[PATCH] hwmon: (pmbus_core) Check adapter PEC support

[PATCH] hwmon: (pmbus_core) Check adapter PEC support

[Paul Menzel]

From: Madhava Reddy Siddareddygari <msiddare@cisco.com>

Currently, for Packet Error Checking (PEC) only the controller
is checked for support. This causes problems on the cisco-8000
platform where a SMBUS transaction errors are observed. This is
because PEC has to be enabled only if both controller and
adapter support it.

Added code to check PEC capability for adapter and enable it
only if both controller and adapter supports PEC.

Signed-off-by: Madhava Reddy Siddareddygari <msiddare@cisco.com>
[Upstream from SONiC https://github.com/Azure/sonic-linux-kernel/pull/215]
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
---
 drivers/hwmon/pmbus/pmbus_core.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
index bbd745178147..7fbd82b7560d 100644
--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c
@@ -2214,11 +2214,13 @@ static int pmbus_init_common(struct i2c_client *client, struct pmbus_data *data,
 		data->has_status_word = true;
 	}
 
-	/* Enable PEC if the controller supports it */
-	if (!(data->flags & PMBUS_NO_CAPABILITY)) {
-		ret = i2c_smbus_read_byte_data(client, PMBUS_CAPABILITY);
-		if (ret >= 0 && (ret & PB_CAPABILITY_ERROR_CHECK))
+	/* Enable PEC if the controller and bus supports it */
+	ret = i2c_smbus_read_byte_data(client, PMBUS_CAPABILITY);
+	if (ret >= 0 && (ret & PB_CAPABILITY_ERROR_CHECK)) {
+		if (i2c_check_functionality(client->adapter,
+			I2C_FUNC_SMBUS_PEC)) {
 			client->flags |= I2C_CLIENT_PEC;
+		}
 	}
 
 	/*
-- 
2.32.0.rc2

Re: [PATCH] hwmon: (pmbus_core) Check adapter PEC support

[Guenter Roeck]

On Fri, Jun 04, 2021 at 03:57:14PM +0200, Paul Menzel wrote:
> From: Madhava Reddy Siddareddygari <msiddare@cisco.com>
> 
> Currently, for Packet Error Checking (PEC) only the controller
> is checked for support. This causes problems on the cisco-8000
> platform where a SMBUS transaction errors are observed. This is
> because PEC has to be enabled only if both controller and
> adapter support it.
> 
> Added code to check PEC capability for adapter and enable it
> only if both controller and adapter supports PEC.
> 
> Signed-off-by: Madhava Reddy Siddareddygari <msiddare@cisco.com>
> [Upstream from SONiC https://github.com/Azure/sonic-linux-kernel/pull/215]
> Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
> ---
>  drivers/hwmon/pmbus/pmbus_core.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
> index bbd745178147..7fbd82b7560d 100644
> --- a/drivers/hwmon/pmbus/pmbus_core.c
> +++ b/drivers/hwmon/pmbus/pmbus_core.c
> @@ -2214,11 +2214,13 @@ static int pmbus_init_common(struct i2c_client *client, struct pmbus_data *data,
>  		data->has_status_word = true;
>  	}
>  
> -	/* Enable PEC if the controller supports it */
> -	if (!(data->flags & PMBUS_NO_CAPABILITY)) {

What is the rationale for removing this check ?
AFAICS that will render the ibm-cffps driver unusable.

Guenter

> -		ret = i2c_smbus_read_byte_data(client, PMBUS_CAPABILITY);
> -		if (ret >= 0 && (ret & PB_CAPABILITY_ERROR_CHECK))
> +	/* Enable PEC if the controller and bus supports it */
> +	ret = i2c_smbus_read_byte_data(client, PMBUS_CAPABILITY);
> +	if (ret >= 0 && (ret & PB_CAPABILITY_ERROR_CHECK)) {
> +		if (i2c_check_functionality(client->adapter,
> +			I2C_FUNC_SMBUS_PEC)) {
>  			client->flags |= I2C_CLIENT_PEC;
> +		}
>  	}
>  
>  	/*
> -- 
> 2.32.0.rc2
> 

Re: [PATCH] hwmon: (pmbus_core) Check adapter PEC support

[Paul Menzel]

Dear Guenter,


Am 05.06.21 um 02:51 schrieb Guenter Roeck:
> On Fri, Jun 04, 2021 at 03:57:14PM +0200, Paul Menzel wrote:
>> From: Madhava Reddy Siddareddygari <msiddare@cisco.com>
>>
>> Currently, for Packet Error Checking (PEC) only the controller
>> is checked for support. This causes problems on the cisco-8000
>> platform where a SMBUS transaction errors are observed. This is
>> because PEC has to be enabled only if both controller and
>> adapter support it.
>>
>> Added code to check PEC capability for adapter and enable it
>> only if both controller and adapter supports PEC.
>>
>> Signed-off-by: Madhava Reddy Siddareddygari <msiddare@cisco.com>
>> [Upstream from SONiC https://github.com/Azure/sonic-linux-kernel/pull/215]
>> Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
>> ---
>>   drivers/hwmon/pmbus/pmbus_core.c | 10 ++++++----
>>   1 file changed, 6 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
>> index bbd745178147..7fbd82b7560d 100644
>> --- a/drivers/hwmon/pmbus/pmbus_core.c
>> +++ b/drivers/hwmon/pmbus/pmbus_core.c
>> @@ -2214,11 +2214,13 @@ static int pmbus_init_common(struct i2c_client *client, struct pmbus_data *data,
>>   		data->has_status_word = true;
>>   	}
>>   
>> -	/* Enable PEC if the controller supports it */
>> -	if (!(data->flags & PMBUS_NO_CAPABILITY)) {
> 
> What is the rationale for removing this check ?
> AFAICS that will render the ibm-cffps driver unusable.

I screwed up forward porting this change. Thank you for spotting this. I 
sent a second iteration/version 2 of this patch.


Kind regards,

Paul


>> -		ret = i2c_smbus_read_byte_data(client, PMBUS_CAPABILITY);
>> -		if (ret >= 0 && (ret & PB_CAPABILITY_ERROR_CHECK))
>> +	/* Enable PEC if the controller and bus supports it */
>> +	ret = i2c_smbus_read_byte_data(client, PMBUS_CAPABILITY);
>> +	if (ret >= 0 && (ret & PB_CAPABILITY_ERROR_CHECK)) {
>> +		if (i2c_check_functionality(client->adapter,
>> +			I2C_FUNC_SMBUS_PEC)) {
>>   			client->flags |= I2C_CLIENT_PEC;
>> +		}
>>   	}
>>   
>>   	/*
>> -- 
>> 2.32.0.rc2