Add three registers: doorbell_bar, doorbell_addr, and doorbell_data. Use
pci_epf_alloc_doorbell() to allocate a doorbell address space.

Enable the Root Complex (RC) side driver to trigger pci-epc-test's doorbell
callback handler by writing doorbell_data to the mapped doorbell_bar's
address space.

Set STATUS_DOORBELL_SUCCESS in the doorbell callback to indicate
completion.

Avoid breaking compatibility between host and endpoint, add new command
COMMAND_ENABLE_DOORBELL and COMMAND_DISABLE_DOORBELL. Host side need send
COMMAND_ENABLE_DOORBELL to map one bar's inbound address to MSI space.
the command COMMAND_DISABLE_DOORBELL to recovery original inbound address
mapping.

	 	Host side new driver	Host side old driver

EP: new driver      S				F
EP: old driver      F				F

S: If EP side support MSI, 'pcitest -B' return success.
   If EP side doesn't support MSI, the same to 'F'.

F: 'pcitest -B' return failure, other case as usual.

Tested-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
Change from v9 to v13
- none

Change from v8 to v9
- move pci_epf_alloc_doorbell() into pci_epf_{enable/disable}_doorbell().
- remove doorbell_done in commit message.
- rename pci_epf_{enable/disable}_doorbell() to
pci_epf_test_{enable/disable}_doorbell() to align corrent code style.

Change from v7 to v8
- rename to pci_epf_align_inbound_addr_lo_hi()

Change from v6 to v7
- use help function pci_epf_align_addr_lo_hi()

Change from v5 to v6
- rename doorbell_addr to doorbell_offset

Chagne from v4 to v5
- Add doorbell free at unbind function.
- Move msi irq handler to here to more complex user case, such as differece
doorbell can use difference handler function.
- Add Niklas's code to handle fixed bar's case. If need add your signed-off
tag or co-developer tag, please let me know.

change from v3 to v4
- remove revid requirement
- Add command COMMAND_ENABLE_DOORBELL and COMMAND_DISABLE_DOORBELL.
- call pci_epc_set_bar() to map inbound address to MSI space only at
COMMAND_ENABLE_DOORBELL.
---
 drivers/pci/endpoint/functions/pci-epf-test.c | 132 ++++++++++++++++++++++++++
 1 file changed, 132 insertions(+)

diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
index ef6677f34116e..a0a0e86a081cb 100644
--- a/drivers/pci/endpoint/functions/pci-epf-test.c
+++ b/drivers/pci/endpoint/functions/pci-epf-test.c
@@ -11,12 +11,14 @@
 #include <linux/dmaengine.h>
 #include <linux/io.h>
 #include <linux/module.h>
+#include <linux/msi.h>
 #include <linux/slab.h>
 #include <linux/pci_ids.h>
 #include <linux/random.h>
 
 #include <linux/pci-epc.h>
 #include <linux/pci-epf.h>
+#include <linux/pci-ep-msi.h>
 #include <linux/pci_regs.h>
 
 #define IRQ_TYPE_INTX			0
@@ -29,6 +31,8 @@
 #define COMMAND_READ			BIT(3)
 #define COMMAND_WRITE			BIT(4)
 #define COMMAND_COPY			BIT(5)
+#define COMMAND_ENABLE_DOORBELL		BIT(6)
+#define COMMAND_DISABLE_DOORBELL	BIT(7)
 
 #define STATUS_READ_SUCCESS		BIT(0)
 #define STATUS_READ_FAIL		BIT(1)
@@ -39,6 +43,11 @@
 #define STATUS_IRQ_RAISED		BIT(6)
 #define STATUS_SRC_ADDR_INVALID		BIT(7)
 #define STATUS_DST_ADDR_INVALID		BIT(8)
+#define STATUS_DOORBELL_SUCCESS		BIT(9)
+#define STATUS_DOORBELL_ENABLE_SUCCESS	BIT(10)
+#define STATUS_DOORBELL_ENABLE_FAIL	BIT(11)
+#define STATUS_DOORBELL_DISABLE_SUCCESS BIT(12)
+#define STATUS_DOORBELL_DISABLE_FAIL	BIT(13)
 
 #define FLAG_USE_DMA			BIT(0)
 
@@ -74,6 +83,9 @@ struct pci_epf_test_reg {
 	u32	irq_type;
 	u32	irq_number;
 	u32	flags;
+	u32	doorbell_bar;
+	u32	doorbell_offset;
+	u32	doorbell_data;
 } __packed;
 
 static struct pci_epf_header test_header = {
@@ -642,6 +654,117 @@ static void pci_epf_test_raise_irq(struct pci_epf_test *epf_test,
 	}
 }
 
+static irqreturn_t pci_epf_test_doorbell_handler(int irq, void *data)
+{
+	struct pci_epf_test *epf_test = data;
+	enum pci_barno test_reg_bar = epf_test->test_reg_bar;
+	struct pci_epf_test_reg *reg = epf_test->reg[test_reg_bar];
+
+	reg->status |= STATUS_DOORBELL_SUCCESS;
+	pci_epf_test_raise_irq(epf_test, reg);
+
+	return IRQ_HANDLED;
+}
+
+static void pci_epf_test_doorbell_cleanup(struct pci_epf_test *epf_test)
+{
+	struct pci_epf_test_reg *reg = epf_test->reg[epf_test->test_reg_bar];
+	struct pci_epf *epf = epf_test->epf;
+
+	if (reg->doorbell_bar > 0) {
+		free_irq(epf->db_msg[0].virq, epf_test);
+		reg->doorbell_bar = NO_BAR;
+	}
+
+	if (epf->db_msg)
+		pci_epf_free_doorbell(epf);
+}
+
+static void pci_epf_test_enable_doorbell(struct pci_epf_test *epf_test,
+					 struct pci_epf_test_reg *reg)
+{
+	struct pci_epf *epf = epf_test->epf;
+	struct pci_epf_bar db_bar = {};
+	struct pci_epc *epc = epf->epc;
+	struct msi_msg *msg;
+	enum pci_barno bar;
+	size_t offset;
+	int ret;
+
+	ret = pci_epf_alloc_doorbell(epf, 1);
+	if (ret) {
+		reg->status |= STATUS_DOORBELL_ENABLE_FAIL;
+		return;
+	}
+
+	msg = &epf->db_msg[0].msg;
+	bar = pci_epc_get_next_free_bar(epf_test->epc_features, epf_test->test_reg_bar + 1);
+	if (bar < BAR_0 || bar == epf_test->test_reg_bar || !epf->db_msg) {
+		reg->status |= STATUS_DOORBELL_ENABLE_FAIL;
+		return;
+	}
+
+	ret = request_irq(epf->db_msg[0].virq, pci_epf_test_doorbell_handler, 0,
+			  "pci-test-doorbell", epf_test);
+	if (ret) {
+		dev_err(&epf->dev,
+			"Failed to request irq %d, doorbell feature is not supported\n",
+			epf->db_msg[0].virq);
+		reg->status |= STATUS_DOORBELL_ENABLE_FAIL;
+		pci_epf_test_doorbell_cleanup(epf_test);
+		return;
+	}
+
+	reg->doorbell_data = msg->data;
+	reg->doorbell_bar = bar;
+
+	msg = &epf->db_msg[0].msg;
+	ret = pci_epf_align_inbound_addr(epf, bar, ((u64)msg->address_hi << 32) | msg->address_lo,
+					 &db_bar.phys_addr, &offset);
+
+	if (ret) {
+		reg->status |= STATUS_DOORBELL_ENABLE_FAIL;
+		pci_epf_test_doorbell_cleanup(epf_test);
+		return;
+	}
+
+	reg->doorbell_offset = offset;
+
+	db_bar.barno = bar;
+	db_bar.size = epf->bar[bar].size;
+	db_bar.flags = epf->bar[bar].flags;
+
+	ret = pci_epc_set_bar(epc, epf->func_no, epf->vfunc_no, &db_bar);
+	if (ret) {
+		reg->status |= STATUS_DOORBELL_ENABLE_FAIL;
+		pci_epf_test_doorbell_cleanup(epf_test);
+	} else {
+		reg->status |= STATUS_DOORBELL_ENABLE_SUCCESS;
+	}
+}
+
+static void pci_epf_test_disable_doorbell(struct pci_epf_test *epf_test,
+					  struct pci_epf_test_reg *reg)
+{
+	enum pci_barno bar = reg->doorbell_bar;
+	struct pci_epf *epf = epf_test->epf;
+	struct pci_epc *epc = epf->epc;
+	int ret;
+
+	if (bar < BAR_0 || bar == epf_test->test_reg_bar || !epf->db_msg) {
+		reg->status |= STATUS_DOORBELL_DISABLE_FAIL;
+		return;
+	}
+
+	ret = pci_epc_set_bar(epc, epf->func_no, epf->vfunc_no, &epf->bar[bar]);
+	if (ret)
+		reg->status |= STATUS_DOORBELL_DISABLE_FAIL;
+	else
+		reg->status |= STATUS_DOORBELL_DISABLE_SUCCESS;
+
+	pci_epf_test_doorbell_cleanup(epf_test);
+}
+
 static void pci_epf_test_cmd_handler(struct work_struct *work)
 {
 	u32 command;
@@ -688,6 +811,14 @@ static void pci_epf_test_cmd_handler(struct work_struct *work)
 		pci_epf_test_copy(epf_test, reg);
 		pci_epf_test_raise_irq(epf_test, reg);
 		break;
+	case COMMAND_ENABLE_DOORBELL:
+		pci_epf_test_enable_doorbell(epf_test, reg);
+		pci_epf_test_raise_irq(epf_test, reg);
+		break;
+	case COMMAND_DISABLE_DOORBELL:
+		pci_epf_test_disable_doorbell(epf_test, reg);
+		pci_epf_test_raise_irq(epf_test, reg);
+		break;
 	default:
 		dev_err(dev, "Invalid command 0x%x\n", command);
 		break;
@@ -934,6 +1065,7 @@ static void pci_epf_test_unbind(struct pci_epf *epf)
 		pci_epf_test_clean_dma_chan(epf_test);
 		pci_epf_test_clear_bar(epf);
 	}
+	pci_epf_test_doorbell_cleanup(epf_test);
 	pci_epf_test_free_space(epf);
 }
 

-- 
2.34.1