Hi Khali,
On Mon, 9 May 2005 15:35:36 +0200 (CEST), "Jean Delvare" <khali at linux-fr.org> wrote:
>> but if driver scaling has been vetoed, I'd rather know now than
>> submit something unwanted. lm87 driver almost has it, carrying
>> scaling factors in private memory, loaded at chip detect time.
>
>The rule is: drivers should provide the voltages as seen at their pins.
Yes, so the Winbond drivers (at least w82627hf) do not report pin
voltage for 5V and 5VSB thus need this or similar fix.
>This means that, where scaling is external, it has to be done in
>user-space, while where scaling is internal, it has to be done by the
>driver itself. All drivers respect that rule as far as I remember.
Except the exceptions :)
>> * These sensor chips perform internal scaling for 5V (in3) and 5VSB
>
>I don't think so. Can you point us to a datasheet stating this?
Any Winbond datasheet :)
W83L784R 6.3.1:
"The first function is to supply internal analog power in the W83L784R
and the second function is that this voltage with 5V is connected to
internal serial resistors to monitor the +5V voltage. The value of
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
two serial resistors are 34K ohms and 50K ohms so that input voltage
^^^^^^^^^^^^^^^^^^^^^
to ADC is 2.98V which is less than 4.096V of ADC maximum input voltage."
W83627HF:
"The first function is to supply internal analog power in the W83627HF
and the second function is that this voltage with 5V is connected to
internal serial resistors to monitor the +5V voltage. The value of two
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
serial resistors are 34K ohms and 50K ohms so that input voltage to ADC
^^^^^^^^^^^^^^^^^^^^^
is 2.98V which is less than 4.096V of ADC maximum input voltage.
The Pin 61 is connected to 5VSB voltage. W83627HF monitors this voltage
and the internal two serial resistors are 17K W and 33K W so that input
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^-- W is ohm symbol
voltage to ADC is 3.3V which less than 4.096V of ADC maximum input voltage."
W83627THF Section 7.3.1 pin 114, pin 61 34k, 51k
Need I go on? I surveyed every datasheet I could find (w83697hf circuit
overlay problem been fixed too).
>
>> Comments?
>
>Your code makes sense for external resistors, but not for internal
>scaling as far as I can see, so it won't be of any help in the drivers.
Okay another exception for Winbond chips. But this method can go
either place, driver or user-space, I'm trying to demonstrate a
different way of doing scaling that suits end-user calibration, as
well as point out where drivers differ from sysfs standard usage.
>And libsensors mostly works the way you describe already, just not in as
>formal a way (because compute lines were meant for all values, not just
>voltages).
libsensors compute lines suit most situations, I hit one where it
fails, plus the silliness (IMHO) of entering every formula twice,
parameter based scaling avoids that, what I'm discussing here is
something for voltages, that seems to work very well. Whether it
gets into sensors as an alternate compute method, or is a utility
that produces 'normalised' compute terms doesn't really matter in
long run.
The benefit of doing resistor based scaling is that resistor value
are in a discrete value series so one may pick an unambiguous pair
for a particular positive or negative voltage reading. A user-space
program can take observed reading (BIOS or measured) and produce
'best match' pair that works, as mobo maker using same discrete
value series.
You did ask me once how to do scaling without reciprocal formula
entry? This is one way how. It doesn't have to go into driver,
though perhaps partially, to meet self-scaled input requirements.
>So all in all I think that you are trying to fix a problem that doesn't
>exist in the first place, sorry.
Disagree :o) The story:
I started on this originally because I could find no documentation on
which adm9240 VccpX input was monitoring respective -5 and -12 volt
inputs on Intel SE440BX-2 mobo -- what surprised me back then was the
totally unambiguous answer the method of using resistor series values
gave. Not only told me resistor values, it unambiguously told me which
sensor input was measuring which negative voltage. I think I posted
that here a while ago.
libsensors cannot compute negative voltages for adm9240 as they require
two inputs for the calculation? You not corrected that notion for me,
did I miss some thing in compute syntax or it simply isn't there?
ADM9240 has no reference to drive top of resistor divider, so one must
measure 5V and VccpX in order to discover negative reading.
There are notes in archives about adm9240 having problems displaying
correct voltages, if they mean negative voltages I have the answer,
further, as it compares observed vs measured value it accounts for
input pin loading (~140k).
Parameter based conversion fixes the compute lines for voltages by
relating them to 'real world' values that can be inferred, you might
consider that idea for libsensors, I get terribly confused by the
number of exceptions to the 'rules' for drivers :)
An alternative is to simply provide a script that does the resistor
ratio stuff then 'normalise' the result so it can be plugged into
sensors. Least disturbance of the system? Plus the ability to tell
which input is monitoring what voltage -- maybe I was lucky with Intel,
they used E12 (10%) series, E24 (5%) series works well, my studies
indicate E24 series would be close enough, given the relatively poor
resolution and accuracy of the sensor chip measurements.
Trialling with E96 (1%) series is too noisy on 12V measurement due
to poor measurement resolution, and it was a single bit (16mV) doing
the damage -- when it was 'right' datasheet value came up (56/232),
one bit higher and a different offering.
I'm still exploring the hwmon system, finding a balance between what
can be done versus what should be done in drivers, I now see we don't
really want a lot of extra accessors populating sysfs if that is so
expensive. I did go back to the Jan2003 sysfs discussions, so I'm
dragging up stuff that you have already settled. This is still new
area for me.
Sensors needs a cleanup, and it seems right at the core parser, that's
not a nice one to take on, but from end-user point of view it needs
doing. One day :) The lex/yacc parser in sensors is not terribly
bright, I've forgotten if there is more modern way to build a parser,
but the core parser doesn't look right, although its been a few years
since I did one ('97 or '98), I'd have to dig it up and look.
The techniques, ideas I'm exploring don't _have_ to go into the
drivers, I'm running them either way, direct sysfs access with shell
script (see below) or in driver, that is not an issue for me. Though
I had to ask when I see it so close to being done in driver, but then
complicated by the restrictions placed on sysfs data transfer and
naming.
Okay, I'm dancing all over the drivers at the moment, trying to discover
boundaries, as many are not documented.
Once I have an idea of boundaries, document that, look at what is left
for user-space. At times I'm being too picky as measurement and control
design is what I did for a living a long time ago. Other times I can't
see wood for trees. (older I get, better I was :)
Example with: Linux 2.6.12-rc3-mm3b. (First time I been game to boot -mm)
root at sempro:~# lsmod
Module Size Used by
w83627hf 29480 0
i2c_sensor 2944 1 w83627hf <<== unmodified
i2c_isa 1856 0
via_agp 7744 1
agpgart 29256 1 via_agp
Grant's voltage divider value finder,
R1 is from E24 (5%) series, R2 from E24 series
Working on: 12V
~~~~~~~~~~~~~~~~~~
R1 R2 Error Series
---- ----- ------ ---
2000 5600 0.088% E24 <<== match datasheet 10/28 (28 is from E96)
4300 12000 0.249% E24
Working on: -12V
~~~~~~~~~~~~~~~~~~
R1 R2 Error Series
---- ----- ------ ---
2400 10000 0.030% E24 <<== closet to datasheet 56/232 = 0.241
1800 7500 0.040% E24
3600 15000 0.107% E24
4300 18000 0.423% E24
Working on: -5V
~~~~~~~~~~~~~~~~~~
R1 R2 Error Series
---- ----- ------ ---
5600 12000 0.074% E24 <<== matches datasheet suggested values
2200 4700 0.212% E24
2000 4300 0.490% E24
x raw BIOS final label R1 R2
0 1552 1550 1552 Vcore 0 0
2 3296 3290 3296 3.3 0 0
3 3040 5130 5107 5 50 34 <<== 50/34 are internal to sensor chip
4 3152 11970 11977 12 20 56
5 624 -11780 -11705 -12 56 232
6 848 -5040 -5049 -5 56 120
7 3280 5070 4969 5VSB 33 17 <<== 33/17 also internal resistors
8 3376 3370 3376 Vbatt 0 0
raw is what sysfs gives, BIOS are observed readings, final are readings
as per label column with R1, R2 as per:
# -------o--> +5V, +5VSB, +12V Measuring positive V > 4V
# | Vplus
# -
# | | R2 ---------------------- Measuring negative V
# | | | | ____ ____
# - | 3600mV Vref |--|____|--o--|____|--->
# | Vin | | R1 | R2
# o-----------| 0..4096mV | | -5V, -12V
# | | 0..4096mV |---------- Vminus
# - | W83697HF | Vin
# | | R1 | |
# | | ----------------------
# -
# |
# -------o--> 0V
Data structure is simple (for w83697hf):
Vlabel=("Vcore" "-" " 3.3" " 5" " 12" " -12" " -5" " 5VSB" "Vbatt")
# +5 +12 -12 -5 5VSB
Vsfind=(0 0 0 0 1 2 2 0 0) # 0 builtin, 1 = pos, 2 = neg
Vscale=(0 0 0 1 1 2 2 1 0) # 0 noscale, 1 = pos, 2 = neg
R1spec=(0 0 0 50 20 56 56 33 0) # known and datasheet values
R2spec=(0 0 0 34 56 232 120 17 0)
Vbios=(1550 0 3290 5130 11970 -11780 -5040 5070 3370) # mV reported by BIOS
Summary
````````
I've described a parameter based voltage reporting system that suits
some chips that describe their scaling in terms of resistor values,
a method for calibrating sensor readings to match observed BIOS or
measured readings. The result of this can be 'normalised' to suit
current libsensors 'compute' lines or placed in drivers where needed.
A mobo manufacturer is likely to use less expensive E12 or E24 series
resistor values for external voltage scaling. My 2 of 2 mobo survey
confirms this. One mobo left to try is a the Gigglebyte shambles that
does not follow manuf. guidelines (it87).
As far as drivers go, the winbond series drivers need fixing to report
internally scaled voltages, winbond have two standards: an earlier
5V -> 34/50, 5VSB -> 17/33 (where present), and a later standard where
both 5V and 5VSB are 34/51.
Query
``````
The query I have is how to tell libsensors to produce a negative voltage
readings for adm9240, as each depends on two input channel values.
--Grant.
