PCI: aardvark: Add support for PME interrupts

Currently enabling PCI_EXP_RTSTA_PME bit in PCI_EXP_RTCTL register does
nothing. This is because PCIe PME driver expects to receive PCIe interrupt
defined in PCI_EXP_FLAGS_IRQ register, but aardvark hardware does not
trigger PCIe INTx/MSI interrupt for PME event, rather it triggers custom
aardvark interrupt which this driver is not processing yet.

Fix this issue by handling PME interrupt in advk_pcie_handle_int() and
chaining it to PCIe interrupt 0 with generic_handle_domain_irq() (since
aardvark sets PCI_EXP_FLAGS_IRQ to zero). With this change PCIe PME driver
finally starts receiving PME interrupt.

Link: https://lore.kernel.org/r/20220110015018.26359-17-kabel@kernel.org
Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Marek Behún <kabel@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>

Author: pali

drivers/pci/controller/pci-aardvark.c

@@ -1478,6 +1478,18 @@ static void advk_pcie_handle_int(struct advk_pcie *pcie)
 	isr1_mask = advk_readl(pcie, PCIE_ISR1_MASK_REG);
 	isr1_status = isr1_val & ((~isr1_mask) & PCIE_ISR1_ALL_MASK);
 
+	/* Process PME interrupt */
+	if (isr0_status & PCIE_MSG_PM_PME_MASK) {
+		/*
+		 * Do not clear PME interrupt bit in ISR0, it is cleared by IRQ
+		 * receiver by writing to the PCI_EXP_RTSTA register of emulated
+		 * root bridge. Aardvark HW returns zero for PCI_EXP_FLAGS_IRQ,
+		 * so use PCIe interrupt 0.
+		 */
+		if (generic_handle_domain_irq(pcie->irq_domain, 0) == -EINVAL)
+			dev_err_ratelimited(&pcie->pdev->dev, "unhandled PME IRQ\n");
+	}
+
 	/* Process ERR interrupt */
 	if (isr0_status & PCIE_ISR0_ERR_MASK) {
 		advk_writel(pcie, PCIE_ISR0_ERR_MASK, PCIE_ISR0_REG);