[U-Boot] [PATCH 2/6] power: Explicitly select pmic device's bus

[Leela Krishna Amudala]

The current pmic i2c code assumes the current i2c bus is
the same as the pmic device's bus. There is nothing ensuring
that to be true. Therefore, select the proper bus before performing
a transaction.

Signed-off-by: Aaron Durbin <adurbin at chromium.org>
Signed-off-by: Simon Glass <sjg at chromium.org>
Signed-off-by: Leela Krishna Amudala <l.krishna at samsung.com>
Reviewed-by: Doug Anderson <dianders at google.com>
---
 drivers/power/power_i2c.c |   62 +++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 57 insertions(+), 5 deletions(-)

diff --git a/drivers/power/power_i2c.c b/drivers/power/power_i2c.c
index 47c606f..c22e01f 100644
--- a/drivers/power/power_i2c.c
+++ b/drivers/power/power_i2c.c
@@ -16,9 +16,45 @@
 #include <i2c.h>
 #include <compiler.h>
 
+static int pmic_select(struct pmic *p)
+{
+	int ret, old_bus;
+
+	old_bus = i2c_get_bus_num();
+	if (old_bus != p->bus) {
+		debug("%s: Select bus %d\n", __func__, p->bus);
+		ret = i2c_set_bus_num(p->bus);
+		if (ret) {
+			debug("%s: Cannot select pmic %s, err %d\n",
+			      __func__, p->name, ret);
+			return -1;
+		}
+	}
+
+	return old_bus;
+}
+
+static int pmic_deselect(int old_bus)
+{
+	int ret;
+
+	if (old_bus != i2c_get_bus_num()) {
+		ret = i2c_set_bus_num(old_bus);
+		debug("%s: Select bus %d\n", __func__, old_bus);
+		if (ret) {
+			debug("%s: Cannot restore i2c bus, err %d\n",
+			      __func__, ret);
+			return -1;
+		}
+	}
+
+	return 0;
+}
+
 int pmic_reg_write(struct pmic *p, u32 reg, u32 val)
 {
 	unsigned char buf[4] = { 0 };
+	int ret, old_bus;
 
 	if (check_reg(p, reg))
 		return -1;
@@ -52,23 +88,33 @@ int pmic_reg_write(struct pmic *p, u32 reg, u32 val)
 		return -1;
 	}
 
-	if (i2c_write(pmic_i2c_addr, reg, 1, buf, pmic_i2c_tx_num))
+	old_bus = pmic_select(p);
+	if (old_bus < 0)
 		return -1;
 
-	return 0;
+	ret = i2c_write(pmic_i2c_addr, reg, 1, buf, pmic_i2c_tx_num);
+	pmic_deselect(old_bus);
+	return ret;
 }
 
 int pmic_reg_read(struct pmic *p, u32 reg, u32 *val)
 {
 	unsigned char buf[4] = { 0 };
 	u32 ret_val = 0;
+	int ret, old_bus;
 
 	if (check_reg(p, reg))
 		return -1;
 
-	if (i2c_read(pmic_i2c_addr, reg, 1, buf, pmic_i2c_tx_num))
+	old_bus = pmic_select(p);
+	if (old_bus < 0)
 		return -1;
 
+	ret = i2c_read(pmic_i2c_addr, reg, 1, buf, pmic_i2c_tx_num);
+	pmic_deselect(old_bus);
+	if (ret)
+		return ret;
+
 	switch (pmic_i2c_tx_num) {
 	case 3:
 		if (p->sensor_byte_order == PMIC_SENSOR_BYTE_ORDER_BIG)
@@ -117,9 +163,15 @@ int pmic_reg_update(struct pmic *p, int reg, uint regval)
 
 int pmic_probe(struct pmic *p)
 {
-	i2c_set_bus_num(p->bus);
+	int ret, old_bus;
+
+	old_bus = pmic_select(p);
+	if (old_bus < 0)
+		return -1;
 	debug("Bus: %d PMIC:%s probed!\n", p->bus, p->name);
-	if (i2c_probe(pmic_i2c_addr)) {
+	ret = i2c_probe(pmic_i2c_addr);
+	pmic_deselect(old_bus);
+	if (ret) {
 		printf("Can't find PMIC:%s\n", p->name);
 		return -1;
 	}
-- 
1.7.10.4