Reinvent I2C ops

Do not use the global platform_i2c_transfer() function that can only be
implemented by a single driver. Instead, make a `struct device` aware
transfer() function the only interface function for I2C controller dri-
vers to implement.

To not force the slave device drivers to be implemented either above
generic I2C or specialized SMBus operations, we support SMBus control-
lers in the slave device interface too.

We start with four simple slave functions: i2c_readb(), i2c_writeb(),
i2c_readb_at() and i2c_writeb_at(). They are all compatible to respec-
tive SMBus functions. But we keep aliases because it would be weird to
force e.g. an I2C EEPROM driver to call smbus_read_byte().

Change-Id: I98386f91bf4799ba3df84ec8bc0f64edd4142818
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/20846
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

3 files changed, 26 insertions, 7 deletions

diff --git a/src/soc/intel/common/block/i2c/i2c.c b/src/soc/intel/common/block/i2c/i2c.c
index aeb6d8f2ed..625bb991d4 100644
--- a/src/soc/intel/common/block/i2c/i2c.c
+++ b/src/soc/intel/common/block/i2c/i2c.c
@@ -150,8 +150,14 @@ static void lpss_i2c_acpi_fill_ssdt(struct device *dev)
 	acpigen_pop_len();
 }
 
-static struct i2c_bus_operations i2c_bus_ops = {
-	.dev_to_bus			= &lpss_i2c_dev_to_bus,
+static int lpss_i2c_dev_transfer(struct device *dev,
+				 const struct i2c_msg *msg, size_t count)
+{
+	return lpss_i2c_transfer(lpss_i2c_dev_to_bus(dev), msg, count);
+}
+
+static const struct i2c_bus_operations i2c_bus_ops = {
+	.transfer = lpss_i2c_dev_transfer,
 };
 
 static struct device_operations i2c_dev_ops = {
diff --git a/src/soc/intel/common/block/i2c/lpss_i2c.c b/src/soc/intel/common/block/i2c/lpss_i2c.c
index 868a6ad300..7db3fe9668 100644
--- a/src/soc/intel/common/block/i2c/lpss_i2c.c
+++ b/src/soc/intel/common/block/i2c/lpss_i2c.c
@@ -258,7 +258,7 @@ static int lpss_i2c_wait_for_bus_idle(struct lpss_i2c_regs *regs)
 
 /* Transfer one byte of one segment, sending stop bit if requested */
 static int lpss_i2c_transfer_byte(struct lpss_i2c_regs *regs,
-				  struct i2c_msg *segment,
+				  const struct i2c_msg *segment,
 				  size_t byte, int send_stop)
 {
 	struct stopwatch sw;
@@ -297,16 +297,15 @@ static int lpss_i2c_transfer_byte(struct lpss_i2c_regs *regs,
 	return 0;
 }
 
-/* Global I2C bus handler, defined in include/i2c.h */
-int platform_i2c_transfer(unsigned int bus, struct i2c_msg *segments,
-			  int count)
+int lpss_i2c_transfer(unsigned int bus,
+		      const struct i2c_msg *segments, size_t count)
 {
 	struct stopwatch sw;
 	struct lpss_i2c_regs *regs;
 	size_t byte;
 	int ret = -1;
 
-	if (count <= 0 || !segments)
+	if (count == 0 || !segments)
 		return -1;
 
 	regs = (struct lpss_i2c_regs *)lpss_i2c_base_address(bus);
@@ -396,6 +395,12 @@ out:
 	return ret;
 }
 
+/* Global I2C bus handler, defined in include/device/i2c_simple.h */
+int platform_i2c_transfer(unsigned int bus, struct i2c_msg *msg, int count)
+{
+	return lpss_i2c_transfer(bus, msg, count < 0 ? 0 : count);
+}
+
 static int lpss_i2c_set_speed_config(unsigned int bus,
 				const struct lpss_i2c_speed_config *config)
 {
diff --git a/src/soc/intel/common/block/i2c/lpss_i2c.h b/src/soc/intel/common/block/i2c/lpss_i2c.h
index 2cb3d5ed52..72341621c0 100644
--- a/src/soc/intel/common/block/i2c/lpss_i2c.h
+++ b/src/soc/intel/common/block/i2c/lpss_i2c.h
@@ -89,3 +89,11 @@ int lpss_i2c_gen_speed_config(struct lpss_i2c_regs *regs,
 					enum i2c_speed speed,
 					const struct lpss_i2c_bus_config *bcfg,
 					struct lpss_i2c_speed_config *config);
+
+/*
+ * Process given I2C segments in a single transfer
+ * Return value:
+ * -1 = failure
+ *  0 = success
+ */
+int lpss_i2c_transfer(unsigned int bus, const struct i2c_msg *, size_t count);