target/linux/brcm2708/patches-4.9/0107-i2c-bcm2835-Fix-hang-for-writing-messages-larger-tha.patch

   1 From b302b7c9025334ef6680955a906cee579bf3c85c Mon Sep 17 00:00:00 2001
   2 From: =?UTF-8?q?Noralf=20Tr=C3=B8nnes?= <noralf@tronnes.org>
   3 Date: Sat, 17 Sep 2016 15:07:10 +0200
   4 Subject: [PATCH] i2c: bcm2835: Fix hang for writing messages larger than 16
   5  bytes
   6 MIME-Version: 1.0
   7 Content-Type: text/plain; charset=UTF-8
   8 Content-Transfer-Encoding: 8bit
   9
  10 Writing messages larger than the FIFO size results in a hang, rendering
  11 the machine unusable. This is because the RXD status flag is set on the
  12 first interrupt which results in bcm2835_drain_rxfifo() stealing bytes
  13 from the buffer. The controller continues to trigger interrupts waiting
  14 for the missing bytes, but bcm2835_fill_txfifo() has none to give.
  15 In this situation wait_for_completion_timeout() apparently is unable to
  16 stop the madness.
  17
  18 The BCM2835 ARM Peripherals datasheet has this to say about the flags:
  19   TXD: is set when the FIFO has space for at least one byte of data.
  20   RXD: is set when the FIFO contains at least one byte of data.
  21   TXW: is set during a write transfer and the FIFO is less than full.
  22   RXR: is set during a read transfer and the FIFO is or more full.
  23
  24 Implementing the logic from the downstream i2c-bcm2708 driver solved
  25 the hang problem.
  26
  27 Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
  28 Reviewed-by: Eric Anholt <eric@anholt.net>
  29 Reviewed-by: Martin Sperl <kernel@martin.sperl.org>
  30 ---
  31  drivers/i2c/busses/i2c-bcm2835.c | 22 ++++++++++++++--------
  32  1 file changed, 14 insertions(+), 8 deletions(-)
  33
  34 --- a/drivers/i2c/busses/i2c-bcm2835.c
  35 +++ b/drivers/i2c/busses/i2c-bcm2835.c
  36 @@ -64,6 +64,7 @@ struct bcm2835_i2c_dev {
  37         int irq;
  38         struct i2c_adapter adapter;
  39         struct completion completion;
  40 +       struct i2c_msg *curr_msg;
  41         u32 msg_err;
  42         u8 *msg_buf;
  43         size_t msg_buf_remaining;
  44 @@ -126,14 +127,13 @@ static irqreturn_t bcm2835_i2c_isr(int t
  45                 return IRQ_HANDLED;
  46         }
  47
  48 -       if (val & BCM2835_I2C_S_RXD) {
  49 -               bcm2835_drain_rxfifo(i2c_dev);
  50 -               if (!(val & BCM2835_I2C_S_DONE))
  51 -                       return IRQ_HANDLED;
  52 -       }
  53 -
  54         if (val & BCM2835_I2C_S_DONE) {
  55 -               if (i2c_dev->msg_buf_remaining)
  56 +               if (i2c_dev->curr_msg->flags & I2C_M_RD) {
  57 +                       bcm2835_drain_rxfifo(i2c_dev);
  58 +                       val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
  59 +               }
  60 +
  61 +               if ((val & BCM2835_I2C_S_RXD) || i2c_dev->msg_buf_remaining)
  62                         i2c_dev->msg_err = BCM2835_I2C_S_LEN;
  63                 else
  64                         i2c_dev->msg_err = 0;
  65 @@ -141,11 +141,16 @@ static irqreturn_t bcm2835_i2c_isr(int t
  66                 return IRQ_HANDLED;
  67         }
  68
  69 -       if (val & BCM2835_I2C_S_TXD) {
  70 +       if (val & BCM2835_I2C_S_TXW) {
  71                 bcm2835_fill_txfifo(i2c_dev);
  72                 return IRQ_HANDLED;
  73         }
  74
  75 +       if (val & BCM2835_I2C_S_RXR) {
  76 +               bcm2835_drain_rxfifo(i2c_dev);
  77 +               return IRQ_HANDLED;
  78 +       }
  79 +
  80         return IRQ_NONE;
  81  }
  82
  83 @@ -155,6 +160,7 @@ static int bcm2835_i2c_xfer_msg(struct b
  84         u32 c;
  85         unsigned long time_left;
  86
  87 +       i2c_dev->curr_msg = msg;
  88         i2c_dev->msg_buf = msg->buf;
  89         i2c_dev->msg_buf_remaining = msg->len;
  90         reinit_completion(&i2c_dev->completion);