linux-kernel - [PATCH 2/2] i2c designware add support of I2C standard mode

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Message-Id: <1381244455-3836-2-git-send-email-romainba@abilis.com>
Date:	Tue,  8 Oct 2013 17:00:55 +0200
From:	Romain Baeriswyl <Romain.Baeriswyl@...lis.com>
To:	Wolfram Sang <wsa@...-dreams.de>
Cc:	Rob Herring <rob.herring@...xeda.com>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Stephen Warren <swarren@...dotorg.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Rob Landley <rob@...dley.net>,
	Pierrick Hascoet <pierrick.hascoet@...lis.com>,
	Vineet Gupta <vgupta@...opsys.com>,
	Christian Ruppert <christian.ruppert@...lis.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Chiau Ee Chew <chiau.ee.chew@...el.com>,
	Shinya Kuribayashi <skuribay@...ox.com>,
	Jean Delvare <khali@...ux-fr.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	devicetree@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
	Romain Baeriswyl <romainba@...lis.com>
Subject: [PATCH 2/2] i2c designware add support of I2C standard mode

Some legacy devices support ony I2C standard mode at 100kHz. 
This patch allows to select the standard mode through the DTS 
with the use of the existing clock-frequency parameter.

When clock-frequency parameter is not set, the fast mode is selected.
Only when the parameter is set at 100000, the standard mode is selected.

Signed-off-by: Romain Baeriswyl <romainba@...lis.com>
Reviewed-by: Christian Ruppert <christian.ruppert@...lis.com>
---
 .../devicetree/bindings/i2c/i2c-designware.txt     |    1 +
 drivers/i2c/busses/i2c-designware-platdrv.c        |   17 +++++++++++++++--
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/i2c/i2c-designware.txt b/Documentation/devicetree/bindings/i2c/i2c-designware.txt
index 5199b0c..16d0bef 100644
--- a/Documentation/devicetree/bindings/i2c/i2c-designware.txt
+++ b/Documentation/devicetree/bindings/i2c/i2c-designware.txt
@@ -9,6 +9,7 @@ Required properties :
 Recommended properties :
 
  - clock-frequency : desired I2C bus clock frequency in Hz.
+   Only standard mode at 100kHz and fast mode at 400kHz are supported.
 
 Optional properties :
  - i2c-sda-hold-time-ns : should contain the SDA hold time in nanoseconds.
diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index 0d6fe47..5f06848 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -87,6 +87,7 @@ static int dw_i2c_probe(struct platform_device *pdev)
 	struct i2c_adapter *adap;
 	struct resource *mem;
 	int irq, r;
+	u32 clk_freq;
 
 	irq = platform_get_irq(pdev, 0);
 	if (irq < 0) {
@@ -122,6 +123,9 @@ static int dw_i2c_probe(struct platform_device *pdev)
 		return PTR_ERR(dev->clk);
 	clk_prepare_enable(dev->clk);
 
+	/* fast mode by default */
+	clk_freq = 400000;
+
 	if (pdev->dev.of_node) {
 		u32 ht = 0;
 		u32 ic_clk = dev->get_clk_rate_khz(dev);
@@ -136,6 +140,11 @@ static int dw_i2c_probe(struct platform_device *pdev)
 		of_property_read_u32(pdev->dev.of_node,
 				     "i2c-scl-falling-time-ns",
 				     &dev->scl_falling_time);
+
+		of_property_read_u32(pdev->dev.of_node, "clock-frequency",
+				     &clk_freq);
+		if (clk_freq != 100000 && clk_freq != 400000)
+			return -EINVAL;
 	}
 
 	dev->functionality =
@@ -145,8 +154,12 @@ static int dw_i2c_probe(struct platform_device *pdev)
 		I2C_FUNC_SMBUS_BYTE_DATA |
 		I2C_FUNC_SMBUS_WORD_DATA |
 		I2C_FUNC_SMBUS_I2C_BLOCK;
-	dev->master_cfg =  DW_IC_CON_MASTER | DW_IC_CON_SLAVE_DISABLE |
-		DW_IC_CON_RESTART_EN | DW_IC_CON_SPEED_FAST;
+	if (clk_freq == 100000)
+		dev->master_cfg =  DW_IC_CON_MASTER | DW_IC_CON_SLAVE_DISABLE |
+			DW_IC_CON_RESTART_EN | DW_IC_CON_SPEED_STD;
+	else
+		dev->master_cfg =  DW_IC_CON_MASTER | DW_IC_CON_SLAVE_DISABLE |
+			DW_IC_CON_RESTART_EN | DW_IC_CON_SPEED_FAST;
 
 	/* Try first if we can configure the device from ACPI */
 	r = dw_i2c_acpi_configure(pdev);
-- 
1.7.1

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