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@xxxxxxxxx>
> >
> > 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@xxxxxxxxx>
> > [Upstream from SONiC https://github.com/Azure/sonic-linux-kernel/pull/215]
> > Signed-off-by: Paul Menzel <pmenzel@xxxxxxxxxxxxx>
> > ---
> >   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