this
information they can either call 'pci_epf_alloc_space' and 'set_bar'
as is currently the case, or call the new 'get_bar'. Both will provide
a working, memory mapped BAR, that can be used in the endpoint
function.

Signed-off-by: Rick Wertenbroek <rick.wertenbroek@gmail.com>
---
 drivers/pci/endpoint/pci-epc-core.c | 37 +++++++++++++++++++++++++++++
 include/linux/pci-epc.h             |  7 ++++++
 2 files changed, 44 insertions(+)

diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
index 84309dfe0c68..fcef848876fe 100644
--- a/drivers/pci/endpoint/pci-epc-core.c
+++ b/drivers/pci/endpoint/pci-epc-core.c
@@ -544,6 +544,43 @@ int pci_epc_set_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
 }
 EXPORT_SYMBOL_GPL(pci_epc_set_bar);
 
+/**
+ * pci_epc_get_bar - get BAR configuration from a fixed address BAR
+ * @epc: the EPC device on which BAR resides
+ * @func_no: the physical endpoint function number in the EPC device
+ * @vfunc_no: the virtual endpoint function number in the physical function
+ * @bar: the BAR number to get
+ * @epf_bar: the struct epf_bar to fill
+ *
+ * Invoke to get the configuration of the endpoint device fixed address BAR
+ */
+int pci_epc_get_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
+		    enum pci_barno bar, struct pci_epf_bar *epf_bar)
+{
+	int ret;
+
+	if (IS_ERR_OR_NULL(epc) || func_no >= epc->max_functions)
+		return -EINVAL;
+
+	if (vfunc_no > 0 && (!epc->max_vfs || vfunc_no > epc->max_vfs[func_no]))
+		return -EINVAL;
+
+	if (bar < 0 || bar >= PCI_STD_NUM_BARS)
+		return -EINVAL;
+
+	if (!epc->ops->get_bar)
+		return -EINVAL;
+
+	epf_bar->barno = bar;
+
+	mutex_lock(&epc->lock);
+	ret = epc->ops->get_bar(epc, func_no, vfunc_no, bar, epf_bar);
+	mutex_unlock(&epc->lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pci_epc_get_bar);
+
 /**
  * pci_epc_write_header() - write standard configuration header
  * @epc: the EPC device to which the configuration header should be written
diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h
index 85bdf2adb760..a5ea50dd49ba 100644
--- a/include/linux/pci-epc.h
+++ b/include/linux/pci-epc.h
@@ -37,6 +37,7 @@ pci_epc_interface_string(enum pci_epc_interface_type type)
  * @write_header: ops to populate configuration space header
  * @set_bar: ops to configure the BAR
  * @clear_bar: ops to reset the BAR
+ * @get_bar: ops to get a fixed address BAR that cannot be set/cleared
  * @map_addr: ops to map CPU address to PCI address
  * @unmap_addr: ops to unmap CPU address and PCI address
  * @set_msi: ops to set the requested number of MSI interrupts in the MSI
@@ -61,6 +62,8 @@ struct pci_epc_ops {
 			   struct pci_epf_bar *epf_bar);
 	void	(*clear_bar)(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
 			     struct pci_epf_bar *epf_bar);
+	int	(*get_bar)(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
+			   enum pci_barno, struct pci_epf_bar *epf_bar);
 	int	(*map_addr)(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
 			    phys_addr_t addr, u64 pci_addr, size_t size);
 	void	(*unmap_addr)(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
@@ -163,6 +166,7 @@ enum pci_epc_bar_type {
  * struct pci_epc_bar_desc - hardware description for a BAR
  * @type: the type of the BAR
  * @fixed_size: the fixed size, only applicable if type is BAR_FIXED_MASK.
+ * @fixed_addr: indicates that the BAR has a fixed address in memory map.
  * @only_64bit: if true, an EPF driver is not allowed to choose if this BAR
  *		should be configured as 32-bit or 64-bit, the EPF driver must
  *		configure this BAR as 64-bit. Additionally, the BAR succeeding
@@ -176,6 +180,7 @@ enum pci_epc_bar_type {
 struct pci_epc_bar_desc {
 	enum pci_epc_bar_type type;
 	u64 fixed_size;
+	bool fixed_addr;
 	bool only_64bit;
 };
 
@@ -238,6 +243,8 @@ int pci_epc_set_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
 		    struct pci_epf_bar *epf_bar);
 void pci_epc_clear_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
 		       struct pci_epf_bar *epf_bar);
+int pci_epc_get_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
+		    enum pci_barno, struct pci_epf_bar *epf_bar);
 int pci_epc_map_addr(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
 		     phys_addr_t phys_addr,
 		     u64 pci_addr, size_t size);
-- 
2.25.1