[PATCH v14 08/21] PCI: dwc: Add support for triggering INTx IRQs from endpoint drivers

[Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>]

Add support for triggering INTx IRQs by using outbound iATU.
Outbound iATU is utilized to send assert and de-assert INTx TLPs.
The message is generated based on the payloadless Msg TLP with type
0x14, where 0x4 is the routing code implying the Terminate at
Receiver message. The message code is specified as b1000xx for
the INTx assertion and b1001xx for the INTx de-assertion.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
---
 .../pci/controller/dwc/pcie-designware-ep.c   | 71 +++++++++++++++++--
 drivers/pci/controller/dwc/pcie-designware.h  |  2 +
 2 files changed, 69 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
index 96375b0aba82..b35ed2b06193 100644
--- a/drivers/pci/controller/dwc/pcie-designware-ep.c
+++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
@@ -6,6 +6,7 @@
  * Author: Kishon Vijay Abraham I <kishon@xxxxxx>
  */
 
+#include <linux/delay.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
 
@@ -485,14 +486,63 @@ static const struct pci_epc_ops epc_ops = {
 	.get_features		= dw_pcie_ep_get_features,
 };
 
+static int dw_pcie_ep_send_msg(struct dw_pcie_ep *ep, u8 func_no, u8 code,
+			       u8 routing)
+{
+	struct dw_pcie_outbound_atu atu = { 0 };
+	struct pci_epc *epc = ep->epc;
+	int ret;
+
+	atu.func_no = func_no;
+	atu.code = code;
+	atu.routing = routing;
+	atu.type = PCIE_ATU_TYPE_MSG;
+	atu.cpu_addr = ep->intx_mem_phys;
+	atu.size = epc->mem->window.page_size;
+
+	ret = dw_pcie_ep_outbound_atu(ep, &atu);
+	if (ret)
+		return ret;
+
+	writel(0, ep->intx_mem);
+
+	dw_pcie_ep_unmap_addr(epc, func_no, 0, ep->intx_mem_phys);
+
+	return 0;
+}
+
+static int __dw_pcie_ep_raise_intx_irq(struct dw_pcie_ep *ep, u8 func_no,
+					 int intx)
+{
+	int ret;
+
+	ret = dw_pcie_ep_send_msg(ep, func_no, PCI_CODE_ASSERT_INTA + intx,
+				  PCI_MSG_ROUTING_LOCAL);
+	if (ret)
+		return ret;
+
+	/*
+	 * The documents of PCIe and the controller don't mention how long
+	 * the INTx should be asserted. If 10 usec, sometimes it failed.
+	 * So, asserted for 50 usec.
+	 */
+	usleep_range(50, 100);
+
+	return dw_pcie_ep_send_msg(ep, func_no, PCI_CODE_DEASSERT_INTA + intx,
+				   PCI_MSG_ROUTING_LOCAL);
+}
+
 int dw_pcie_ep_raise_intx_irq(struct dw_pcie_ep *ep, u8 func_no)
 {
 	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
 	struct device *dev = pci->dev;
 
-	dev_err(dev, "EP cannot trigger INTx IRQs\n");
+	if (!ep->intx_mem) {
+		dev_err(dev, "INTx not supported\n");
+		return -EOPNOTSUPP;
+	}
 
-	return -EINVAL;
+	return __dw_pcie_ep_raise_intx_irq(ep, func_no, 0);
 }
 EXPORT_SYMBOL_GPL(dw_pcie_ep_raise_intx_irq);
 
@@ -623,6 +673,10 @@ void dw_pcie_ep_exit(struct dw_pcie_ep *ep)
 
 	dw_pcie_edma_remove(pci);
 
+	if (ep->intx_mem)
+		pci_epc_mem_free_addr(epc, ep->intx_mem_phys, ep->intx_mem,
+				      epc->mem->window.page_size);
+
 	pci_epc_mem_free_addr(epc, ep->msi_mem_phys, ep->msi_mem,
 			      epc->mem->window.page_size);
 
@@ -794,9 +848,14 @@ int dw_pcie_ep_init(struct dw_pcie_ep *ep)
 		goto err_exit_epc_mem;
 	}
 
+	ep->intx_mem = pci_epc_mem_alloc_addr(epc, &ep->intx_mem_phys,
+					      epc->mem->window.page_size);
+	if (!ep->intx_mem)
+		dev_warn(dev, "Failed to reserve memory for INTx\n");
+
 	ret = dw_pcie_edma_detect(pci);
 	if (ret)
-		goto err_free_epc_mem;
+		goto err_free_epc_mem_intx;
 
 	if (ep->ops->get_features) {
 		epc_features = ep->ops->get_features(ep);
@@ -813,7 +872,11 @@ int dw_pcie_ep_init(struct dw_pcie_ep *ep)
 err_remove_edma:
 	dw_pcie_edma_remove(pci);
 
-err_free_epc_mem:
+err_free_epc_mem_intx:
+	if (ep->intx_mem)
+		pci_epc_mem_free_addr(epc, ep->intx_mem_phys, ep->intx_mem,
+				      epc->mem->window.page_size);
+
 	pci_epc_mem_free_addr(epc, ep->msi_mem_phys, ep->msi_mem,
 			      epc->mem->window.page_size);
 
diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
index 954d504890a1..8c08159ea08e 100644
--- a/drivers/pci/controller/dwc/pcie-designware.h
+++ b/drivers/pci/controller/dwc/pcie-designware.h
@@ -369,6 +369,8 @@ struct dw_pcie_ep {
 	unsigned long		*ob_window_map;
 	void __iomem		*msi_mem;
 	phys_addr_t		msi_mem_phys;
+	void __iomem		*intx_mem;
+	phys_addr_t		intx_mem_phys;
 	struct pci_epf_bar	*epf_bar[PCI_STD_NUM_BARS];
 };
 
-- 
2.25.1