mfd: qcom-pm8xxx: Fix potential deadlock on &chip->pm_irq_lock

As &chip->pm_irq_lock is acquired by pm8xxx_irq_handler() under irq
context, other process context code should disable irq before acquiring
the lock.

Since .irq_set_type and .irq_get_irqchip_state callbacks are generally
executed from process context without irq disabled by default, the same
lock acquision should disable irq.

Possible deadlock scenario
pm8xxx_irq_set_type()
-> pm8xxx_config_irq()
-> spin_lock(&chip->pm_irq_lock)
<irq interrupt>
-> pm8xxx_irq_handler()
-> pm8xxx_irq_master_handler()
-> pm8xxx_irq_block_handler()
-> pm8xxx_read_block_irq()
-> spin_lock(&chip->pm_irq_lock) (deadlock here)

This flaw was found using an experimental static analysis tool we are
developing for irq-related deadlock.

Fix the potential deadlock by spin_lock_irqsave().

Signed-off-by: Chengfeng Ye <[e-mail]>
Reviewed-by: Bjorn Andersson <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Lee Jones <[e-mail]>

drivers/mfd/qcom-pm8xxx.c

···
 pm8xxx_config_irq(struct pm_irq_chip *chip, unsigned int bp, unsigned int cp)
 {
 	int	rc;
+	unsigned long flags;
 
-	spin_lock(&chip->pm_irq_lock);
+	spin_lock_irqsave(&chip->pm_irq_lock, flags);
 	rc = regmap_write(chip->regmap, SSBI_REG_ADDR_IRQ_BLK_SEL, bp);
 	if (rc) {
 		pr_err("Failed Selecting Block %d rc=%d\n", bp, rc);
···
 	if (rc)
 		pr_err("Failed Configuring IRQ rc=%d\n", rc);
 bail:
-	spin_unlock(&chip->pm_irq_lock);
+	spin_unlock_irqrestore(&chip->pm_irq_lock, flags);
 	return rc;
 }
 
···
 	struct pm_irq_chip *chip = irq_data_get_irq_chip_data(d);
 	unsigned int pmirq = irqd_to_hwirq(d);
 	unsigned int bits;
+	unsigned long flags;
 	int irq_bit;
 	u8 block;
 	int rc;
···
 	block = pmirq / 8;
 	irq_bit = pmirq % 8;
 
-	spin_lock(&chip->pm_irq_lock);
+	spin_lock_irqsave(&chip->pm_irq_lock, flags);
 	rc = regmap_write(chip->regmap, SSBI_REG_ADDR_IRQ_BLK_SEL, block);
 	if (rc) {
 		pr_err("Failed Selecting Block %d rc=%d\n", block, rc);
···
 
 	*state = !!(bits & BIT(irq_bit));
 bail:
-	spin_unlock(&chip->pm_irq_lock);
+	spin_unlock_irqrestore(&chip->pm_irq_lock, flags);
 
 	return rc;
 }