linux-kernel - [PATCH 3/4] i2c: cadence: Implement save restore

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Date:   Mon,  9 Dec 2019 16:10:51 +0530
From:   shubhrajyoti.datta@...il.com
To:     linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org
Cc:     michal.simek@...inx.com,
        Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>,
        Shubhrajyoti Datta <shubhraj@...inx.com>
Subject: [PATCH 3/4] i2c: cadence: Implement save restore

From: Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>

Implement save restore for i2c module.
Since we have only a couple of registers
an unconditional restore is done.

Acked-by: Michal Simek <michal.simek@...inx.com>
Signed-off-by: Shubhrajyoti Datta <shubhraj@...inx.com>
Signed-off-by: Michal Simek <michal.simek@...inx.com>
Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>
---
 drivers/i2c/busses/i2c-cadence.c | 41 ++++++++++++++++++++++++++--------------
 1 file changed, 27 insertions(+), 14 deletions(-)

diff --git a/drivers/i2c/busses/i2c-cadence.c b/drivers/i2c/busses/i2c-cadence.c
index 08427e9..8a2983e 100644
--- a/drivers/i2c/busses/i2c-cadence.c
+++ b/drivers/i2c/busses/i2c-cadence.c
@@ -138,6 +138,7 @@
  * @clk:		Pointer to struct clk
  * @clk_rate_change_nb:	Notifier block for clock rate changes
  * @quirks:		flag for broken hold bit usage in r1p10
+ * @ctrl_reg:		Cached value of the control register.
  */
 struct cdns_i2c {
 	struct device		*dev;
@@ -158,6 +159,7 @@ struct cdns_i2c {
 	struct clk *clk;
 	struct notifier_block clk_rate_change_nb;
 	u32 quirks;
+	u32 ctrl_reg;
 };
 
 struct cdns_platform_data {
@@ -748,12 +750,11 @@ static int cdns_i2c_setclk(unsigned long clk_in, struct cdns_i2c *id)
 	if (ret)
 		return ret;
 
-	ctrl_reg = cdns_i2c_readreg(CDNS_I2C_CR_OFFSET);
+	ctrl_reg = id->ctrl_reg;
 	ctrl_reg &= ~(CDNS_I2C_CR_DIVA_MASK | CDNS_I2C_CR_DIVB_MASK);
 	ctrl_reg |= ((div_a << CDNS_I2C_CR_DIVA_SHIFT) |
 			(div_b << CDNS_I2C_CR_DIVB_SHIFT));
-	cdns_i2c_writereg(ctrl_reg, CDNS_I2C_CR_OFFSET);
-
+	id->ctrl_reg = ctrl_reg;
 	return 0;
 }
 
@@ -837,6 +838,26 @@ static int __maybe_unused cdns_i2c_runtime_suspend(struct device *dev)
 }
 
 /**
+ * cdns_i2c_init -  Controller initialisation
+ * @id:		Device private data structure
+ *
+ * Initialise the i2c controller.
+ *
+ */
+static void cdns_i2c_init(struct cdns_i2c *id)
+{
+	cdns_i2c_writereg(id->ctrl_reg, CDNS_I2C_CR_OFFSET);
+	/*
+	 * Cadence I2C controller has a bug wherein it generates
+	 * invalid read transaction after HW timeout in master receiver mode.
+	 * HW timeout is not used by this driver and the interrupt is disabled.
+	 * But the feature itself cannot be disabled. Hence maximum value
+	 * is written to this register to reduce the chances of error.
+	 */
+	cdns_i2c_writereg(CDNS_I2C_TIMEOUT_MAX, CDNS_I2C_TIME_OUT_OFFSET);
+}
+
+/**
  * cdns_i2c_runtime_resume - Runtime resume
  * @dev:	Address of the platform_device structure
  *
@@ -854,6 +875,7 @@ static int __maybe_unused cdns_i2c_runtime_resume(struct device *dev)
 		dev_err(dev, "Cannot enable clock.\n");
 		return ret;
 	}
+	cdns_i2c_init(xi2c);
 
 	return 0;
 }
@@ -947,8 +969,7 @@ static int cdns_i2c_probe(struct platform_device *pdev)
 	if (ret || (id->i2c_clk > CDNS_I2C_SPEED_MAX))
 		id->i2c_clk = CDNS_I2C_SPEED_DEFAULT;
 
-	cdns_i2c_writereg(CDNS_I2C_CR_ACK_EN | CDNS_I2C_CR_NEA | CDNS_I2C_CR_MS,
-			  CDNS_I2C_CR_OFFSET);
+	id->ctrl_reg = CDNS_I2C_CR_ACK_EN | CDNS_I2C_CR_NEA | CDNS_I2C_CR_MS;
 
 	ret = cdns_i2c_setclk(id->input_clk, id);
 	if (ret) {
@@ -963,15 +984,7 @@ static int cdns_i2c_probe(struct platform_device *pdev)
 		dev_err(&pdev->dev, "cannot get irq %d\n", id->irq);
 		goto err_clk_dis;
 	}
-
-	/*
-	 * Cadence I2C controller has a bug wherein it generates
-	 * invalid read transaction after HW timeout in master receiver mode.
-	 * HW timeout is not used by this driver and the interrupt is disabled.
-	 * But the feature itself cannot be disabled. Hence maximum value
-	 * is written to this register to reduce the chances of error.
-	 */
-	cdns_i2c_writereg(CDNS_I2C_TIMEOUT_MAX, CDNS_I2C_TIME_OUT_OFFSET);
+	cdns_i2c_init(id);
 
 	ret = i2c_add_adapter(&id->adap);
 	if (ret < 0)
-- 
2.1.1