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From a8bb5f5ddbef4ac5b0e256c7c3bde4ac5636f429 Mon Sep 17 00:00:00 2001
From: Dave Stevenson <dave.stevenson@raspberrypi.com>
Date: Wed, 8 Sep 2021 14:21:38 +0100
Subject: [PATCH] drm/panel/raspberrypi-touchscreen: Handle I2C errors.
rpi_touchscreen_i2c_read returns any errors from i2c_transfer,
or the 8 bit received value.
Check for error values before trying to process the data as
valid.
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
---
drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
--- a/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c
+++ b/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c
@@ -296,13 +296,14 @@ static int rpi_touchscreen_noop(struct d
static int rpi_touchscreen_prepare(struct drm_panel *panel)
{
struct rpi_touchscreen *ts = panel_to_ts(panel);
- int i;
+ int i, data;
rpi_touchscreen_i2c_write(ts, REG_POWERON, 1);
usleep_range(20000, 25000);
/* Wait for nPWRDWN to go low to indicate poweron is done. */
for (i = 0; i < 100; i++) {
- if (rpi_touchscreen_i2c_read(ts, REG_PORTB) & 1)
+ data = rpi_touchscreen_i2c_read(ts, REG_PORTB);
+ if (data >= 0 && (data & 1))
break;
}
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