misc: microchip: pci1xxxx: Add GPIO Wakeup Support

The patch adds PIO asynchronous wakeup support while PIO PCIe Endpoint
function is in D3 state. When such a wakeup event occurs, the PIO
asserts a PIO_WAKE signal, which in turn triggers PCIe Wake signaling.
This wake request should trigger the PCIe Host to take the PIO PCIe
Endpoint function into the D0 device state.

The device supports up to 96 PIOs distributed across three GPIO banks.
During suspend and resume, the driver checks the status of each GPIO bank
to determine if any GPIOs with wake masking enabled have triggered an
event. Upon resume, PIOxx_STATUS register must be cleared by software
explicitly to enable the detection of the next transition.

Signed-off-by: Rengarajan S <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/misc/mchp_pci1xxxx/mchp_pci1xxxx_gpio.c

···
 	raw_spinlock_t wa_lock;
 	struct gpio_chip gpio;
 	spinlock_t lock;
+	u32 gpio_wake_mask[3];
 	int irq_base;
 	u8 dev_rev;
 };
···
 	return true;
 }
 
+static int pci1xxxx_gpio_set_wake(struct irq_data *data, unsigned int enable)
+{
+	struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
+	struct pci1xxxx_gpio *priv = gpiochip_get_data(chip);
+	unsigned int gpio = irqd_to_hwirq(data);
+	unsigned int bitpos = gpio % 32;
+	unsigned int bank = gpio / 32;
+
+	if (enable)
+		priv->gpio_wake_mask[bank] |= (1 << bitpos);
+	else
+		priv->gpio_wake_mask[bank] &= ~(1 << bitpos);
+
+	return 0;
+}
+
 static irqreturn_t pci1xxxx_gpio_irq_handler(int irq, void *dev_id)
 {
 	struct pci1xxxx_gpio *priv = dev_id;
···
 	.irq_mask = pci1xxxx_gpio_irq_mask,
 	.irq_unmask = pci1xxxx_gpio_irq_unmask,
 	.irq_set_type = pci1xxxx_gpio_set_type,
+	.irq_set_wake = pci1xxxx_gpio_set_wake,
 	.flags = IRQCHIP_IMMUTABLE,
 	GPIOCHIP_IRQ_RESOURCE_HELPERS,
 };
···
 static int pci1xxxx_gpio_suspend(struct device *dev)
 {
 	struct pci1xxxx_gpio *priv = dev_get_drvdata(dev);
+	struct device *parent = priv->aux_dev->dev.parent;
+	struct pci_dev *pcidev = to_pci_dev(parent);
+	unsigned int gpio_bank_base;
+	unsigned int wake_mask;
+	unsigned int gpiobank;
 	unsigned long flags;
+
+	for (gpiobank = 0; gpiobank < 3; gpiobank++) {
+		wake_mask = priv->gpio_wake_mask[gpiobank];
+
+		if (wake_mask) {
+			gpio_bank_base = gpiobank * 32;
+
+			pci1xxx_assign_bit(priv->reg_base,
+					   PIO_PCI_CTRL_REG_OFFSET, 0, true);
+			writel(~wake_mask, priv->reg_base +
+			       WAKEMASK_OFFSET(gpio_bank_base));
+		}
+	}
 
 	spin_lock_irqsave(&priv->lock, flags);
 	pci1xxx_assign_bit(priv->reg_base, PIO_GLOBAL_CONFIG_OFFSET,
···
 
 	spin_unlock_irqrestore(&priv->lock, flags);
 
+	device_set_wakeup_enable(&pcidev->dev, true);
+	pci_wake_from_d3(pcidev, true);
+
 	return 0;
 }
 
 static int pci1xxxx_gpio_resume(struct device *dev)
 {
 	struct pci1xxxx_gpio *priv = dev_get_drvdata(dev);
+	struct device *parent = priv->aux_dev->dev.parent;
+	struct pci_dev *pcidev = to_pci_dev(parent);
+	unsigned int gpio_bank_base;
+	unsigned int wake_mask;
+	unsigned int gpiobank;
 	unsigned long flags;
+
+	for (gpiobank = 0; gpiobank < 3; gpiobank++) {
+		wake_mask = priv->gpio_wake_mask[gpiobank];
+
+		if (wake_mask) {
+			gpio_bank_base = gpiobank * 32;
+
+			writel(wake_mask, priv->reg_base +
+			       INTR_STAT_OFFSET(gpio_bank_base));
+			pci1xxx_assign_bit(priv->reg_base,
+					   PIO_PCI_CTRL_REG_OFFSET, 0, false);
+			writel(0xffffffff, priv->reg_base +
+			       WAKEMASK_OFFSET(gpio_bank_base));
+		}
+	}
 
 	spin_lock_irqsave(&priv->lock, flags);
 	pci1xxx_assign_bit(priv->reg_base, PIO_GLOBAL_CONFIG_OFFSET,
···
 		pci1xxx_assign_bit(priv->reg_base, PERI_GEN_RESET, 17, false);
 
 	spin_unlock_irqrestore(&priv->lock, flags);
+
+	pci_wake_from_d3(pcidev, false);
 
 	return 0;
 }