On 3/30/23 15:36, Daniel Lezcano wrote:
On 30/03/2023 12:06, Mikko Perttunen wrote:
On 3/30/23 13:03, Daniel Lezcano wrote:
On 30/03/2023 11:49, Mikko Perttunen wrote:
From: Mikko Perttunen <mperttunen@xxxxxxxxxx>
Thermal zones located in power domains may not be accessible when
the domain is powergated. In this situation, reading the temperature
will return -BPMP_EFAULT. When evaluating trips, BPMP will internally
use -256C as the temperature for offline zones.
For smooth operation, for offline zones, return -EAGAIN when reading
the temperature and allow registration of zones even if they are
offline during probe.
I think it makes more sense to check if the power domain associated
with the device is powered up and if not return -EPROBE_DEFER.
The power domains in question are related to computer vision engines
that only get powered on when in use, possibly never if the user
doesn't run a computer vision workload on the system. We still want
other thermal zones to be available.
Ok, I see the point.
I'm worried about the semantic of the errors returned, the translation
from BPMP_EFAULT to EAGAIN and the assumption it is a disabled (may be
forever) thermal zone.
What does the documentation say for the error msg.rx.ret == -BPMP_EFAULT?
The documentation says
Value | Description
-------------- | -----------------------------------------
0 | Temperature query succeeded.
-#BPMP_EINVAL | Invalid request parameters.
-#BPMP_ENOENT | No driver registered for thermal zone.
-#BPMP_EFAULT | Problem reading temperature measurement.
In practice, what BPMP_EFAULT means here is that the hardware has no
indicated temperature for the zone, which really only happens if the
power domain is powered off.
Mikko
Signed-off-by: Mikko Perttunen <mperttunen@xxxxxxxxxx>
---
v2:
* Adjusted commit message.
* Patch 2/2 dropped for now since it is more controversial,
and this patch is more critical.
drivers/thermal/tegra/tegra-bpmp-thermal.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/thermal/tegra/tegra-bpmp-thermal.c
b/drivers/thermal/tegra/tegra-bpmp-thermal.c
index f5fd4018f72f..4ffc3bb3bf35 100644
--- a/drivers/thermal/tegra/tegra-bpmp-thermal.c
+++ b/drivers/thermal/tegra/tegra-bpmp-thermal.c
@@ -52,6 +52,8 @@ static int __tegra_bpmp_thermal_get_temp(struct
tegra_bpmp_thermal_zone *zone,
err = tegra_bpmp_transfer(zone->tegra->bpmp, &msg);
if (err)
return err;
+ if (msg.rx.ret == -BPMP_EFAULT)
+ return -EAGAIN;
if (msg.rx.ret)
return -EINVAL;
@@ -259,7 +261,12 @@ static int tegra_bpmp_thermal_probe(struct
platform_device *pdev)
zone->tegra = tegra;
err = __tegra_bpmp_thermal_get_temp(zone, &temp);
- if (err < 0) {
+
+ /*
+ * Sensors in powergated domains may temporarily fail to be
read
+ * (-EAGAIN), but will become accessible when the domain is
powered on.
+ */
+ if (err < 0 && err != -EAGAIN) {
devm_kfree(&pdev->dev, zone);
continue;
}
