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Date: Mon, 17 May 2021 08:51:23 -0700
From: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>,
Len Brown <lenb@...nel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH] ACPI: DPTF: Add new PCH FIVR methods
On Mon, 2021-05-17 at 17:20 +0200, Rafael J. Wysocki wrote:
> On Mon, May 17, 2021 at 7:54 AM Srinivas Pandruvada
> <srinivas.pandruvada@...ux.intel.com> wrote:
> >
> > Some additional information is required for updating PCH FIVR
> > values
> > upon WiFi channel changes.
> >
> > New attributes added to the existing sysfs:
> > fivr_switching_freq_mhz : Get the FIVR switching control frequency.
> > Uses ACPI method GFCS
> > fivr_switching_fault_status: Read the FIVR switching frequency
> > control
> > fault status. Uses ACPI method GFFS
> >
> > ssc_clock_info : Presents SSC (spread spectrum clock) information
> > for EMI
> > (Electro magnetic interference) control. Use ACPI method GEMI.
> > Refer
> > to the description of GEMI method below.
> >
> > GFFS
> > This ACPI method is used to read the FIVR switching frequency
> > control
> > fault status.
> > Bits Description
> > [0:0] Fault status when set to 1
> > [31:1] Reserved
> >
> > GFCS
> > This ACPI method is used to read the FIVR switching control
> > frequency.
> > Bits Description
> > [11:0] Actual Frequency = value * XTAL_FREQ / 128
>
> I was about to apply this, but one question.
>
> AFAICS the "show" function will simply evaluate GFCS and preset the
> returned value to the reader of the attribute, but the documentation
> says that this is the switching control frequency in MHz which
> doesn't
> seem to be consistent with the above information.
>
> Is the reader of the attribute required to know the XTAL frequency
> and
> apply the above formula to the value read from it? If so, the
> documentation should be clear about this.
>
Since XTAL_FREQ can be different on designs, user of the interface is
supposed to know that.
I will update the documentation and resend.
Thanks,
Srinivas
> > [31:12] Reserved
> >
> > GEMI
> > This ACPI method is used to read the programmed register value for
> > EMI
> > (Electro magnetic interference) control.
> >
> > Bits Description
> > [7:0] Sets clock spectrum spread percentage:
> > 0x00=0.2% , 0x3F=10%
> > 1 LSB = 0.1% increase in spread (for
> > settings 0x01 thru 0x1C)
> > 1 LSB = 0.2% increase in spread (for
> > settings 0x1E thru 0x3F)
> > [8] When set to 1, enables spread
> > spectrum clock
> > [9] 0: Triangle mode. FFC frequency
> > walks around the Fcenter in a linear
> > fashion
> > 1: Random walk mode. FFC frequency
> > changes randomly within the SSC
> > (Spread spectrum clock) range
> > [10] 0: No white noise. 1: Add white noise
> > to spread waveform
> > [11] When 1, future writes are ignored.
> >
> > Signed-off-by: Srinivas Pandruvada <
> > srinivas.pandruvada@...ux.intel.com>
> > ---
> > Documentation/ABI/testing/sysfs-platform-dptf | 40
> > +++++++++++++++++++
> > drivers/acpi/dptf/dptf_pch_fivr.c | 9 +++++
> > 2 files changed, 49 insertions(+)
> >
> > diff --git a/Documentation/ABI/testing/sysfs-platform-dptf
> > b/Documentation/ABI/testing/sysfs-platform-dptf
> > index 141834342a4d..f0c43711ad4f 100644
> > --- a/Documentation/ABI/testing/sysfs-platform-dptf
> > +++ b/Documentation/ABI/testing/sysfs-platform-dptf
> > @@ -111,3 +111,43 @@ Contact: linux-acpi@...r.kernel.org
> > Description:
> > (RW) The PCH FIVR (Fully Integrated Voltage
> > Regulator) switching frequency in MHz,
> > when FIVR clock is 38.4MHz.
> > +
> > +What:
> > /sys/bus/platform/devices/INTC1045:00/pch_fivr_switch_frequency/fiv
> > r_switching_freq_mhz
> > +Date: June, 2021
> > +KernelVersion: v5.14
> > +Contact: linux-acpi@...r.kernel.org
> > +Description:
> > + (RO) Get the FIVR switching control frequency in
> > MHz.
> > +
> > +What:
> > /sys/bus/platform/devices/INTC1045:00/pch_fivr_switch_frequency/fiv
> > r_switching_fault_status
> > +Date: June, 2021
> > +KernelVersion: v5.14
> > +Contact: linux-acpi@...r.kernel.org
> > +Description:
> > + (RO) Read the FIVR switching frequency control
> > fault status.
> > +
> > +What:
> > /sys/bus/platform/devices/INTC1045:00/pch_fivr_switch_frequency/ssc
> > _clock_info
> > +Date: June, 2021
> > +KernelVersion: v5.14
> > +Contact: linux-acpi@...r.kernel.org
> > +Description:
> > + (RO) Presents SSC (spread spectrum clock)
> > information for EMI
> > + (Electro magnetic interference) control. This is a
> > bit mask.
> > + Bits Description
> > + [7:0] Sets clock spectrum spread percentage:
> > + 0x00=0.2% , 0x3F=10%
> > + 1 LSB = 0.1% increase in spread (for
> > + settings 0x01 thru 0x1C)
> > + 1 LSB = 0.2% increase in spread (for
> > + settings 0x1E thru 0x3F)
> > + [8] When set to 1, enables spread
> > + spectrum clock
> > + [9] 0: Triangle mode. FFC frequency
> > + walks around the Fcenter in a linear
> > + fashion
> > + 1: Random walk mode. FFC frequency
> > + changes randomly within the SSC
> > + (Spread spectrum clock) range
> > + [10] 0: No white noise. 1: Add white noise
> > + to spread waveform
> > + [11] When 1, future writes are ignored.
> > diff --git a/drivers/acpi/dptf/dptf_pch_fivr.c
> > b/drivers/acpi/dptf/dptf_pch_fivr.c
> > index 5fca18296bf6..22c4ae0401ef 100644
> > --- a/drivers/acpi/dptf/dptf_pch_fivr.c
> > +++ b/drivers/acpi/dptf/dptf_pch_fivr.c
> > @@ -55,15 +55,24 @@ static ssize_t name##_store(struct device
> > *dev,\
> >
> > PCH_FIVR_SHOW(freq_mhz_low_clock, GFC0)
> > PCH_FIVR_SHOW(freq_mhz_high_clock, GFC1)
> > +PCH_FIVR_SHOW(ssc_clock_info, GEMI)
> > +PCH_FIVR_SHOW(fivr_switching_freq_mhz, GFCS)
> > +PCH_FIVR_SHOW(fivr_switching_fault_status, GFFS)
> > PCH_FIVR_STORE(freq_mhz_low_clock, RFC0)
> > PCH_FIVR_STORE(freq_mhz_high_clock, RFC1)
> >
> > static DEVICE_ATTR_RW(freq_mhz_low_clock);
> > static DEVICE_ATTR_RW(freq_mhz_high_clock);
> > +static DEVICE_ATTR_RO(ssc_clock_info);
> > +static DEVICE_ATTR_RO(fivr_switching_freq_mhz);
> > +static DEVICE_ATTR_RO(fivr_switching_fault_status);
> >
> > static struct attribute *fivr_attrs[] = {
> > &dev_attr_freq_mhz_low_clock.attr,
> > &dev_attr_freq_mhz_high_clock.attr,
> > + &dev_attr_ssc_clock_info.attr,
> > + &dev_attr_fivr_switching_freq_mhz.attr,
> > + &dev_attr_fivr_switching_fault_status.attr,
> > NULL
> > };
> >
> > --
> > 2.27.0
> >
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