Negative value returns for sensor in tiogapass

[Ed Tanous]

On Fri, Feb 26, 2021 at 12:55 AM Jayashree D <jayashree-d at hcl.com> wrote:
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> Classification: Public
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> Hi Team,
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> Recently, I have tested sensors for tiogapass, in which one sensor returns negative value.
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> After analysing the code in the dbus-sensors repo, I found the following issue.
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> dbus-sensors/IpmbSensor.cpp at master · openbmc/dbus-sensors (github.com)
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> From the above link, We need only below line in the code to process the HSC sensors value for tiogapass.
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> int16_t value = ((data[4] << 8) | data[3]);
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> Since the below logic is added, the values get shifted and getting negative values as output.
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> constexpr const size_t shift = 16 - 11; // 11bit into 16bit
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> value <<= shift;
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> value >>= shift;
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> Could you please suggest any idea to resolve this issue.

I haven't looked at this in detail, but we should follow whatever the
spec says here.  If whomever wrote this originally put in the wrong
math (which seems likely, given they were implementing 4 types and
probably only using one) then we should just get it fixed and do what
the spec says.

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> Regards,
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> Jayashree
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