[PATCH v5 2/2] i2c: imx-lpi2c: reset controller in probe stage

[carlos.song at oss.nxp.com]

From: Carlos Song <carlos.song at nxp.com>

Reset I2C controller in probe stage to avoid unexpected LPI2C controller
state left from previous stages and hang system boot.

Per the LPI2C reference manual, section 7.1.4 "Controller Control (MCR)"
and 7.1.20 Target Control (SCR), the RST bit (bit 1) description states:

  "The reset takes effect immediately and remains asserted until negated
  by software. There is no minimum delay required before clearing the
  software reset."

Therefore, it is safe to write 0 to MCR and SCR immediately after
asserting the RST bit without any additional delay.

Signed-off-by: Carlos Song <carlos.song at nxp.com>
---
 drivers/i2c/busses/i2c-imx-lpi2c.c | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c
index 2dc4331ed796..9fbdce85d7ca 100644
--- a/drivers/i2c/busses/i2c-imx-lpi2c.c
+++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
@@ -1510,11 +1510,6 @@ static int lpi2c_imx_probe(struct platform_device *pdev)
 	if (ret)
 		lpi2c_imx->bitrate = I2C_MAX_STANDARD_MODE_FREQ;
 
-	ret = devm_request_irq(&pdev->dev, lpi2c_imx->irq, lpi2c_imx_isr, IRQF_NO_SUSPEND,
-			       pdev->name, lpi2c_imx);
-	if (ret)
-		return dev_err_probe(&pdev->dev, ret, "can't claim irq %d\n", lpi2c_imx->irq);
-
 	i2c_set_adapdata(&lpi2c_imx->adapter, lpi2c_imx);
 	platform_set_drvdata(pdev, lpi2c_imx);
 
@@ -1551,6 +1546,22 @@ static int lpi2c_imx_probe(struct platform_device *pdev)
 	pm_runtime_set_active(&pdev->dev);
 	pm_runtime_enable(&pdev->dev);
 
+	/*
+	 * Reset all internal controller registers of both Master and Target
+	 * to avoid effects of previous status.
+	 */
+	writel(MCR_RST, lpi2c_imx->base + LPI2C_MCR);
+	writel(SCR_RST, lpi2c_imx->base + LPI2C_SCR);
+	writel(0, lpi2c_imx->base + LPI2C_MCR);
+	writel(0, lpi2c_imx->base + LPI2C_SCR);
+
+	ret = devm_request_irq(&pdev->dev, lpi2c_imx->irq, lpi2c_imx_isr, IRQF_NO_SUSPEND,
+			       pdev->name, lpi2c_imx);
+	if (ret) {
+		dev_err_probe(&pdev->dev, ret, "can't claim irq %d\n", lpi2c_imx->irq);
+		goto rpm_disable;
+	}
+
 	temp = readl(lpi2c_imx->base + LPI2C_PARAM);
 	lpi2c_imx->txfifosize = 1 << (temp & 0x0f);
 	lpi2c_imx->rxfifosize = 1 << ((temp >> 8) & 0x0f);
-- 
2.43.0