Re: [PATCH v2 1/2] thermal: qcom: tsens: atomic temperature read with hardware-guided retries
From: Priyansh Jain
Date: Mon May 11 2026 - 02:16:20 EST
On 08-05-2026 05:39 pm, Konrad Dybcio wrote:
On 5/8/26 12:06 PM, Priyansh Jain wrote:Yes, that's correct. Thanks for pointing this out — I will update the code accordingly in the next patch version.
The existing TSENS temperature read logic polls the valid bit and then
reads the temperature register. When temperature reads are triggered
at very short intervals, this can race with hardware updates and allow
the temperature field to be read while it is still being updated.
In this case, the valid bit may already be asserted even though the
temperature value is transitioning, resulting in an incorrect reading.
Hardware programming guidelines require the temperature value and the
valid bit to be sampled atomically in the same read transaction. A
reading is considered valid only if the valid bit is observed set in
that same sample.
The guidelines further specify that software should attempt the
temperature read up to three times to account for transient update
windows. If none of the attempts observe a valid sample, a stable
fallback value must be returned: if the first and second samples match,
the second value is returned; otherwise, if the second and third
samples match, the third value is returned.
Update the TSENS sensor read logic to implement atomic sampling along
with the recommended retry-and-compare fallback behavior. This removes
the race window and ensures deterministic temperature values in
accordance with hardware requirements.
Signed-off-by: Priyansh Jain <priyansh.jain@xxxxxxxxxxxxxxxx>
---
[...]
struct tsens_features {
unsigned int ver_major;
@@ -522,6 +526,9 @@ struct tsens_features {
unsigned int max_sensors;
int trip_min_temp;
int trip_max_temp;
+ int valid_bit;
+ int last_temp_mask;
+ u32 last_temp_resolution;
You don't need this now that you aren't altering the regfield
definitions
Thanks,
Priyansh
Konrad