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List:       linuxbios
Subject:    [coreboot] Re: Intel sVID controller and SVID bus.
From:       Alex Feinman <alexfeinman () hotmail ! com>
Date:       2019-02-22 22:43:38
Message-ID: BYAPR15MB34453BF8D5BB1CD5D285B2ABB97F0 () BYAPR15MB3445 ! namprd15 ! prod ! outlook ! com
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Intel CPUs typically drive SVID-enabled PMICs using an internal small core =
(at least Core m and Core i parts). In any case, the peripherals on SVID bu=
s have addresses that sometimes are assigned via bootstrap pins. Your Denve=
rton design probably has a TI and ST Micro PMICs connected to SVID. If the =
device does not respond on the expected address, the CPU probably won't ret=
ry communication. I'm not closely familiar with Atom family, so I don't kno=
w what it would do. The Core CPU will raise CATERR signal and die. In any c=
ase, I recommend trying to capture what happens on the SVID bus from the ve=
ry moment of powerup. Expect a low-voltage (~ 1V) 25 MHz I2C-like signal.

If you do capture it and you have a support agreement with Intel, you can a=
sk them for an SVID decoder. You might also try decoding it manually (searc=
h web for "vr pwm specification intel"), using the Intel spec.

Finally, if you determine that the peripherals in your system indeed nak th=
e SVID traffic, the actual addresses of these peripherals can be programmed=
 in the BIOS code, however I am not certain if this is something happening =
inside the FSP and if it can be modified externally.



From: dponamorev@gmail.com <dponamorev@gmail.com>
Sent: Friday, February 22, 2019 7:05 AM
To: coreboot@coreboot.org
Subject: [coreboot] Intel sVID controller and SVID bus.
=A0
On the motherboard developed by our company (intel atom denverton 3538), th=
ere is a low performance of the processor and memory. When trying to monito=
r the exchange of the SVID bus lines with the oscilloscope (SVID_CLK, SVID_=
DATA and SVID_ALERT), no activity was noticed. Circuit design is correct (p=
assed Intel review).
Could this be the reason for the slow speed of the processor and memory? Do=
 I need to activate this technology in coreboot or FSP? Is there any way to=
 check the operation of the sVID controller from Linux?
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