linux-kernel - [PATCH v2 1/3] i2c: imx: Fix reset of I2SR

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Date:   Fri, 2 Oct 2020 17:23:03 +0200
From:   Christian Eggers <ceggers@...i.de>
To:     Oleksij Rempel <linux@...pel-privat.de>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
CC:     Pengutronix Kernel Team <kernel@...gutronix.de>,
        NXP Linux Team <linux-imx@....com>,
        <linux-i2c@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, Christian Eggers <ceggers@...i.de>,
        <stable@...r.kernel.org>
Subject: [PATCH v2 1/3] i2c: imx: Fix reset of I2SR_IAL flag

According to the "VFxxx Controller Reference Manual" (and the comment
block starting at line 97), Vybrid requires writing a one for clearing
an interrupt flag. Syncing the method for clearing I2SR_IIF in
i2c_imx_isr().

Signed-off-by: Christian Eggers <ceggers@...i.de>
Cc: stable@...r.kernel.org
---
 drivers/i2c/busses/i2c-imx.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
index 0ab5381aa012..34648df7f1a6 100644
--- a/drivers/i2c/busses/i2c-imx.c
+++ b/drivers/i2c/busses/i2c-imx.c
@@ -424,7 +424,12 @@ static int i2c_imx_bus_busy(struct imx_i2c_struct *i2c_imx, int for_busy, bool a
 
 		/* check for arbitration lost */
 		if (temp & I2SR_IAL) {
-			temp &= ~I2SR_IAL;
+			/*
+			 * i2sr_clr_opcode is the value to clear all interrupts.
+			 * Here we want to clear only I2SR_IAL, so we write
+			 * ~i2sr_clr_opcode with just the I2SR_IAL bit toggled.
+			 */
+			temp = ~i2c_imx->hwdata->i2sr_clr_opcode ^ I2SR_IAL;
 			imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2SR);
 			return -EAGAIN;
 		}
@@ -623,8 +628,12 @@ static irqreturn_t i2c_imx_isr(int irq, void *dev_id)
 	if (temp & I2SR_IIF) {
 		/* save status register */
 		i2c_imx->i2csr = temp;
-		temp &= ~I2SR_IIF;
-		temp |= (i2c_imx->hwdata->i2sr_clr_opcode & I2SR_IIF);
+		/*
+		 * i2sr_clr_opcode is the value to clear all interrupts.
+		 * Here we want to clear only I2SR_IIF, so we write
+		 * ~i2sr_clr_opcode with just the I2SR_IIF bit toggled.
+		 */
+		temp = ~i2c_imx->hwdata->i2sr_clr_opcode ^ I2SR_IIF;
 		imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2SR);
 		wake_up(&i2c_imx->queue);
 		return IRQ_HANDLED;
-- 
Christian Eggers
Embedded software developer

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