irqchip/renesas-rzg2l: Implement restriction when writing ISCR register

[ Upstream commit ef88eef ]

The RZ/G2L manual (chapter "IRQ Status Control Register (ISCR)") describes
the operation to clear interrupts through the ISCR register as follows:

[Write operation]

  When "Falling-edge detection", "Rising-edge detection" or
  "Falling/Rising-edge detection" is set in IITSR:

    - In case ISTAT is 1
	0: IRQn interrupt detection status is cleared.
	1: Invalid to write.
    - In case ISTAT is 0
	Invalid to write.

  When "Low-level detection" is set in IITSR.:
        Invalid to write.

Take the interrupt type into account when clearing interrupts through the
ISCR register to avoid writing the ISCR when the interrupt type is level.

Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20231120111820.87398-6-claudiu.beznea.uj@bp.renesas.com
Stable-dep-of: 9eec61d ("irqchip/renesas-rzg2l: Flush posted write in irq_eoi()")
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/irqchip/irq-renesas-rzg2l.c

@@ -72,11 +72,17 @@ static void rzg2l_irq_eoi(struct irq_data *d)
 	unsigned int hw_irq = irqd_to_hwirq(d) - IRQC_IRQ_START;
 	struct rzg2l_irqc_priv *priv = irq_data_to_priv(d);
 	u32 bit = BIT(hw_irq);
-	u32 reg;
+	u32 iitsr, iscr;
 
-	reg = readl_relaxed(priv->base + ISCR);
-	if (reg & bit)
-		writel_relaxed(reg & ~bit, priv->base + ISCR);
+	iscr = readl_relaxed(priv->base + ISCR);
+	iitsr = readl_relaxed(priv->base + IITSR);
+
+	/*
+	 * ISCR can only be cleared if the type is falling-edge, rising-edge or
+	 * falling/rising-edge.
+	 */
+	if ((iscr & bit) && (iitsr & IITSR_IITSEL_MASK(hw_irq)))
+		writel_relaxed(iscr & ~bit, priv->base + ISCR);
 }
 
 static void rzg2l_tint_eoi(struct irq_data *d)