Re: [PATCH v3] thermal: qcom: tsens: atomic temperature read with hardware-guided retries

[Daniel Lezcano]

Hi Priyansh,

On 5/11/26 09:10, Priyansh Jain wrote:
> 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.

In future, please add the '---' annotation in order to have the 
changelog below not included when git-apply'ing the patch

> Changes in v2:
>
> - Reverted merging of the valid-bit and LAST_TEMP register field logic
>    to preserve the regmap differences between TSENS versions
> - Defined valid-bit support and last temperature resolution for all
>    TSENS v1 and v2 feature structures
> - Defined last temperature resolution for Tsens v0 feature structure
> - Dropped tsens version checks in favor of valid-bit capability
> - Computed masks from resolution to keep a single source of truth
> - Minor code cleanups based on review feedback
>
> Changes in v3:
> - Remove valid_bit, last_temp_mask, and last_temp_resolution fields from
>    struct tsens_features in tsens.h
> - Compute last_temp_mask, resolution, and valid_bit on-the-fly using
>    regmap field definitions
> - Remove field initializations from all platform data files
>    (tsens-v0_1.c, tsens-v1.c, tsens-v2.c)
> - Remove the initialization line in init_common() that was computing
>    last_temp_mask
>
> Signed-off-by: Priyansh Jain <priyansh.jain@xxxxxxxxxxxxxxxx>
> ---

Applied, thanks