linux-kernel - [PATCH] hwmon: adm1275: Make sure we are reading enough data for different chips

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Message-Id: <20200708235306.3854404-1-linchuyuan@google.com>
Date:   Wed,  8 Jul 2020 23:53:06 +0000
From:   Chu Lin <linchuyuan@...gle.com>
To:     linux@...ck-us.net
Cc:     belgaied@...gle.com, jasonling@...gle.com, jdelvare@...e.com,
        linchuyuan@...gle.com, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org, zhongqil@...gle.com
Subject: [PATCH] hwmon: adm1275: Make sure we are reading enough data for
 different chips

Issue:
When binding adm1272 to the adm1275 driver, PEC error is reported.
See blow:
adm1275: probe of xxxx failed with error -74

Diagnosis:
Per the datasheet of adm1272 and adm1278 (www.analog.com),
PMON_CONFIG (0xd4) is 16bits wide. On the other hand,
PMON_CONFIG (0xd4) for adm1275 is 8bits wide.
The driver should not assume everything is 8bits wide and read only
8bits from it.

Solution:
if it is adm1272 or adm1278, use i2c_read_word. Else, use i2c_read_byte

Signed-off-by: Chu Lin <linchuyuan@...gle.com>
---
 drivers/hwmon/pmbus/adm1275.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/drivers/hwmon/pmbus/adm1275.c b/drivers/hwmon/pmbus/adm1275.c
index e25f541227da..a0d547d20358 100644
--- a/drivers/hwmon/pmbus/adm1275.c
+++ b/drivers/hwmon/pmbus/adm1275.c
@@ -472,6 +472,7 @@ static int adm1275_probe(struct i2c_client *client,
 	struct adm1275_data *data;
 	const struct i2c_device_id *mid;
 	const struct coefficients *coefficients;
+	s32 (*config_read_fn_ptr)(const struct i2c_client *client, u8 reg);
 	int vindex = -1, voindex = -1, cindex = -1, pindex = -1;
 	int tindex = -1;
 	u32 shunt;
@@ -510,14 +511,6 @@ static int adm1275_probe(struct i2c_client *client,
 			   "Device mismatch: Configured %s, detected %s\n",
 			   id->name, mid->name);
 
-	config = i2c_smbus_read_byte_data(client, ADM1275_PMON_CONFIG);
-	if (config < 0)
-		return config;
-
-	device_config = i2c_smbus_read_byte_data(client, ADM1275_DEVICE_CONFIG);
-	if (device_config < 0)
-		return device_config;
-
 	data = devm_kzalloc(&client->dev, sizeof(struct adm1275_data),
 			    GFP_KERNEL);
 	if (!data)
@@ -532,6 +525,21 @@ static int adm1275_probe(struct i2c_client *client,
 
 	data->id = mid->driver_data;
 
+	/* adm1272 and adm1278 supports temperature monitoring.  The config and device config
+	 * are 16bits wide for these two devices. On the other hand, other devices are 8 bits wide
+	 */
+	if (data->id == adm1272 || data->id == adm1278)
+		config_read_fn_ptr = &i2c_smbus_read_word_data;
+	else
+		config_read_fn_ptr = &i2c_smbus_read_byte_data;
+	config = config_read_fn_ptr(client, ADM1275_PMON_CONFIG);
+	if (config < 0)
+		return config;
+
+	device_config = config_read_fn_ptr(client, ADM1275_DEVICE_CONFIG);
+	if (device_config < 0)
+		return device_config;
+
 	info = &data->info;
 
 	info->pages = 1;
-- 
2.27.0.383.g050319c2ae-goog