linux-kernel - [RESEND PATCH 3/3] input: ti_am335x_tsc: lower the X and Y sampling time

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Date:   Sun, 12 Dec 2021 13:53:58 +0100
From:   Dario Binacchi <dariobin@...ero.it>
To:     linux-kernel@...r.kernel.org
Cc:     "Andrew F . Davis" <afd@...com>, Felipe Balbi <balbi@...com>,
        Rachna Patil <rachna@...com>, Wolfram Sang <wsa@...nel.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        linux-input@...r.kernel.org, Jeff Lance <j-lance1@...com>,
        Zubair Lutfullah <zubair.lutfullah@...il.com>,
        Vignesh R <vigneshr@...com>, Dave Gerlach <d-gerlach@...com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Brad Griffis <bgriffis@...com>,
        Dario Binacchi <dariobin@...ero.it>
Subject: [RESEND PATCH 3/3] input: ti_am335x_tsc: lower the X and Y sampling time

The open delay time has to be applied only on the first sample of the
X/Y coordinates because on the following samples the ADC channel is not
changed. Removing this time from the samples after the first one,
"ti,coordinate-readouts" greater than 1, decreases the total acquisition
time, allowing to increase the number of acquired coordinates in the time
unit.

Signed-off-by: Dario Binacchi <dariobin@...ero.it>

---

 drivers/input/touchscreen/ti_am335x_tsc.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/input/touchscreen/ti_am335x_tsc.c b/drivers/input/touchscreen/ti_am335x_tsc.c
index cfc943423241..f4ef218bc1b8 100644
--- a/drivers/input/touchscreen/ti_am335x_tsc.c
+++ b/drivers/input/touchscreen/ti_am335x_tsc.c
@@ -126,7 +126,7 @@ static int titsc_config_wires(struct titsc *ts_dev)
 static void titsc_step_config(struct titsc *ts_dev)
 {
 	unsigned int	config;
-	int i;
+	int i, n;
 	int end_step, first_step, tsc_steps;
 	u32 stepenable;
 
@@ -151,9 +151,11 @@ static void titsc_step_config(struct titsc *ts_dev)
 	first_step = TOTAL_STEPS - tsc_steps;
 	/* Steps 16 to 16-coordinate_readouts is for X */
 	end_step = first_step + tsc_steps;
+	n = 0;
 	for (i = end_step - ts_dev->coordinate_readouts; i < end_step; i++) {
 		titsc_writel(ts_dev, REG_STEPCONFIG(i), config);
-		titsc_writel(ts_dev, REG_STEPDELAY(i), STEPCONFIG_OPENDLY);
+		titsc_writel(ts_dev, REG_STEPDELAY(i),
+			     n++ == 0 ? STEPCONFIG_OPENDLY : 0);
 	}
 
 	config = 0;
@@ -175,9 +177,11 @@ static void titsc_step_config(struct titsc *ts_dev)
 
 	/* 1 ... coordinate_readouts is for Y */
 	end_step = first_step + ts_dev->coordinate_readouts;
+	n = 0;
 	for (i = first_step; i < end_step; i++) {
 		titsc_writel(ts_dev, REG_STEPCONFIG(i), config);
-		titsc_writel(ts_dev, REG_STEPDELAY(i), STEPCONFIG_OPENDLY);
+		titsc_writel(ts_dev, REG_STEPDELAY(i),
+			     n++ == 0 ? STEPCONFIG_OPENDLY : 0);
 	}
 
 	/* Make CHARGECONFIG same as IDLECONFIG */
-- 
2.17.1