Many of the Rockchip SoCs support storing trim values for the sensors in
factory programmable memory. These values specify a fixed offset from
the sensor's returned temperature to get a more accurate picture of what
temperature the silicon is actually at.

The way this is implemented is with various OTP cells, which may be
absent. There may both be whole-TSADC trim values, as well as per-sensor
trim values.

In the downstream driver, whole-chip trim values override the per-sensor
trim values. This rewrite of the functionality changes the semantics to
something I see as slightly more useful: allow the whole-chip trim
values to serve as a fallback for lacking per-sensor trim values,
instead of overriding already present sensor trim values.

Additionally, the chip may specify an offset (trim_base, trim_base_frac)
in degrees celsius and degrees decicelsius respectively which defines
what the basis is from which the trim, if any, should be calculated
from. By default, this is 30 degrees Celsius, but the chip can once
again specify a different value through OTP cells.

The implementation of these trim calculations have been tested
extensively on an RK3576, where it was confirmed to get rid of pesky 1.8
degree Celsius offsets between certain sensors.

Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>

Thanks to Heiko's work getting OTP working on the RK3576, we can specify
the thermal sensor trim values which are stored there now, and with my
driver addition to rockchip_thermal, we can make use of these.

Add them to the devicetree for the SoC.

Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>

Several Rockchip SoCs, such as the RK3576, can store calibration trim
data for thermal sensors in OTP cells. This capability should be
documented.

Such a rockchip thermal sensor may reference cell handles that store
both a chip-wide trim for all the sensors, as well as cell handles
for each individual sensor channel pointing to that specific sensor's
trim value.

Additionally, the thermal sensor may optionally reference cells which
store the base in terms of degrees celsius and decicelsius that the trim
is relative to.

Each SoC that implements this appears to have a slightly different
combination of chip-wide trim, base, base fractional part and
per-channel trim, so which ones do which is documented in the bindings.

Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>

Ye Zhang authored 2 months ago and Nicolas Frattaroli committed 1 month ago

The RK3576 SoC has six TS-ADC channels: TOP, BIG_CORE, LITTLE_CORE,
DDR, NPU and GPU.

Signed-off-by: Ye Zhang <ye.zhang@rock-chips.com>
[ported to mainline, reworded commit message]
Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>

Add the TSADC node to the RK3576. Additionally, add everything the TSADC
needs to function, i.e. thermal zones, their trip points and maps, as
well as adjust the CPU cooling-cells property.

The polling-delay properties are set to 0 as we do have interrupts for
this TSADC on this particular SoC.

Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>

Add a new compatible for the thermal sensor device on the RK3576 SoC.

Acked-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>

# Conflicts:
#	kernel/sysctl.c

# Conflicts:
#	kernel/rcu/tiny.c

# Conflicts:
#	drivers/scsi/scsi_debug.c