linux-kernel - Re: [PATCH 5/6] platform/x86: ISST: Process read/write blocked feature status

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Message-ID: <0c2b6e18a95d92a1a8a8ce4f8a110f23391f42ee.camel@linux.intel.com>
Date:   Thu, 30 Nov 2023 09:30:50 -0500
From:   srinivas pandruvada <srinivas.pandruvada@...ux.intel.com>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc:     Hans de Goede <hdegoede@...hat.com>, markgross@...nel.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        platform-driver-x86@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/6] platform/x86: ISST: Process read/write blocked
 feature status

On Thu, 2023-11-30 at 14:20 +0200, Ilpo Järvinen wrote:
> On Tue, 28 Nov 2023, Srinivas Pandruvada wrote:
> 
> > When a feature is read blocked, don't continue to read SST
> > information
> > and register with SST core.
> > 
> > When the feature is write blocked, continue to offer read interface
> > for
> > SST parameters, but don't allow any operation to change state. A
> > state
> > change results from SST level change, feature change or class of
> > service
> > change.
> > 
> > Signed-off-by: Srinivas Pandruvada
> > <srinivas.pandruvada@...ux.intel.com>
> > ---
> >  .../intel/speed_select_if/isst_tpmi_core.c    | 25
> > +++++++++++++++++++
> >  1 file changed, 25 insertions(+)
> > 
> > diff --git
> > a/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> > b/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> > index 0b6d2c864437..ed3a04d6c99c 100644
> > --- a/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> > +++ b/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> > @@ -514,6 +516,9 @@ static long isst_if_clos_param(void __user
> > *argp)
> >         if (!power_domain_info)
> >                 return -EINVAL;
> >  
> > +       if (power_domain_info->write_blocked)
> > +               return -EPERM;
> > +
> 
> I don't understand this, doesn't this now -EPERM both
> _write_cp_info() AND
> _read_cp_info()??? Does _read_cp_info() also change state??
You have a point here. Unlike other SST features, CP access is useful
for OS as it know workloads and priorities.
But I will change for consistency.

Thanks,
Srinivas

> 
> >         if (clos_param.get_set) {
> >                 _write_cp_info("clos.min_freq",
> > clos_param.min_freq_mhz,
> >                                (SST_CLOS_CONFIG_0_OFFSET +
> > clos_param.clos * SST_REG_SIZE),
> > @@ -602,6 +607,9 @@ static long isst_if_clos_assoc(void __user
> > *argp)
> >  
> >                 power_domain_info = &sst_inst-
> > >power_domain_info[punit_id];
> >  
> > +               if (power_domain_info->write_blocked)
> > +                       return -EPERM;
> 
> Same here, this blocks also the get path?
> 
>