[PATCH 1/5] i2c: i2c-stm32f7: disable/restore Fast Mode Plus bits in low power modes

[Alain Volmat <alain.volmat@xxxxxx>]

Defer the initial enabling of the Fast Mode Plus bits after the
stm32f7_i2c_setup_timing call in probe function in order to avoid
enabling them if speed is downgraded.
Clear & restore the Fast Mode Plus bits in the suspend/resume
handlers of the driver.

Signed-off-by: Alain Volmat <alain.volmat@xxxxxx>
---
 drivers/i2c/busses/i2c-stm32f7.c | 48 +++++++++++++++++++++++++++++++++-------
 1 file changed, 40 insertions(+), 8 deletions(-)

diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
index 844a22d64aa8..1a3b3fa582ff 100644
--- a/drivers/i2c/busses/i2c-stm32f7.c
+++ b/drivers/i2c/busses/i2c-stm32f7.c
@@ -303,6 +303,8 @@ struct stm32f7_i2c_msg {
  * @dma: dma data
  * @use_dma: boolean to know if dma is used in the current transfer
  * @regmap: holds SYSCFG phandle for Fast Mode Plus bits
+ * @regmap_reg: register address for setting Fast Mode Plus bits
+ * @regmap_mask: mask for Fast Mode Plus bits in set register
  * @wakeup_src: boolean to know if the device is a wakeup source
  */
 struct stm32f7_i2c_dev {
@@ -326,6 +328,8 @@ struct stm32f7_i2c_dev {
 	struct stm32_i2c_dma *dma;
 	bool use_dma;
 	struct regmap *regmap;
+	u32 regmap_reg;
+	u32 regmap_mask;
 	bool wakeup_src;
 };
 
@@ -1815,12 +1819,25 @@ static int stm32f7_i2c_unreg_slave(struct i2c_client *slave)
 	return 0;
 }
 
+static int stm32f7_i2c_write_fm_plus_bits(struct stm32f7_i2c_dev *i2c_dev,
+					  bool enable)
+{
+	if (i2c_dev->speed != STM32_I2C_SPEED_FAST_PLUS ||
+	    IS_ERR_OR_NULL(i2c_dev->regmap)) {
+		/* Optional */
+		return 0;
+	}
+
+	return regmap_update_bits(i2c_dev->regmap, i2c_dev->regmap_reg,
+				  i2c_dev->regmap_mask,
+				  enable ? i2c_dev->regmap_mask : 0);
+}
+
 static int stm32f7_i2c_setup_fm_plus_bits(struct platform_device *pdev,
 					  struct stm32f7_i2c_dev *i2c_dev)
 {
 	struct device_node *np = pdev->dev.of_node;
 	int ret;
-	u32 reg, mask;
 
 	i2c_dev->regmap = syscon_regmap_lookup_by_phandle(np, "st,syscfg-fmp");
 	if (IS_ERR(i2c_dev->regmap)) {
@@ -1828,15 +1845,17 @@ static int stm32f7_i2c_setup_fm_plus_bits(struct platform_device *pdev,
 		return 0;
 	}
 
-	ret = of_property_read_u32_index(np, "st,syscfg-fmp", 1, &reg);
+	ret = of_property_read_u32_index(np, "st,syscfg-fmp", 1,
+					 &i2c_dev->regmap_reg);
 	if (ret)
 		return ret;
 
-	ret = of_property_read_u32_index(np, "st,syscfg-fmp", 2, &mask);
+	ret = of_property_read_u32_index(np, "st,syscfg-fmp", 2,
+					 &i2c_dev->regmap_mask);
 	if (ret)
 		return ret;
 
-	return regmap_update_bits(i2c_dev->regmap, reg, mask, mask);
+	return 0;
 }
 
 static u32 stm32f7_i2c_func(struct i2c_adapter *adap)
@@ -1914,9 +1933,6 @@ static int stm32f7_i2c_probe(struct platform_device *pdev)
 				       &clk_rate);
 	if (!ret && clk_rate >= 1000000) {
 		i2c_dev->speed = STM32_I2C_SPEED_FAST_PLUS;
-		ret = stm32f7_i2c_setup_fm_plus_bits(pdev, i2c_dev);
-		if (ret)
-			goto clk_free;
 	} else if (!ret && clk_rate >= 400000) {
 		i2c_dev->speed = STM32_I2C_SPEED_FAST;
 	} else if (!ret && clk_rate >= 100000) {
@@ -1976,6 +1992,15 @@ static int stm32f7_i2c_probe(struct platform_device *pdev)
 	if (ret)
 		goto clk_free;
 
+	if (i2c_dev->speed == STM32_I2C_SPEED_FAST_PLUS) {
+		ret = stm32f7_i2c_setup_fm_plus_bits(pdev, i2c_dev);
+		if (ret)
+			goto clk_free;
+		ret = stm32f7_i2c_write_fm_plus_bits(i2c_dev, 1);
+		if (ret)
+			goto clk_free;
+	}
+
 	adap = &i2c_dev->adap;
 	i2c_set_adapdata(adap, i2c_dev);
 	snprintf(adap->name, sizeof(adap->name), "STM32F7 I2C(%pa)",
@@ -2000,7 +2025,7 @@ static int stm32f7_i2c_probe(struct platform_device *pdev)
 		if (ret != -EPROBE_DEFER)
 			dev_err(&pdev->dev,
 				"Failed to request dma error %i\n", ret);
-		goto clk_free;
+		goto fmp_clear;
 	}
 
 	if (i2c_dev->wakeup_src) {
@@ -2054,6 +2079,9 @@ static int stm32f7_i2c_probe(struct platform_device *pdev)
 		i2c_dev->dma = NULL;
 	}
 
+fmp_clear:
+	stm32f7_i2c_write_fm_plus_bits(i2c_dev, 0);
+
 clk_free:
 	clk_disable_unprepare(i2c_dev->clk);
 
@@ -2086,6 +2114,8 @@ static int stm32f7_i2c_remove(struct platform_device *pdev)
 		i2c_dev->dma = NULL;
 	}
 
+	stm32f7_i2c_write_fm_plus_bits(i2c_dev, 0);
+
 	clk_disable_unprepare(i2c_dev->clk);
 
 	return 0;
@@ -2133,6 +2163,7 @@ stm32f7_i2c_regs_backup(struct stm32f7_i2c_dev *i2c_dev)
 	backup_regs->oar2 = readl_relaxed(i2c_dev->base + STM32F7_I2C_OAR2);
 	backup_regs->pecr = readl_relaxed(i2c_dev->base + STM32F7_I2C_PECR);
 	backup_regs->tmgr = readl_relaxed(i2c_dev->base + STM32F7_I2C_TIMINGR);
+	stm32f7_i2c_write_fm_plus_bits(i2c_dev, 0);
 
 	pm_runtime_put_sync(i2c_dev->dev);
 
@@ -2165,6 +2196,7 @@ stm32f7_i2c_regs_restore(struct stm32f7_i2c_dev *i2c_dev)
 	writel_relaxed(backup_regs->oar1, i2c_dev->base + STM32F7_I2C_OAR1);
 	writel_relaxed(backup_regs->oar2, i2c_dev->base + STM32F7_I2C_OAR2);
 	writel_relaxed(backup_regs->pecr, i2c_dev->base + STM32F7_I2C_PECR);
+	stm32f7_i2c_write_fm_plus_bits(i2c_dev, 1);
 
 	pm_runtime_put_sync(i2c_dev->dev);
 
-- 
2.7.4