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

[Yuki Horii <yuuki198708@gmail.com>]

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