i2c: designware: Add Baikal-T1 System I2C support

Baikal-T1 System Controller is equipped with a dedicated I2C Controller
which functionality is based on the DW APB I2C IP-core, the only
difference in a way it' registers are accessed. There are three access
register provided in the System Controller registers map, which indirectly
address the normal DW APB I2C registers space. So in order to have the
Baikal-T1 System I2C Controller supported by the common DW APB I2C driver
we created a dedicated Dw I2C controller model quirk, which retrieves the
syscon regmap from the parental dt node and creates a new regmap based on
it.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

1 files changed, 76 insertions, 2 deletions

diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index 9d467fa0e163..b55c730f28cf 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -18,6 +18,7 @@
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_data/i2c-designware.h>
@@ -25,6 +26,7 @@
 #include <linux/pm.h>
 #include <linux/pm_runtime.h>
 #include <linux/property.h>
+#include <linux/regmap.h>
 #include <linux/reset.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
@@ -58,6 +60,63 @@ MODULE_DEVICE_TABLE(acpi, dw_i2c_acpi_match);
 #endif
 
 #ifdef CONFIG_OF
+#define BT1_I2C_CTL			0x100
+#define BT1_I2C_CTL_ADDR_MASK		GENMASK(7, 0)
+#define BT1_I2C_CTL_WR			BIT(8)
+#define BT1_I2C_CTL_GO			BIT(31)
+#define BT1_I2C_DI			0x104
+#define BT1_I2C_DO			0x108
+
+static int bt1_i2c_read(void *context, unsigned int reg, unsigned int *val)
+{
+	struct dw_i2c_dev *dev = context;
+	int ret;
+
+	/*
+	 * Note these methods shouldn't ever fail because the system controller
+	 * registers are memory mapped. We check the return value just in case.
+	 */
+	ret = regmap_write(dev->sysmap, BT1_I2C_CTL,
+			   BT1_I2C_CTL_GO | (reg & BT1_I2C_CTL_ADDR_MASK));
+	if (ret)
+		return ret;
+
+	return regmap_read(dev->sysmap, BT1_I2C_DO, val);
+}
+
+static int bt1_i2c_write(void *context, unsigned int reg, unsigned int val)
+{
+	struct dw_i2c_dev *dev = context;
+	int ret;
+
+	ret = regmap_write(dev->sysmap, BT1_I2C_DI, val);
+	if (ret)
+		return ret;
+
+	return regmap_write(dev->sysmap, BT1_I2C_CTL,
+		BT1_I2C_CTL_GO | BT1_I2C_CTL_WR | (reg & BT1_I2C_CTL_ADDR_MASK));
+}
+
+static struct regmap_config bt1_i2c_cfg = {
+	.reg_bits = 32,
+	.val_bits = 32,
+	.reg_stride = 4,
+	.fast_io = true,
+	.reg_read = bt1_i2c_read,
+	.reg_write = bt1_i2c_write,
+	.max_register = DW_IC_COMP_TYPE,
+};
+
+static int bt1_i2c_request_regs(struct dw_i2c_dev *dev)
+{
+	dev->sysmap = syscon_node_to_regmap(dev->dev->of_node->parent);
+	if (IS_ERR(dev->sysmap))
+		return PTR_ERR(dev->sysmap);
+
+	dev->map = devm_regmap_init(dev->dev, NULL, dev, &bt1_i2c_cfg);
+	return PTR_ERR_OR_ZERO(dev->map);
+}
+
 #define MSCC_ICPU_CFG_TWI_DELAY		0x0
 #define MSCC_ICPU_CFG_TWI_DELAY_ENABLE	BIT(0)
 #define MSCC_ICPU_CFG_TWI_SPIKE_FILTER	0x4
@@ -90,10 +149,16 @@ static int dw_i2c_of_configure(struct platform_device *pdev)
 static const struct of_device_id dw_i2c_of_match[] = {
 	{ .compatible = "snps,designware-i2c", },
 	{ .compatible = "mscc,ocelot-i2c", .data = (void *)MODEL_MSCC_OCELOT },
+	{ .compatible = "baikal,bt1-sys-i2c", .data = (void *)MODEL_BAIKAL_BT1 },
 	{},
 };
 MODULE_DEVICE_TABLE(of, dw_i2c_of_match);
 #else
+static int bt1_i2c_request_regs(struct dw_i2c_dev *dev)
+{
+	return -ENODEV;
+}
+
 static inline int dw_i2c_of_configure(struct platform_device *pdev)
 {
 	return -ENODEV;
@@ -111,10 +176,19 @@ static void dw_i2c_plat_pm_cleanup(struct dw_i2c_dev *dev)
 static int dw_i2c_plat_request_regs(struct dw_i2c_dev *dev)
 {
 	struct platform_device *pdev = to_platform_device(dev->dev);
+	int ret;
 
-	dev->base = devm_platform_ioremap_resource(pdev, 0);
+	switch (dev->flags & MODEL_MASK) {
+	case MODEL_BAIKAL_BT1:
+		ret = bt1_i2c_request_regs(dev);
+		break;
+	default:
+		dev->base = devm_platform_ioremap_resource(pdev, 0);
+		ret = PTR_ERR_OR_ZERO(dev->base);
+		break;
+	}
 
-	return PTR_ERR_OR_ZERO(dev->base);
+	return ret;
 }
 
 static int dw_i2c_plat_probe(struct platform_device *pdev)