[PATCH v2 1/3] hwmon: (pmbus) Introduce and use cached vout margins

[Mårten Lindahl <marten.lindahl@xxxxxxxx>]

When setting a new voltage the voltage boundaries are read every time to
check that the new voltage is within the proper range. Checking these
voltage boundaries consists of reading one of PMBUS_MFR_VOUT_MIN/
PMBUS_VOUT_MARGIN_LOW registers and then PMBUS_MFR_VOUT_MAX/
PMBUS_VOUT_MARGIN_HIGH together with writing the PMBUS_CLEAR_FAULTS
register.

Since these boundaries are never being changed, it can be cached and
thus saving unnecessary smbus transmissions.

Signed-off-by: Mårten Lindahl <marten.lindahl@xxxxxxxx>
---
 drivers/hwmon/pmbus/pmbus_core.c | 54 +++++++++++++++++++-------------
 1 file changed, 32 insertions(+), 22 deletions(-)

diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
index 02912022853d..478dda49a45f 100644
--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c
@@ -104,6 +104,9 @@ struct pmbus_data {
 
 	s16 currpage;	/* current page, -1 for unknown/unset */
 	s16 currphase;	/* current phase, 0xff for all, -1 for unknown/unset */
+
+	int vout_low[PMBUS_PAGES];	/* voltage low margin */
+	int vout_high[PMBUS_PAGES];	/* voltage high margin */
 };
 
 struct pmbus_debugfs_entry {
@@ -2667,34 +2670,41 @@ static int pmbus_regulator_set_voltage(struct regulator_dev *rdev, int min_uv,
 		.data = -1,
 	};
 	int val = DIV_ROUND_CLOSEST(min_uv, 1000); /* convert to mV */
-	int low, high;
 
 	*selector = 0;
 
-	if (pmbus_check_word_register(client, s.page, PMBUS_MFR_VOUT_MIN))
-		s.data = _pmbus_read_word_data(client, s.page, 0xff, PMBUS_MFR_VOUT_MIN);
-	if (s.data < 0) {
-		s.data = _pmbus_read_word_data(client, s.page, 0xff, PMBUS_VOUT_MARGIN_LOW);
-		if (s.data < 0)
-			return s.data;
-	}
-	low = pmbus_reg2data(data, &s);
-
-	s.data = -1;
-	if (pmbus_check_word_register(client, s.page, PMBUS_MFR_VOUT_MAX))
-		s.data = _pmbus_read_word_data(client, s.page, 0xff, PMBUS_MFR_VOUT_MAX);
-	if (s.data < 0) {
-		s.data = _pmbus_read_word_data(client, s.page, 0xff, PMBUS_VOUT_MARGIN_HIGH);
-		if (s.data < 0)
-			return s.data;
+	if (!data->vout_low[s.page]) {
+		if (pmbus_check_word_register(client, s.page, PMBUS_MFR_VOUT_MIN))
+			s.data = _pmbus_read_word_data(client, s.page, 0xff,
+						       PMBUS_MFR_VOUT_MIN);
+		if (s.data < 0) {
+			s.data = _pmbus_read_word_data(client, s.page, 0xff,
+						       PMBUS_VOUT_MARGIN_LOW);
+			if (s.data < 0)
+				return s.data;
+		}
+		data->vout_low[s.page] = pmbus_reg2data(data, &s);
+	}
+
+	if (!data->vout_high[s.page]) {
+		s.data = -1;
+		if (pmbus_check_word_register(client, s.page, PMBUS_MFR_VOUT_MAX))
+			s.data = _pmbus_read_word_data(client, s.page, 0xff,
+						       PMBUS_MFR_VOUT_MAX);
+		if (s.data < 0) {
+			s.data = _pmbus_read_word_data(client, s.page, 0xff,
+						       PMBUS_VOUT_MARGIN_HIGH);
+			if (s.data < 0)
+				return s.data;
+		}
+		data->vout_high[s.page] = pmbus_reg2data(data, &s);
 	}
-	high = pmbus_reg2data(data, &s);
 
 	/* Make sure we are within margins */
-	if (low > val)
-		val = low;
-	if (high < val)
-		val = high;
+	if (data->vout_low[s.page] > val)
+		val = data->vout_low[s.page];
+	if (data->vout_high[s.page] < val)
+		val = data->vout_high[s.page];
 
 	val = pmbus_data2reg(data, &s, val);
 
-- 
2.30.2