target/linux/bcm27xx/patches-5.15/950-0478-drm-panel-raspberrypi-touchscreen-Handle-I2C-errors.patch

   1 From a8bb5f5ddbef4ac5b0e256c7c3bde4ac5636f429 Mon Sep 17 00:00:00 2001
   2 From: Dave Stevenson <dave.stevenson@raspberrypi.com>
   3 Date: Wed, 8 Sep 2021 14:21:38 +0100
   4 Subject: [PATCH] drm/panel/raspberrypi-touchscreen: Handle I2C errors.
   5
   6 rpi_touchscreen_i2c_read returns any errors from i2c_transfer,
   7 or the 8 bit received value.
   8 Check for error values before trying to process the data as
   9 valid.
  10
  11 Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
  12 ---
  13  drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c | 5 +++--
  14  1 file changed, 3 insertions(+), 2 deletions(-)
  15
  16 --- a/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c
  17 +++ b/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c
  18 @@ -296,13 +296,14 @@ static int rpi_touchscreen_noop(struct d
  19  static int rpi_touchscreen_prepare(struct drm_panel *panel)
  20  {
  21         struct rpi_touchscreen *ts = panel_to_ts(panel);
  22 -       int i;
  23 +       int i, data;
  24
  25         rpi_touchscreen_i2c_write(ts, REG_POWERON, 1);
  26         usleep_range(20000, 25000);
  27         /* Wait for nPWRDWN to go low to indicate poweron is done. */
  28         for (i = 0; i < 100; i++) {
  29 -               if (rpi_touchscreen_i2c_read(ts, REG_PORTB) & 1)
  30 +               data = rpi_touchscreen_i2c_read(ts, REG_PORTB);
  31 +               if (data >= 0 && (data & 1))
  32                         break;
  33         }
  34