[PATCH 4/5] PCI: endpoint: Add D_STATE notifier support

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

Add support to notify the EPF device about the Device State (D_STATE)
event received by the EPC device from the Root complex.

Usage:
======

EPC
---

```
static irqreturn_t pcie_ep_irq(int irq, void *data)
{
...
	case PCIE_EP_INT_D_STATE:
		dstate = dw_pcie_readl_dbi(pci, DBI_CON_STATUS) & 0x3;
		pci_epc_d_state_notify(epc, dstate);
		break;
...
}
```

EPF
---

```
static int pci_epf_notifier(struct notifier_block *nb, unsigned long val,
			    void *data)
{
...
	case D_STATE:
		dstate = data;
		if (dstate == PCIE_EP_D0)
			/* Handle D0 event */
		else if (dstate == PCIE_EP_D3)
			/* Handle D3 event */
		break;
...
}
```

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
---
 drivers/pci/endpoint/pci-epc-core.c | 18 ++++++++++++++++++
 include/linux/pci-epc.h             |  1 +
 include/linux/pci-epf.h             |  1 +
 3 files changed, 20 insertions(+)

diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
index 63fe90dbbba2..b4a7bb3caa97 100644
--- a/drivers/pci/endpoint/pci-epc-core.c
+++ b/drivers/pci/endpoint/pci-epc-core.c
@@ -710,6 +710,24 @@ void pci_epc_pme_notify(struct pci_epc *epc, void *data)
 }
 EXPORT_SYMBOL_GPL(pci_epc_pme_notify);
 
+/**
+ * pci_epc_d_state_notify() - Notify the EPF device that the EPC device has
+ *			      received the Device State event from Root complex
+ * @epc: the EPC device that received the Device State event
+ * @data: Data for the D_STATE notifier
+ *
+ * Invoke to notify the EPF device that the EPC device has received the Device
+ * State (D_STATE) event from the Root complex
+ */
+void pci_epc_d_state_notify(struct pci_epc *epc, void *data)
+{
+	if (!epc || IS_ERR(epc))
+		return;
+
+	atomic_notifier_call_chain(&epc->notifier, D_STATE, data);
+}
+EXPORT_SYMBOL_GPL(pci_epc_d_state_notify);
+
 /**
  * pci_epc_destroy() - destroy the EPC device
  * @epc: the EPC device that has to be destroyed
diff --git a/include/linux/pci-epc.h b/include/linux/pci-epc.h
index 37dbcade1780..94c66fae8a88 100644
--- a/include/linux/pci-epc.h
+++ b/include/linux/pci-epc.h
@@ -206,6 +206,7 @@ void pci_epc_linkdown(struct pci_epc *epc);
 void pci_epc_init_notify(struct pci_epc *epc);
 void pci_epc_bme_notify(struct pci_epc *epc);
 void pci_epc_pme_notify(struct pci_epc *epc, void *data);
+void pci_epc_d_state_notify(struct pci_epc *epc, void *data);
 void pci_epc_remove_epf(struct pci_epc *epc, struct pci_epf *epf,
 			enum pci_epc_interface_type type);
 int pci_epc_write_header(struct pci_epc *epc, u8 func_no,
diff --git a/include/linux/pci-epf.h b/include/linux/pci-epf.h
index c162a73eb836..ca020c080431 100644
--- a/include/linux/pci-epf.h
+++ b/include/linux/pci-epf.h
@@ -23,6 +23,7 @@ enum pci_notify_event {
 	LINK_DOWN,
 	BME,
 	PME,
+	D_STATE,
 };
 
 enum pci_barno {
-- 
2.25.1