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From:   Claudiu <claudiu.beznea@tuxon.dev>
To:     tglx@linutronix.de, robh+dt@kernel.org,
        krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org,
        geert+renesas@glider.be, magnus.damm@gmail.com,
        mturquette@baylibre.com, sboyd@kernel.org,
        prabhakar.mahadev-lad.rj@bp.renesas.com
Cc:     linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
        linux-renesas-soc@vger.kernel.org, linux-clk@vger.kernel.org,
        Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Subject: [PATCH v2 6/9] irqchip/renesas-rzg2l: Implement restriction when writing ISCR register
Date:   Wed, 15 Nov 2023 16:27:46 +0200
Message-Id: <20231115142749.853106-7-claudiu.beznea.uj@bp.renesas.com>
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From: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>

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 interrupt type is
level.

Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
---

Changes in v2:
- adapted according to review comments
- improved commit description
- used uppercase letter after ":" in patch title

 drivers/irqchip/irq-renesas-rzg2l.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/irqchip/irq-renesas-rzg2l.c b/drivers/irqchip/irq-renesas-rzg2l.c
index d666912adc74..a77ac6e1606f 100644
--- a/drivers/irqchip/irq-renesas-rzg2l.c
+++ b/drivers/irqchip/irq-renesas-rzg2l.c
@@ -78,11 +78,17 @@ 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)
-- 
2.39.2