linux-kernel - [PATCH REBASE] i2c-designware: make SDA hold time configurable

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Date:	Tue, 14 May 2013 15:04:02 +0200
From:	Christian Ruppert <christian.ruppert@...lis.com>
To:	Wolfram Sang <wsa@...-dreams.de>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	linux-i2c@...r.kernel.org
Cc:	"Ben Dooks (embedded platforms)" <ben-linux@...ff.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	Rob Herring <rob.herring@...xeda.com>,
	Rob Landley <rob@...dley.net>,
	devicetree-discuss@...ts.ozlabs.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Vineet Gupta <Vineet.Gupta1@...opsys.com>,
	Pierrick Hascoet <pierrick.hascoet@...lis.com>,
	Christian Ruppert <christian.ruppert@...lis.com>
Subject: [PATCH REBASE] i2c-designware: make SDA hold time configurable

This patch makes the SDA hold time configurable through device tree.

[rebased to i2c-current/i2c-next/mainline-3.10-rc1]

Signed-off-by: Christian Ruppert <christian.ruppert@...lis.com>
Signed-off-by: Pierrick Hascoet <pierrick.hascoet@...lis.com>
---
 .../devicetree/bindings/i2c/i2c-designware.txt     |   14 ++++++++++++++
 drivers/i2c/busses/i2c-designware-core.c           |    5 +++++
 drivers/i2c/busses/i2c-designware-core.h           |    1 +
 drivers/i2c/busses/i2c-designware-platdrv.c        |    9 +++++++++
 4 files changed, 29 insertions(+), 0 deletions(-)

diff --git a/Documentation/devicetree/bindings/i2c/i2c-designware.txt b/Documentation/devicetree/bindings/i2c/i2c-designware.txt
index e42a2ee..21fabe7 100644
--- a/Documentation/devicetree/bindings/i2c/i2c-designware.txt
+++ b/Documentation/devicetree/bindings/i2c/i2c-designware.txt
@@ -10,6 +10,9 @@ Recommended properties :
 
  - clock-frequency : desired I2C bus clock frequency in Hz.
 
+Optional properties :
+ - sda-hold-time : should contain the SDA hold time in nanoseconds.
+
 Example :
 
 	i2c@...00 {
@@ -20,3 +23,14 @@ Example :
 		interrupts = <11>;
 		clock-frequency = <400000>;
 	};
+
+	i2c@...0000 {
+		#address-cells = <1>;
+		#size-cells = <0>;
+		compatible = "snps,designware-i2c";
+		reg = <0x1120000 0x1000>;
+		interrupt-parent = <&ictl>;
+		interrupts = <12 1>;
+		clock-frequency = <400000>;
+		sda-hold-time = <300>;
+	};
diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
index 21fbb34..91d422c 100644
--- a/drivers/i2c/busses/i2c-designware-core.c
+++ b/drivers/i2c/busses/i2c-designware-core.c
@@ -67,6 +67,7 @@
 #define DW_IC_STATUS		0x70
 #define DW_IC_TXFLR		0x74
 #define DW_IC_RXFLR		0x78
+#define DW_IC_SDA_HOLD		0x7c
 #define DW_IC_TX_ABRT_SOURCE	0x80
 #define DW_IC_ENABLE_STATUS	0x9c
 #define DW_IC_COMP_PARAM_1	0xf4
@@ -332,6 +333,10 @@ int i2c_dw_init(struct dw_i2c_dev *dev)
 	dw_writel(dev, lcnt, DW_IC_FS_SCL_LCNT);
 	dev_dbg(dev->dev, "Fast-mode HCNT:LCNT = %d:%d\n", hcnt, lcnt);
 
+	/* Configure SDA Hold Time if required */
+	if (dev->sda_hold_time)
+		dw_writel(dev, dev->sda_hold_time, DW_IC_SDA_HOLD);
+
 	/* Configure Tx/Rx FIFO threshold levels */
 	dw_writel(dev, dev->tx_fifo_depth - 1, DW_IC_TX_TL);
 	dw_writel(dev, 0, DW_IC_RX_TL);
diff --git a/drivers/i2c/busses/i2c-designware-core.h b/drivers/i2c/busses/i2c-designware-core.h
index 9c1840e..33dfec3 100644
--- a/drivers/i2c/busses/i2c-designware-core.h
+++ b/drivers/i2c/busses/i2c-designware-core.h
@@ -88,6 +88,7 @@ struct dw_i2c_dev {
 	u32			master_cfg;
 	unsigned int		tx_fifo_depth;
 	unsigned int		rx_fifo_depth;
+	u32			sda_hold_time;
 };
 
 #define ACCESS_SWAP		0x00000001
diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index 8ec9133..589f414 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -34,6 +34,7 @@
 #include <linux/sched.h>
 #include <linux/err.h>
 #include <linux/interrupt.h>
+#include <linux/of.h>
 #include <linux/of_i2c.h>
 #include <linux/platform_device.h>
 #include <linux/pm.h>
@@ -120,6 +121,14 @@ static int dw_i2c_probe(struct platform_device *pdev)
 		return PTR_ERR(dev->clk);
 	clk_prepare_enable(dev->clk);
 
+	if (pdev->dev.of_node) {
+		u32 ht;
+		u32 ic_clk = dev->get_clk_rate_khz(dev);
+
+		of_property_read_u32(pdev->dev.of_node, "sda-hold-time", &ht);
+		dev->sda_hold_time = ((u64)ic_clk * ht + 500000) / 1000000;
+	}
+
 	dev->functionality =
 		I2C_FUNC_I2C |
 		I2C_FUNC_10BIT_ADDR |
-- 
1.7.1

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