linux-kernel - [PATCH AUTOSEL 5.4 32/35] i2c: aspeed: Avoid i2c interrupt status clear race condition.

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Date:   Thu,  7 May 2020 10:28:26 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     ryan_chen <ryan_chen@...eedtech.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Wolfram Sang <wsa@...-dreams.de>,
        Sasha Levin <sashal@...nel.org>, linux-i2c@...r.kernel.org,
        openbmc@...ts.ozlabs.org, linux-arm-kernel@...ts.infradead.org,
        linux-aspeed@...ts.ozlabs.org
Subject: [PATCH AUTOSEL 5.4 32/35] i2c: aspeed: Avoid i2c interrupt status clear race condition.

From: ryan_chen <ryan_chen@...eedtech.com>

[ Upstream commit c926c87b8e36dcc0ea5c2a0a0227ed4f32d0516a ]

In AST2600 there have a slow peripheral bus between CPU and i2c
controller. Therefore GIC i2c interrupt status clear have delay timing,
when CPU issue write clear i2c controller interrupt status. To avoid
this issue, the driver need have read after write clear at i2c ISR.

Fixes: f327c686d3ba ("i2c: aspeed: added driver for Aspeed I2C")
Signed-off-by: ryan_chen <ryan_chen@...eedtech.com>
Acked-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>
[wsa: added Fixes tag]
Signed-off-by: Wolfram Sang <wsa@...-dreams.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/i2c/busses/i2c-aspeed.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
index 7b098ff5f5dd3..dad6e432de89f 100644
--- a/drivers/i2c/busses/i2c-aspeed.c
+++ b/drivers/i2c/busses/i2c-aspeed.c
@@ -603,6 +603,7 @@ static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id)
 	/* Ack all interrupts except for Rx done */
 	writel(irq_received & ~ASPEED_I2CD_INTR_RX_DONE,
 	       bus->base + ASPEED_I2C_INTR_STS_REG);
+	readl(bus->base + ASPEED_I2C_INTR_STS_REG);
 	irq_remaining = irq_received;
 
 #if IS_ENABLED(CONFIG_I2C_SLAVE)
@@ -645,9 +646,11 @@ static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id)
 			irq_received, irq_handled);
 
 	/* Ack Rx done */
-	if (irq_received & ASPEED_I2CD_INTR_RX_DONE)
+	if (irq_received & ASPEED_I2CD_INTR_RX_DONE) {
 		writel(ASPEED_I2CD_INTR_RX_DONE,
 		       bus->base + ASPEED_I2C_INTR_STS_REG);
+		readl(bus->base + ASPEED_I2C_INTR_STS_REG);
+	}
 	spin_unlock(&bus->lock);
 	return irq_remaining ? IRQ_NONE : IRQ_HANDLED;
 }
-- 
2.20.1