linux-kernel - [PATCH v2] hwmon: adm1275: Make sure we are reading enough data for different chips

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Message-Id: <20200709040612.3977094-1-linchuyuan@google.com>
Date:   Thu,  9 Jul 2020 04:06:12 +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 v2] hwmon: adm1275: Make sure we are reading enough data for
 different chips

Issue:
When PEC is enabled, binding adm1272 to the adm1275 would
fail due to PEC error. See below:
adm1275: probe of xxxx failed with error -74

Diagnosis:
Per the datasheet of adm1272, adm1278, adm1293 and amd1294,
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, adm1278, adm1293 and adm1294, use i2c_read_word.
Else, use i2c_read_byte

Testing:
Binding adm1272 to the driver.
The change is only tested on adm1272.

Signed-off-by: Chu Lin <linchuyuan@...gle.com>
---

ChangeLog v1 -> v2
  - Rename config_read_fn_ptr to config_read_fn
  - Move config_read_fn to the first line as it is the longest
    variable declaration
  - Include adm1293 and adm1294
  - Remove the inline comment as I think the purpose is obvious


 drivers/hwmon/pmbus/adm1275.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/hwmon/pmbus/adm1275.c b/drivers/hwmon/pmbus/adm1275.c
index e25f541227da..19317575d1c6 100644
--- a/drivers/hwmon/pmbus/adm1275.c
+++ b/drivers/hwmon/pmbus/adm1275.c
@@ -465,6 +465,7 @@ MODULE_DEVICE_TABLE(i2c, adm1275_id);
 static int adm1275_probe(struct i2c_client *client,
 			 const struct i2c_device_id *id)
 {
+	s32 (*config_read_fn)(const struct i2c_client *client, u8 reg);
 	u8 block_buffer[I2C_SMBUS_BLOCK_MAX + 1];
 	int config, device_config;
 	int ret;
@@ -510,11 +511,16 @@ 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 (mid->driver_data == adm1272 || mid->driver_data == adm1278 ||
+	    mid->driver_data == adm1293 || mid->driver_data == adm1294)
+		config_read_fn = i2c_smbus_read_word_data;
+	else
+		config_read_fn = i2c_smbus_read_byte_data;
+	config = config_read_fn(client, ADM1275_PMON_CONFIG);
 	if (config < 0)
 		return config;
 
-	device_config = i2c_smbus_read_byte_data(client, ADM1275_DEVICE_CONFIG);
+	device_config = config_read_fn(client, ADM1275_DEVICE_CONFIG);
 	if (device_config < 0)
 		return device_config;
 
-- 
2.27.0.383.g050319c2ae-goog