PCI: tegra194: Move dw_pcie_ep_linkup() to threaded IRQ handler

dw_pcie_ep_linkup() may take more time to execute depending on the EPF
driver implementation. Calling this API in the hard IRQ handler is not
encouraged since the hard IRQ handlers are supposed to complete quickly.

So move the dw_pcie_ep_linkup() call to threaded IRQ handler.

Link: https://lore.kernel.org/linux-pci/[e-mail]
Signed-off-by: Manivannan Sadhasivam <[e-mail]>
Signed-off-by: Krzysztof Wilczyński <[e-mail]>
Reviewed-by: Vidya Sagar <[e-mail]>

drivers/pci/controller/dwc/pcie-tegra194.c

···
 	struct gpio_desc *pex_refclk_sel_gpiod;
 	unsigned int pex_rst_irq;
 	int ep_state;
+	long link_status;
 };
 
 static inline struct tegra_pcie_dw *to_tegra_pcie(struct dw_pcie *pci)
···
 static irqreturn_t tegra_pcie_ep_irq_thread(int irq, void *arg)
 {
 	struct tegra_pcie_dw *pcie = arg;
+	struct dw_pcie_ep *ep = &pcie->pci.ep;
 	struct dw_pcie *pci = &pcie->pci;
 	u32 val, speed;
+
+	if (test_and_clear_bit(0, &pcie->link_status))
+		dw_pcie_ep_linkup(ep);
 
 	speed = dw_pcie_readw_dbi(pci, pcie->pcie_cap_base + PCI_EXP_LNKSTA) &
 		PCI_EXP_LNKSTA_CLS;
···
 static irqreturn_t tegra_pcie_ep_hard_irq(int irq, void *arg)
 {
 	struct tegra_pcie_dw *pcie = arg;
-	struct dw_pcie_ep *ep = &pcie->pci.ep;
 	int spurious = 1;
 	u32 status_l0, status_l1, link_status;
 
···
 			link_status = appl_readl(pcie, APPL_LINK_STATUS);
 			if (link_status & APPL_LINK_STATUS_RDLH_LINK_UP) {
 				dev_dbg(pcie->dev, "Link is up with Host\n");
-				dw_pcie_ep_linkup(ep);
+				set_bit(0, &pcie->link_status);
+				return IRQ_WAKE_THREAD;
 			}
 		}