[PATCH] Input: touchscreen: tsc2007: Reduce I2C transactions for Z2 read

[PATCH] Input: touchscreen: tsc2007: Reduce I2C transactions for Z2 read

[Yuki Horii]

From: Yuki Horii <yuuki198708@gmail.com>

The current implementation sends a separate power-down command
after reading the Z2 value, resulting in an extra I2C
transaction per measurement cycle.

The TSC2007 command byte contains a 2-bit power-down mode
selection field. By selecting the power-down state in the Z2
measurement command, the device powers down after the Z2 A/D
conversion completes, eliminating the subsequent power-down
transaction.

This reduces the number of I2C transactions by one per touch
measurement cycle, decreasing I2C bus overhead and improving
touch sampling performance.

Signed-off-by: Yuki Horii <yuuki198708@gmail.com>
---
 drivers/input/touchscreen/tsc2007_core.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/input/touchscreen/tsc2007_core.c b/drivers/input/touchscreen/tsc2007_core.c
index 948935de894b..ff60245baa96 100644
--- a/drivers/input/touchscreen/tsc2007_core.c
+++ b/drivers/input/touchscreen/tsc2007_core.c
@@ -61,10 +61,8 @@ static void tsc2007_read_values(struct tsc2007 *tsc, struct ts_event *tc)
 
 	/* turn y+ off, x- on; we'll use formula #1 */
 	tc->z1 = tsc2007_xfer(tsc, READ_Z1);
-	tc->z2 = tsc2007_xfer(tsc, READ_Z2);
-
-	/* Prepare for next touch reading - power down ADC, enable PENIRQ */
-	tsc2007_xfer(tsc, PWRDOWN);
+	/* Read Z2 and power down ADC after A/D conversion, enable PENIRQ */
+	tc->z2 = tsc2007_xfer(tsc, (TSC2007_POWER_OFF_IRQ_EN | TSC2007_MEASURE_Z2));
 }
 
 u32 tsc2007_calculate_resistance(struct tsc2007 *tsc, struct ts_event *tc)
-- 
2.51.0

Re: [PATCH] Input: touchscreen: tsc2007: Reduce I2C transactions for Z2 read

[Dmitry Torokhov]

Hi Yuki,

On Fri, Apr 10, 2026 at 04:41:00PM +0900, Yuki Horii wrote:
> From: Yuki Horii <yuuki198708@gmail.com>
> 
> The current implementation sends a separate power-down command
> after reading the Z2 value, resulting in an extra I2C
> transaction per measurement cycle.
> 
> The TSC2007 command byte contains a 2-bit power-down mode
> selection field. By selecting the power-down state in the Z2
> measurement command, the device powers down after the Z2 A/D
> conversion completes, eliminating the subsequent power-down
> transaction.
> 
> This reduces the number of I2C transactions by one per touch
> measurement cycle, decreasing I2C bus overhead and improving
> touch sampling performance.
> 
> Signed-off-by: Yuki Horii <yuuki198708@gmail.com>
> ---
>  drivers/input/touchscreen/tsc2007_core.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/input/touchscreen/tsc2007_core.c b/drivers/input/touchscreen/tsc2007_core.c
> index 948935de894b..ff60245baa96 100644
> --- a/drivers/input/touchscreen/tsc2007_core.c
> +++ b/drivers/input/touchscreen/tsc2007_core.c
> @@ -61,10 +61,8 @@ static void tsc2007_read_values(struct tsc2007 *tsc, struct ts_event *tc)
>  
>  	/* turn y+ off, x- on; we'll use formula #1 */
>  	tc->z1 = tsc2007_xfer(tsc, READ_Z1);
> -	tc->z2 = tsc2007_xfer(tsc, READ_Z2);
> -
> -	/* Prepare for next touch reading - power down ADC, enable PENIRQ */
> -	tsc2007_xfer(tsc, PWRDOWN);
> +	/* Read Z2 and power down ADC after A/D conversion, enable PENIRQ */
> +	tc->z2 = tsc2007_xfer(tsc, (TSC2007_POWER_OFF_IRQ_EN | TSC2007_MEASURE_Z2));
>  }
>  
>  u32 tsc2007_calculate_resistance(struct tsc2007 *tsc, struct ts_event *tc)

Thank you for the patch.

I'd like people using this part to chime in (CCed).

Thanks.

-- 
Dmitry