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

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Message-ID: <20200709140553.GA62629@roeck-us.net>
Date:   Thu, 9 Jul 2020 07:05:53 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Chu Lin <linchuyuan@...gle.com>
Cc:     belgaied@...gle.com, jasonling@...gle.com, jdelvare@...e.com,
        linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org,
        zhongqil@...gle.com
Subject: Re: [PATCH v2] hwmon: adm1275: Make sure we are reading enough data
 for different chips

On Thu, Jul 09, 2020 at 04:06:12AM +0000, Chu Lin wrote:
> 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>

Applied.

Thanks a lot for analyzing and fixing the problem.

Guenter

> ---
> 
> 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;
>