target/linux/ipq40xx/patches-4.14/088-0011-i2c-qup-send-NACK-for-last-read-sub-transfers.patch

   1 From f7714b4e451bdcb7918b9aad14af22684ceac638 Mon Sep 17 00:00:00 2001
   2 From: Abhishek Sahu <absahu@codeaurora.org>
   3 Date: Mon, 12 Mar 2018 18:45:00 +0530
   4 Subject: [PATCH 11/13] i2c: qup: send NACK for last read sub transfers
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   8
   9 According to I2c specification, “If a master-receiver sends a
  10 repeated START condition, it sends a not-acknowledge (A) just
  11 before the repeated START condition”. QUP v2 supports sending
  12 of NACK without stop with QUP_TAG_V2_DATARD_NACK so added the
  13 same.
  14
  15 Signed-off-by: Abhishek Sahu <absahu@codeaurora.org>
  16 Reviewed-by: Austin Christ <austinwc@codeaurora.org>
  17 Reviewed-by: Andy Gross <andy.gross@linaro.org>
  18 Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
  19 ---
  20  drivers/i2c/busses/i2c-qup.c | 5 ++++-
  21  1 file changed, 4 insertions(+), 1 deletion(-)
  22
  23 --- a/drivers/i2c/busses/i2c-qup.c
  24 +++ b/drivers/i2c/busses/i2c-qup.c
  25 @@ -104,6 +104,7 @@
  26  #define QUP_TAG_V2_DATAWR              0x82
  27  #define QUP_TAG_V2_DATAWR_STOP         0x83
  28  #define QUP_TAG_V2_DATARD              0x85
  29 +#define QUP_TAG_V2_DATARD_NACK         0x86
  30  #define QUP_TAG_V2_DATARD_STOP         0x87
  31
  32  /* Status, Error flags */
  33 @@ -606,7 +607,9 @@ static int qup_i2c_set_tags(u8 *tags, st
  34                         tags[len++] = QUP_TAG_V2_DATAWR_STOP;
  35         } else {
  36                 if (msg->flags & I2C_M_RD)
  37 -                       tags[len++] = QUP_TAG_V2_DATARD;
  38 +                       tags[len++] = qup->blk.pos == (qup->blk.count - 1) ?
  39 +                                     QUP_TAG_V2_DATARD_NACK :
  40 +                                     QUP_TAG_V2_DATARD;
  41                 else
  42                         tags[len++] = QUP_TAG_V2_DATAWR;
  43         }