[PATCH] thermal/drivers/mediatek/lvts_thermal: Make readings valid in filtered mode

[Chen-Yu Tsai]

On Thu, Jul 06, 2023 at 12:14:33PM -0400, Nícolas F. R. A. Prado wrote:
> Currently, when a controller is configured to use filtered mode, thermal
> readings are valid only about 30% of the time.
> 
> Upon testing, it was noticed that lowering any of the interval settings
> resulted in an improved rate of valid data. The same was observed when
> decreasing the number of samples for each sensor (which also results in
> quicker measurements).
> 
> Retrying the read with a timeout longer than the time it takes to
> resample (about 344us with these settings and 4 sensors) also improves
> the rate.
> 
> Lower all timing settings to the minimum, configure the filtering to
> single sample, and poll the measurement register for at least one period
> to improve the data validity on filtered mode.  With these changes in
> place, out of 100000 reads, a single one failed, ie 99.999% of the data
> was valid.
> 
> Signed-off-by: Nícolas F. R. A. Prado <nfraprado at collabora.com>

Reviewed-by: Chen-Yu Tsai <wenst at chromium.org>
Tested-by: Chen-Yu Tsai <wenst at chromium.org>

on Hayato. Reading out the temperature is now quite reliable.

> 
> ---
> 
>  drivers/thermal/mediatek/lvts_thermal.c | 15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/thermal/mediatek/lvts_thermal.c b/drivers/thermal/mediatek/lvts_thermal.c
> index 1e11defe4f35..b5fb1d8bc3d8 100644
> --- a/drivers/thermal/mediatek/lvts_thermal.c
> +++ b/drivers/thermal/mediatek/lvts_thermal.c
> @@ -58,11 +58,11 @@
>  #define LVTS_PROTTC(__base)		(__base + 0x00CC)
>  #define LVTS_CLKEN(__base)		(__base + 0x00E4)
>  
> -#define LVTS_PERIOD_UNIT			((118 * 1000) / (256 * 38))
> -#define LVTS_GROUP_INTERVAL			1
> -#define LVTS_FILTER_INTERVAL		1
> -#define LVTS_SENSOR_INTERVAL		1
> -#define LVTS_HW_FILTER				0x2
> +#define LVTS_PERIOD_UNIT			0
> +#define LVTS_GROUP_INTERVAL			0
> +#define LVTS_FILTER_INTERVAL		0
> +#define LVTS_SENSOR_INTERVAL		0
> +#define LVTS_HW_FILTER				0x0

This hunk conflicts with

    thermal/drivers/mediatek/lvts_thermal: Disable undesired interrupts

from your other series

>  #define LVTS_TSSEL_CONF				0x13121110
>  #define LVTS_CALSCALE_CONF			0x300
>  #define LVTS_MONINT_CONF			0x9FBF7BDE

on this line.

> @@ -257,6 +257,7 @@ static int lvts_get_temp(struct thermal_zone_device *tz, int *temp)
>  	struct lvts_sensor *lvts_sensor = thermal_zone_device_priv(tz);
>  	void __iomem *msr = lvts_sensor->msr;
>  	u32 value;
> +	int rc;
>  
>  	/*
>  	 * Measurement registers:
> @@ -269,7 +270,7 @@ static int lvts_get_temp(struct thermal_zone_device *tz, int *temp)
>  	 * 16	: Valid temperature
>  	 * 15-0	: Raw temperature
>  	 */
> -	value = readl(msr);
> +	rc = readl_poll_timeout(msr, value, value & BIT(16), 240, 400);
>  
>  	/*
>  	 * As the thermal zone temperature will read before the
> @@ -282,7 +283,7 @@ static int lvts_get_temp(struct thermal_zone_device *tz, int *temp)
>  	 * functionning temperature and directly jump to a system
>  	 * shutdown.
>  	 */
> -	if (!(value & BIT(16)))
> +	if (rc)
>  		return -EAGAIN;
>  
>  	*temp = lvts_raw_to_temp(value & 0xFFFF);
> -- 
> 2.41.0
>