i2c-designware: make SDA hold time configurable

This patch makes the SDA hold time configurable through device tree.
Signed-off-by: Christian Ruppert <christian.ruppert@abilis.com>
Signed-off-by: Pierrick Hascoet <pierrick.hascoet@abilis.com>
Acked-by: Vineet Gupta <vgupta@synopsys.com> for arch/arc bits
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Documentation/devicetree/bindings/i2c/i2c-designware.txt

@@ -10,6 +10,10 @@ Recommended properties :
 
  - clock-frequency : desired I2C bus clock frequency in Hz.
 
+Optional properties :
+ - i2c-sda-hold-time-ns : should contain the SDA hold time in nanoseconds.
+   This option is only supported in hardware blocks version 1.11a or newer.
+
 Example :
 
 	i2c@f0000 {
@@ -20,3 +24,14 @@ Example :
 		interrupts = <11>;
 		clock-frequency = <400000>;
 	};
+
+	i2c@1120000 {
+		#address-cells = <1>;
+		#size-cells = <0>;
+		compatible = "snps,designware-i2c";
+		reg = <0x1120000 0x1000>;
+		interrupt-parent = <&ictl>;
+		interrupts = <12 1>;
+		clock-frequency = <400000>;
+		i2c-sda-hold-time-ns = <300>;
+	};

arch/arc/boot/dts/abilis_tb100_dvk.dts

@@ -45,19 +45,19 @@ ethernet@FE100000 {
 		};
 
 		i2c0: i2c@FF120000 {
-			sda-hold-time = <432>;
+			i2c-sda-hold-time-ns = <432>;
 		};
 		i2c1: i2c@FF121000 {
-			sda-hold-time = <432>;
+			i2c-sda-hold-time-ns = <432>;
 		};
 		i2c2: i2c@FF122000 {
-			sda-hold-time = <432>;
+			i2c-sda-hold-time-ns = <432>;
 		};
 		i2c3: i2c@FF123000 {
-			sda-hold-time = <432>;
+			i2c-sda-hold-time-ns = <432>;
 		};
 		i2c4: i2c@FF124000 {
-			sda-hold-time = <432>;
+			i2c-sda-hold-time-ns = <432>;
 		};
 
 		leds {

arch/arc/boot/dts/abilis_tb101_dvk.dts

@@ -45,19 +45,19 @@ ethernet@FE100000 {
 		};
 
 		i2c0: i2c@FF120000 {
-			sda-hold-time = <432>;
+			i2c-sda-hold-time-ns = <432>;
 		};
 		i2c1: i2c@FF121000 {
-			sda-hold-time = <432>;
+			i2c-sda-hold-time-ns = <432>;
 		};
 		i2c2: i2c@FF122000 {
-			sda-hold-time = <432>;
+			i2c-sda-hold-time-ns = <432>;
 		};
 		i2c3: i2c@FF123000 {
-			sda-hold-time = <432>;
+			i2c-sda-hold-time-ns = <432>;
 		};
 		i2c4: i2c@FF124000 {
-			sda-hold-time = <432>;
+			i2c-sda-hold-time-ns = <432>;
 		};
 
 		leds {

drivers/i2c/busses/i2c-designware-core.c

@@ -67,9 +67,12 @@
 #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
+#define DW_IC_COMP_VERSION	0xf8
+#define DW_IC_SDA_HOLD_MIN_VERS	0x3131312A
 #define DW_IC_COMP_TYPE		0xfc
 #define DW_IC_COMP_TYPE_VALUE	0x44570140
 
@@ -332,6 +335,16 @@ 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) {
+		reg = dw_readl(dev, DW_IC_COMP_VERSION);
+		if (reg >= DW_IC_SDA_HOLD_MIN_VERS)
+			dw_writel(dev, dev->sda_hold_time, DW_IC_SDA_HOLD);
+		else
+			dev_warn(dev->dev,
+				"Hardware too old to adjust SDA hold time.");
+	}
+
 	/* 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);

drivers/i2c/busses/i2c-designware-core.h

@@ -90,6 +90,7 @@ struct dw_i2c_dev {
 	unsigned int		tx_fifo_depth;
 	unsigned int		rx_fifo_depth;
 	int			rx_outstanding;
+	u32			sda_hold_time;
 };
 
 #define ACCESS_SWAP		0x00000001

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>
@@ -115,6 +116,15 @@ 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 = 0;
+		u32 ic_clk = dev->get_clk_rate_khz(dev);
+
+		of_property_read_u32(pdev->dev.of_node,
+					"i2c-sda-hold-time-ns", &ht);
+		dev->sda_hold_time = ((u64)ic_clk * ht + 500000) / 1000000;
+	}
+
 	dev->functionality =
 		I2C_FUNC_I2C |
 		I2C_FUNC_10BIT_ADDR |