From ddf55be668a5e5a22d4b7729e7ba92d928983168 Mon Sep 17 00:00:00 2001
From: Zhang Ying-22455 <ying.zhang22455@nxp.com>
Date: Fri, 1 Dec 2017 15:59:28 +0800
Subject: [PATCH] i2c: imx: implement bus recovery with gpio for Layerscape

Based on the I2C specification, if the data line (SDA) is stuck low,
the master should send nine clock pulses. The I2C slave device that
held the bus low should release it sometime within those nine clocks.

Because pinctrl is not supported on Layerscape, current bus recovery
is not avalible for Layerscape. This patch uses an open drain GPIO
pin to connect to the IICx_SCL to drive nine clock pulses to unlock
the I2C bus.

Signed-off-by: Zhang Ying-22455 <ying.zhang22455@nxp.com>
---
 drivers/i2c/busses/i2c-imx.c | 190 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 188 insertions(+), 2 deletions(-)

--- a/drivers/i2c/busses/i2c-imx.c
+++ b/drivers/i2c/busses/i2c-imx.c
@@ -39,12 +39,18 @@
 #include <linux/of.h>
 #include <linux/of_device.h>
 #include <linux/of_dma.h>
+#include <linux/of_gpio.h>
 #include <linux/pinctrl/consumer.h>
 #include <linux/platform_data/i2c-imx.h>
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
+#include <linux/gpio.h>
+#include <linux/of_address.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/libata.h>
 
 /* This will be the driver name the kernel reports */
 #define DRIVER_NAME "imx-i2c"
@@ -110,6 +116,54 @@
 
 #define I2C_PM_TIMEOUT		10 /* ms */
 
+enum pinmux_endian_type {
+	BIG_ENDIAN,
+	LITTLE_ENDIAN,
+};
+
+struct pinmux_cfg {
+	enum pinmux_endian_type endian; /* endian of RCWPMUXCR0 */
+	u32 pmuxcr_offset;
+	u32 pmuxcr_set_bit;		    /* pin mux of RCWPMUXCR0 */
+};
+
+static struct pinmux_cfg ls1012a_pinmux_cfg = {
+	.endian = BIG_ENDIAN,
+	.pmuxcr_offset = 0x430,
+	.pmuxcr_set_bit = 0x10,
+};
+
+static struct pinmux_cfg ls1043a_pinmux_cfg = {
+	.endian = BIG_ENDIAN,
+	.pmuxcr_offset = 0x40C,
+	.pmuxcr_set_bit = 0x10,
+};
+
+static struct pinmux_cfg ls1046a_pinmux_cfg = {
+	.endian = BIG_ENDIAN,
+	.pmuxcr_offset = 0x40C,
+	.pmuxcr_set_bit = 0x80000000,
+};
+
+static const struct of_device_id pinmux_of_match[] = {
+	{ .compatible = "fsl,ls1012a-vf610-i2c", .data = &ls1012a_pinmux_cfg},
+	{ .compatible = "fsl,ls1043a-vf610-i2c", .data = &ls1043a_pinmux_cfg},
+	{ .compatible = "fsl,ls1046a-vf610-i2c", .data = &ls1046a_pinmux_cfg},
+	{},
+};
+MODULE_DEVICE_TABLE(of, pinmux_of_match);
+
+/* The SCFG, Supplemental Configuration Unit, provides SoC specific
+ * configuration and status registers for the device. There is a
+ * SDHC IO VSEL control register on SCFG for some platforms. It's
+ * used to support SDHC IO voltage switching.
+ */
+static const struct of_device_id scfg_device_ids[] = {
+	{ .compatible = "fsl,ls1012a-scfg", },
+	{ .compatible = "fsl,ls1043a-scfg", },
+	{ .compatible = "fsl,ls1046a-scfg", },
+	{}
+};
 /*
  * sorted list of clock divider, register value pairs
  * taken from table 26-5, p.26-9, Freescale i.MX
@@ -205,6 +259,12 @@ struct imx_i2c_struct {
 	struct pinctrl_state *pinctrl_pins_gpio;
 
 	struct imx_i2c_dma	*dma;
+	int			layerscape_bus_recover;
+	int 			gpio;
+	int			need_set_pmuxcr;
+	int			pmuxcr_set;
+	int			pmuxcr_endian;
+	void __iomem		*pmuxcr_addr;
 };
 
 static const struct imx_i2c_hwdata imx1_i2c_hwdata = {
@@ -951,6 +1011,78 @@ static int i2c_imx_read(struct imx_i2c_s
 	return 0;
 }
 
+/*
+ * Based on the I2C specification, if the data line (SDA) is
+ * stuck low, the master should send nine  * clock pulses.
+ * The I2C slave device that held the bus low should release it
+ * sometime within  * those nine clocks. Due to this erratum,
+ * the I2C controller cannot generate nine clock pulses.
+ */
+static int i2c_imx_recovery_for_layerscape(struct imx_i2c_struct *i2c_imx)
+{
+	u32 pmuxcr = 0;
+	int ret;
+	unsigned int i, temp;
+
+	/* configure IICx_SCL/GPIO pin as a GPIO */
+	if (i2c_imx->need_set_pmuxcr == 1) {
+		pmuxcr = ioread32be(i2c_imx->pmuxcr_addr);
+		if (i2c_imx->pmuxcr_endian == BIG_ENDIAN)
+			iowrite32be(i2c_imx->pmuxcr_set|pmuxcr,
+				    i2c_imx->pmuxcr_addr);
+		else
+			iowrite32(i2c_imx->pmuxcr_set|pmuxcr,
+				  i2c_imx->pmuxcr_addr);
+	}
+
+	ret = gpio_request(i2c_imx->gpio, i2c_imx->adapter.name);
+	if (ret) {
+		dev_err(&i2c_imx->adapter.dev,
+			"can't get gpio: %d\n", ret);
+		return ret;
+	}
+
+	/* Configure GPIO pin as an output and open drain. */
+	gpio_direction_output(i2c_imx->gpio, 1);
+	udelay(10);
+
+	/* Write data to generate 9 pulses */
+	for (i = 0; i < 9; i++) {
+		gpio_set_value(i2c_imx->gpio, 1);
+		udelay(10);
+		gpio_set_value(i2c_imx->gpio, 0);
+		udelay(10);
+	}
+	/* ensure that the last level sent is always high */
+	gpio_set_value(i2c_imx->gpio, 1);
+
+	/*
+	 * Set I2Cx_IBCR = 0h00 to generate a STOP and then
+	 * set I2Cx_IBCR = 0h80 to reset
+	 */
+	temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
+	temp &= ~(I2CR_MSTA | I2CR_MTX);
+	imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
+
+	/* Restore the saved value of the register SCFG_RCWPMUXCR0 */
+	if (i2c_imx->need_set_pmuxcr == 1) {
+		if (i2c_imx->pmuxcr_endian == BIG_ENDIAN)
+			iowrite32be(pmuxcr, i2c_imx->pmuxcr_addr);
+		else
+			iowrite32(pmuxcr, i2c_imx->pmuxcr_addr);
+	}
+	/*
+	 * Set I2C_IBSR[IBAL] to clear the IBAL bit if-
+	 * I2C_IBSR[IBAL] = 1
+	 */
+	temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2SR);
+	if (temp & I2SR_IAL) {
+		temp &= ~I2SR_IAL;
+		imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2SR);
+	}
+	return 0;
+}
+
 static int i2c_imx_xfer(struct i2c_adapter *adapter,
 						struct i2c_msg *msgs, int num)
 {
@@ -973,8 +1105,13 @@ static int i2c_imx_xfer(struct i2c_adapt
 	 * before switching to master mode and attempting a Start cycle
 	 */
 	result =  i2c_imx_bus_busy(i2c_imx, 0);
-	if (result)
-		goto out;
+	if (result) {
+		/* timeout */
+		if ((result == -ETIMEDOUT) && (i2c_imx->layerscape_bus_recover == 1))
+			i2c_imx_recovery_for_layerscape(i2c_imx);
+		else
+			goto out;
+	}
 
 	result = pm_runtime_get_sync(i2c_imx->adapter.dev.parent);
 	if (result < 0)
@@ -1121,6 +1258,50 @@ static int i2c_imx_init_recovery_info(st
 	return 0;
 }
 
+/*
+ * switch SCL and SDA to their GPIO function and do some bitbanging
+ * for bus recovery.
+ * There are platforms such as Layerscape that don't support pinctrl, so add
+ * workaround for layerscape, it has no effect for other platforms.
+ */
+static int i2c_imx_init_recovery_for_layerscape(
+		struct imx_i2c_struct *i2c_imx,
+		struct platform_device *pdev)
+{
+	const struct of_device_id *of_id;
+	struct device_node *np		= pdev->dev.of_node;
+	struct pinmux_cfg		*pinmux_cfg;
+	struct device_node *scfg_node;
+	void __iomem *scfg_base = NULL;
+
+	i2c_imx->gpio = of_get_named_gpio(np, "scl-gpios", 0);
+	if (!gpio_is_valid(i2c_imx->gpio)) {
+		dev_info(&pdev->dev, "scl-gpios not found\n");
+		return 0;
+	}
+	pinmux_cfg = devm_kzalloc(&pdev->dev, sizeof(*pinmux_cfg), GFP_KERNEL);
+	if (!pinmux_cfg)
+		return -ENOMEM;
+
+	i2c_imx->need_set_pmuxcr = 0;
+	of_id = of_match_node(pinmux_of_match, np);
+	if (of_id) {
+		pinmux_cfg = (struct pinmux_cfg *)of_id->data;
+		i2c_imx->pmuxcr_endian = pinmux_cfg->endian;
+		i2c_imx->pmuxcr_set = pinmux_cfg->pmuxcr_set_bit;
+		scfg_node = of_find_matching_node(NULL, scfg_device_ids);
+		if (scfg_node) {
+			scfg_base = of_iomap(scfg_node, 0);
+			if (scfg_base) {
+				i2c_imx->pmuxcr_addr = scfg_base + pinmux_cfg->pmuxcr_offset;
+				i2c_imx->need_set_pmuxcr = 1;
+			}
+		}
+	}
+	i2c_imx->layerscape_bus_recover = 1;
+	return 0;
+}
+
 static u32 i2c_imx_func(struct i2c_adapter *adapter)
 {
 	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL
@@ -1245,8 +1426,13 @@ static int i2c_imx_probe(struct platform
 			i2c_imx, IMX_I2C_I2CR);
 	imx_i2c_write_reg(i2c_imx->hwdata->i2sr_clr_opcode, i2c_imx, IMX_I2C_I2SR);
 
+#ifdef CONFIG_ARCH_LAYERSCAPE
+	/* Init optional bus recovery for layerscape */
+	ret = i2c_imx_init_recovery_for_layerscape(i2c_imx, pdev);
+#else
 	/* Init optional bus recovery function */
 	ret = i2c_imx_init_recovery_info(i2c_imx, pdev);
+#endif
 	/* Give it another chance if pinctrl used is not ready yet */
 	if (ret == -EPROBE_DEFER)
 		goto clk_notifier_unregister;