Add three registers: doorbell_bar, doorbell_addr, and doorbell_data,
along with doorbell_done. 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 doorbell_done in the doorbell callback to indicate completion.

To avoid broken compatibility, 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 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 | 117 ++++++++++++++++++++++++++
 1 file changed, 117 insertions(+)

diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
index ef6677f34116e..6077a51bbd7c4 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 +654,63 @@ static void pci_epf_test_raise_irq(struct pci_epf_test *epf_test,
 	}
 }
 
+static void pci_epf_enable_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;
+	struct pci_epf_bar db_bar;
+	struct msi_msg *msg;
+	size_t offset;
+	int ret;
+
+	if (bar < BAR_0 || bar == epf_test->test_reg_bar || !epf->db_msg) {
+		reg->status |= STATUS_DOORBELL_ENABLE_FAIL;
+		return;
+	}
+
+	msg = &epf->db_msg[0].msg;
+	ret = pci_epf_align_addr_lo_hi(epf, bar, msg->address_lo, msg->address_hi,
+				       &db_bar.phys_addr, &offset);
+
+	if (ret) {
+		reg->status |= STATUS_DOORBELL_ENABLE_FAIL;
+		return;
+	}
+
+	reg->doorbell_offset = offset;
+
+	db_bar.barno = bar;
+	db_bar.size = epf->bar[bar].size;
+	db_bar.flags = epf->bar[bar].flags;
+	db_bar.addr = NULL;
+
+	ret = pci_epc_set_bar(epc, epf->func_no, epf->vfunc_no, &db_bar);
+	if (!ret)
+		reg->status |= STATUS_DOORBELL_ENABLE_SUCCESS;
+	else
+		reg->status |= STATUS_DOORBELL_ENABLE_FAIL;
+}
+
+static void pci_epf_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;
+}
+
 static void pci_epf_test_cmd_handler(struct work_struct *work)
 {
 	u32 command;
@@ -688,6 +757,14 @@ 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_enable_doorbell(epf_test, reg);
+		pci_epf_test_raise_irq(epf_test, reg);
+		break;
+	case COMMAND_DISABLE_DOORBELL:
+		pci_epf_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;
@@ -822,6 +899,18 @@ static int pci_epf_test_link_down(struct pci_epf *epf)
 	return 0;
 }
 
+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 const struct pci_epc_event_ops pci_epf_test_event_ops = {
 	.epc_init = pci_epf_test_epc_init,
 	.epc_deinit = pci_epf_test_epc_deinit,
@@ -921,12 +1010,34 @@ static int pci_epf_test_bind(struct pci_epf *epf)
 	if (ret)
 		return ret;
 
+	ret = pci_epf_alloc_doorbell(epf, 1);
+	if (!ret) {
+		struct pci_epf_test_reg *reg = epf_test->reg[test_reg_bar];
+		struct msi_msg *msg = &epf->db_msg[0].msg;
+		enum pci_barno bar;
+
+		bar = pci_epc_get_next_free_bar(epc_features, test_reg_bar + 1);
+
+		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);
+			return 0;
+		}
+
+		reg->doorbell_data = msg->data;
+		reg->doorbell_bar = bar;
+	}
+
 	return 0;
 }
 
 static void pci_epf_test_unbind(struct pci_epf *epf)
 {
 	struct pci_epf_test *epf_test = epf_get_drvdata(epf);
+	struct pci_epf_test_reg *reg = epf_test->reg[epf_test->test_reg_bar];
 	struct pci_epc *epc = epf->epc;
 
 	cancel_delayed_work_sync(&epf_test->cmd_handler);
@@ -934,6 +1045,12 @@ static void pci_epf_test_unbind(struct pci_epf *epf)
 		pci_epf_test_clean_dma_chan(epf_test);
 		pci_epf_test_clear_bar(epf);
 	}
+
+	if (reg->doorbell_bar > 0) {
+		free_irq(epf->db_msg[0].virq, epf_test);
+		pci_epf_free_doorbell(epf);
+	}
+
 	pci_epf_test_free_space(epf);
 }
 

-- 
2.34.1