irqchip/renesas-rzg2l: Prevent spurious interrupts when setting trigger type

RZ/G2L interrupt chips require that the interrupt is masked before changing
the NMI, IRQ, TINT interrupt settings. Aside of that, after setting an edge
trigger type it is required to clear the interrupt status register in order
to avoid spurious interrupts.

The current implementation fails to do either of that and therefore is
prone to generate spurious interrupts when setting the trigger type.

Address this by:

  - Ensuring that the interrupt is masked at the chip level across the
    update for the TINT chip

  - Clearing the interrupt status register after updating the trigger mode
    for edge type interrupts

[ tglx: Massaged changelog and reverted the spin_lock_irqsave() change as
  	the set_type() callback is always called with interrupts disabled. ]

Fixes: 3fed095 ("irqchip: Add RZ/G2L IA55 Interrupt Controller driver")
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Author: bijudas

drivers/irqchip/irq-renesas-rzg2l.c

@@ -181,8 +181,10 @@ static void rzg2l_irqc_irq_enable(struct irq_data *d)
 
 static int rzg2l_irq_set_type(struct irq_data *d, unsigned int type)
 {
-	unsigned int hw_irq = irqd_to_hwirq(d) - IRQC_IRQ_START;
 	struct rzg2l_irqc_priv *priv = irq_data_to_priv(d);
+	unsigned int hwirq = irqd_to_hwirq(d);
+	u32 iitseln = hwirq - IRQC_IRQ_START;
+	bool clear_irq_int = false;
 	u16 sense, tmp;
 
 	switch (type & IRQ_TYPE_SENSE_MASK) {
@@ -192,14 +194,17 @@ static int rzg2l_irq_set_type(struct irq_data *d, unsigned int type)
 
 	case IRQ_TYPE_EDGE_FALLING:
 		sense = IITSR_IITSEL_EDGE_FALLING;
+		clear_irq_int = true;
 		break;
 
 	case IRQ_TYPE_EDGE_RISING:
 		sense = IITSR_IITSEL_EDGE_RISING;
+		clear_irq_int = true;
 		break;
 
 	case IRQ_TYPE_EDGE_BOTH:
 		sense = IITSR_IITSEL_EDGE_BOTH;
+		clear_irq_int = true;
 		break;
 
 	default:
@@ -208,21 +213,40 @@ static int rzg2l_irq_set_type(struct irq_data *d, unsigned int type)
 
 	raw_spin_lock(&priv->lock);
 	tmp = readl_relaxed(priv->base + IITSR);
-	tmp &= ~IITSR_IITSEL_MASK(hw_irq);
-	tmp |= IITSR_IITSEL(hw_irq, sense);
+	tmp &= ~IITSR_IITSEL_MASK(iitseln);
+	tmp |= IITSR_IITSEL(iitseln, sense);
+	if (clear_irq_int)
+		rzg2l_clear_irq_int(priv, hwirq);
 	writel_relaxed(tmp, priv->base + IITSR);
 	raw_spin_unlock(&priv->lock);
 
 	return 0;
 }
 
+static u32 rzg2l_disable_tint_and_set_tint_source(struct irq_data *d, struct rzg2l_irqc_priv *priv,
+						  u32 reg, u32 tssr_offset, u8 tssr_index)
+{
+	u32 tint = (u32)(uintptr_t)irq_data_get_irq_chip_data(d);
+	u32 tien = reg & (TIEN << TSSEL_SHIFT(tssr_offset));
+
+	/* Clear the relevant byte in reg */
+	reg &= ~(TSSEL_MASK << TSSEL_SHIFT(tssr_offset));
+	/* Set TINT and leave TIEN clear */
+	reg |= tint << TSSEL_SHIFT(tssr_offset);
+	writel_relaxed(reg, priv->base + TSSR(tssr_index));
+
+	return reg | tien;
+}
+
 static int rzg2l_tint_set_edge(struct irq_data *d, unsigned int type)
 {
 	struct rzg2l_irqc_priv *priv = irq_data_to_priv(d);
 	unsigned int hwirq = irqd_to_hwirq(d);
 	u32 titseln = hwirq - IRQC_TINT_START;
+	u32 tssr_offset = TSSR_OFFSET(titseln);
+	u8 tssr_index = TSSR_INDEX(titseln);
 	u8 index, sense;
-	u32 reg;
+	u32 reg, tssr;
 
 	switch (type & IRQ_TYPE_SENSE_MASK) {
 	case IRQ_TYPE_EDGE_RISING:
@@ -244,10 +268,14 @@ static int rzg2l_tint_set_edge(struct irq_data *d, unsigned int type)
 	}
 
 	raw_spin_lock(&priv->lock);
+	tssr = readl_relaxed(priv->base + TSSR(tssr_index));
+	tssr = rzg2l_disable_tint_and_set_tint_source(d, priv, tssr, tssr_offset, tssr_index);
 	reg = readl_relaxed(priv->base + TITSR(index));
 	reg &= ~(IRQ_MASK << (titseln * TITSEL_WIDTH));
 	reg |= sense << (titseln * TITSEL_WIDTH);
 	writel_relaxed(reg, priv->base + TITSR(index));
+	rzg2l_clear_tint_int(priv, hwirq);
+	writel_relaxed(tssr, priv->base + TSSR(tssr_index));
 	raw_spin_unlock(&priv->lock);
 
 	return 0;