i2c: exynos5: Add bus clock support

In new Exynos SoCs (like Exynos850) where HSI2C is implemented as a
part of USIv2 block, there are two clocks provided to HSI2C controller:
  - PCLK: bus clock (APB), provides access to register interface
  - IPCLK: operating IP-core clock; SCL is derived from this one

Both clocks have to be asserted for HSI2C to be functional in that case.

Add code to obtain and enable/disable PCLK in addition to already
handled operating clock. Make it optional though, as older Exynos SoC
variants only have one HSI2C clock.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Chanho Park <chanho61.park@samsung.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

Author: Sam Protsenko

drivers/i2c/busses/i2c-exynos5.c

@@ -182,7 +182,8 @@ struct exynos5_i2c {
 	unsigned int		irq;
 
 	void __iomem		*regs;
-	struct clk		*clk;
+	struct clk		*clk;		/* operating clock */
+	struct clk		*pclk;		/* bus clock */
 	struct device		*dev;
 	int			state;
 
@@ -757,17 +758,23 @@ static int exynos5_i2c_xfer(struct i2c_adapter *adap,
 	struct exynos5_i2c *i2c = adap->algo_data;
 	int i, ret;
 
-	ret = clk_enable(i2c->clk);
+	ret = clk_enable(i2c->pclk);
 	if (ret)
 		return ret;
 
+	ret = clk_enable(i2c->clk);
+	if (ret)
+		goto err_pclk;
+
 	for (i = 0; i < num; ++i) {
 		ret = exynos5_i2c_xfer_msg(i2c, msgs + i, i + 1 == num);
 		if (ret)
 			break;
 	}
 
 	clk_disable(i2c->clk);
+err_pclk:
+	clk_disable(i2c->pclk);
 
 	return ret ?: num;
 }
@@ -807,10 +814,18 @@ static int exynos5_i2c_probe(struct platform_device *pdev)
 		return -ENOENT;
 	}
 
-	ret = clk_prepare_enable(i2c->clk);
+	i2c->pclk = devm_clk_get(&pdev->dev, "hsi2c_pclk");
+	if (IS_ERR(i2c->pclk))
+		i2c->pclk = NULL; /* pclk is optional */
+
+	ret = clk_prepare_enable(i2c->pclk);
 	if (ret)
 		return ret;
 
+	ret = clk_prepare_enable(i2c->clk);
+	if (ret)
+		goto err_pclk;
+
 	i2c->regs = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(i2c->regs)) {
 		ret = PTR_ERR(i2c->regs);
@@ -853,11 +868,15 @@ static int exynos5_i2c_probe(struct platform_device *pdev)
 	platform_set_drvdata(pdev, i2c);
 
 	clk_disable(i2c->clk);
+	clk_disable(i2c->pclk);
 
 	return 0;
 
  err_clk:
 	clk_disable_unprepare(i2c->clk);
+
+ err_pclk:
+	clk_disable_unprepare(i2c->pclk);
 	return ret;
 }
 
@@ -868,6 +887,7 @@ static int exynos5_i2c_remove(struct platform_device *pdev)
 	i2c_del_adapter(&i2c->adap);
 
 	clk_unprepare(i2c->clk);
+	clk_unprepare(i2c->pclk);
 
 	return 0;
 }
@@ -879,6 +899,7 @@ static int exynos5_i2c_suspend_noirq(struct device *dev)
 
 	i2c_mark_adapter_suspended(&i2c->adap);
 	clk_unprepare(i2c->clk);
+	clk_unprepare(i2c->pclk);
 
 	return 0;
 }
@@ -888,21 +909,30 @@ static int exynos5_i2c_resume_noirq(struct device *dev)
 	struct exynos5_i2c *i2c = dev_get_drvdata(dev);
 	int ret = 0;
 
-	ret = clk_prepare_enable(i2c->clk);
+	ret = clk_prepare_enable(i2c->pclk);
 	if (ret)
 		return ret;
 
+	ret = clk_prepare_enable(i2c->clk);
+	if (ret)
+		goto err_pclk;
+
 	ret = exynos5_hsi2c_clock_setup(i2c);
-	if (ret) {
-		clk_disable_unprepare(i2c->clk);
-		return ret;
-	}
+	if (ret)
+		goto err_clk;
 
 	exynos5_i2c_init(i2c);
 	clk_disable(i2c->clk);
+	clk_disable(i2c->pclk);
 	i2c_mark_adapter_resumed(&i2c->adap);
 
 	return 0;
+
+err_clk:
+	clk_disable_unprepare(i2c->clk);
+err_pclk:
+	clk_disable_unprepare(i2c->pclk);
+	return ret;
 }
 #endif