[PATCH] i2c-designware: Interrupt sharing and SDA hold time

[Christian Ruppert <christian.ruppert-ux6zf3SgZrrQT0dZR+AlfA@public.gmane.org>]

This patch implements interrupt sharing and SDA hold time configuration in
the designware i2c driver. Both functions are enabled through platform data
or device tree. Tested with Linux-3.8rc4 (Synopsys ARC port, see
https://github.com/foss-for-synopsys-dwc-arc-processors/linux/commits/arc-3.8-baseline).

Signed-off-by: Christian Ruppert <christian.ruppert-ux6zf3SgZrrQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Pierrick Hascoet <pierrick.hascoet-ux6zf3SgZrrQT0dZR+AlfA@public.gmane.org>
---
 .../devicetree/bindings/i2c/i2c-designware.txt     |   18 ++++++++++
 drivers/i2c/busses/i2c-designware-core.c           |    6 +++
 drivers/i2c/busses/i2c-designware-core.h           |    2 +
 drivers/i2c/busses/i2c-designware-platdrv.c        |   34 +++++++++++++++++++-
 include/linux/i2c/i2c-designware.h                 |   13 +++++++
 5 files changed, 72 insertions(+), 1 deletions(-)
 create mode 100644 include/linux/i2c/i2c-designware.h

diff --git a/Documentation/devicetree/bindings/i2c/i2c-designware.txt b/Documentation/devicetree/bindings/i2c/i2c-designware.txt
index e42a2ee..474386b 100644
--- a/Documentation/devicetree/bindings/i2c/i2c-designware.txt
+++ b/Documentation/devicetree/bindings/i2c/i2c-designware.txt
@@ -10,6 +10,12 @@ Recommended properties :
 
  - clock-frequency : desired I2C bus clock frequency in Hz.
 
+Optional properties :
+ - interrupts-shared : If this property is present, the interrupt line is
+   considered shared with other devices.
+ - sda-hold-time : If this property is present, the register SDA_HOLD will
+   be initialised with its value.
+
 Example :
 
 	i2c@f0000 {
@@ -20,3 +26,15 @@ 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>;
+		interrupts-shared;
+		clock-frequency = <400000>;
+		sda-hold-time = <0x64>;
+	};
diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
index cbba7db..36ba0b5 100644
--- a/drivers/i2c/busses/i2c-designware-core.c
+++ b/drivers/i2c/busses/i2c-designware-core.c
@@ -34,6 +34,7 @@
 #include <linux/io.h>
 #include <linux/pm_runtime.h>
 #include <linux/delay.h>
+#include <linux/i2c/i2c-designware.h>
 #include "i2c-designware-core.h"
 
 /*
@@ -66,6 +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_COMP_PARAM_1	0xf4
 #define DW_IC_COMP_TYPE		0xfc
@@ -309,6 +311,10 @@ 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->pdat_flags & I2C_DW_PDAT_FLAGS_SET_HOLDTIME)
+		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..ef20477 100644
--- a/drivers/i2c/busses/i2c-designware-core.h
+++ b/drivers/i2c/busses/i2c-designware-core.h
@@ -88,6 +88,8 @@ struct dw_i2c_dev {
 	u32			master_cfg;
 	unsigned int		tx_fifo_depth;
 	unsigned int		rx_fifo_depth;
+	u32			sda_hold_time;
+	unsigned int		pdat_flags;
 };
 
 #define ACCESS_SWAP		0x00000001
diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index 343357a..2ad2da3 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -34,11 +34,13 @@
 #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>
 #include <linux/io.h>
 #include <linux/slab.h>
+#include <linux/i2c/i2c-designware.h>
 #include "i2c-designware-core.h"
 
 static struct i2c_algorithm i2c_dw_algo = {
@@ -56,6 +58,28 @@ static int dw_i2c_probe(struct platform_device *pdev)
 	struct i2c_adapter *adap;
 	struct resource *mem, *ioarea;
 	int irq, r;
+	unsigned long irqf;
+	struct i2c_designware_platform_data *pdat = pdev->dev.platform_data;
+
+	if ((!pdat) && pdev->dev.of_node) {
+		struct device_node *node = pdev->dev.of_node;
+
+		pdat = kmalloc(sizeof(struct i2c_designware_platform_data),
+				GFP_KERNEL);
+		if (!pdat)
+			return -ENOMEM;
+
+		pdat->flags = 0;
+
+		if (of_get_property(node, "interrupts-shared", NULL))
+			pdat->flags |= I2C_DW_PDAT_FLAGS_SHARE_IRQ;
+
+		if (!of_property_read_u32(node, "sda-hold-time",
+					&pdat->sda_hold_time))
+			pdat->flags |= I2C_DW_PDAT_FLAGS_SET_HOLDTIME;
+
+		pdev->dev.platform_data = pdat;
+	}
 
 	/* NOTE: driver uses the static register mapping */
 	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
@@ -120,12 +144,20 @@ static int dw_i2c_probe(struct platform_device *pdev)
 		dev->tx_fifo_depth = ((param1 >> 16) & 0xff) + 1;
 		dev->rx_fifo_depth = ((param1 >> 8)  & 0xff) + 1;
 	}
+	dev->sda_hold_time = pdat->sda_hold_time;
+	dev->pdat_flags = pdat->flags;
+
 	r = i2c_dw_init(dev);
 	if (r)
 		goto err_iounmap;
 
 	i2c_dw_disable_int(dev);
-	r = request_irq(dev->irq, i2c_dw_isr, IRQF_DISABLED, pdev->name, dev);
+
+	irqf = IRQF_DISABLED;
+	if (dev->pdat_flags & I2C_DW_PDAT_FLAGS_SHARE_IRQ)
+		irqf |= IRQF_SHARED;
+
+	r = request_irq(dev->irq, i2c_dw_isr, irqf, pdev->name, dev);
 	if (r) {
 		dev_err(&pdev->dev, "failure requesting irq %i\n", dev->irq);
 		goto err_iounmap;
diff --git a/include/linux/i2c/i2c-designware.h b/include/linux/i2c/i2c-designware.h
new file mode 100644
index 0000000..ea8192a
--- /dev/null
+++ b/include/linux/i2c/i2c-designware.h
@@ -0,0 +1,13 @@
+#ifndef __I2C_DESIGNWARE_H__
+#define __I2C_DESIGNWARE_H__
+
+#include <linux/platform_device.h>
+
+struct i2c_designware_platform_data {
+	unsigned int flags;
+#define I2C_DW_PDAT_FLAGS_SHARE_IRQ    (1L<<0)
+#define I2C_DW_PDAT_FLAGS_SET_HOLDTIME (1L<<1)
+	u32          sda_hold_time;
+};
+
+#endif /* __I2C_DESIGNWARE_H__ */
-- 
1.7.1