git.openwrt.org Git - openwrt/staging/neocturne.git/blob

   1 From 41fa219f0276c70226ac097daaa1b485818bb82a Mon Sep 17 00:00:00 2001
   2 From: Dave Stevenson <dave.stevenson@raspberrypi.com>
   3 Date: Thu, 23 Apr 2020 10:17:18 +0100
   4 Subject: [PATCH] drm/panel/raspberrypi-touchscreen: Use independent
   5  I2C actions with delay.
   6
   7 We now have the hardware I2C controller pinmuxed to the drive the
   8 display I2C, but this controller does not support clock stretching.
   9 The Atmel micro-controller in the panel requires clock stretching
  10 to allow it to prepare any data to be read.
  11
  12 Split the rpi_touchscreen_i2c_read into two independent transactions with
  13 a delay between them for the Atmel to prepare the data.
  14
  15 Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
  16 ---
  17  .../drm/panel/panel-raspberrypi-touchscreen.c | 30 ++++++++++++++++++-
  18  1 file changed, 29 insertions(+), 1 deletion(-)
  19
  20 --- a/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c
  21 +++ b/drivers/gpu/drm/panel/panel-raspberrypi-touchscreen.c
  22 @@ -219,7 +219,35 @@ static struct rpi_touchscreen *panel_to_
  23
  24  static int rpi_touchscreen_i2c_read(struct rpi_touchscreen *ts, u8 reg)
  25  {
  26 -       return i2c_smbus_read_byte_data(ts->i2c, reg);
  27 +       struct i2c_client *client = ts->i2c;
  28 +       struct i2c_msg msgs[1];
  29 +       u8 addr_buf[1] = { reg };
  30 +       u8 data_buf[1] = { 0, };
  31 +       int ret;
  32 +
  33 +       /* Write register address */
  34 +       msgs[0].addr = client->addr;
  35 +       msgs[0].flags = 0;
  36 +       msgs[0].len = ARRAY_SIZE(addr_buf);
  37 +       msgs[0].buf = addr_buf;
  38 +
  39 +       ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
  40 +       if (ret != ARRAY_SIZE(msgs))
  41 +               return -EIO;
  42 +
  43 +       usleep_range(100, 300);
  44 +
  45 +       /* Read data from register */
  46 +       msgs[0].addr = client->addr;
  47 +       msgs[0].flags = I2C_M_RD;
  48 +       msgs[0].len = 1;
  49 +       msgs[0].buf = data_buf;
  50 +
  51 +       ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
  52 +       if (ret != ARRAY_SIZE(msgs))
  53 +               return -EIO;
  54 +
  55 +       return data_buf[0];
  56  }
  57
  58  static void rpi_touchscreen_i2c_write(struct rpi_touchscreen *ts,