From: Doug Anderson <dianders@xxxxxxxxxxxx>
In tegra_i2c_fill_tx_fifo, once we have finished pushing all the bytes
to the I2C hardware controller, the interrupt might happen before we
have updated i2c_dev->msg_buf_remaining at the end of the function.
Then, in tegra_i2c_isr, we will call again tegra_i2c_fill_tx_fifo
triggering weird behaviour. This has been shown to happen under real
conditions.
Signed-off-by: Doug Anderson <dianders@xxxxxxxxxxxx>
Tested-by: Vincent Palatin <vpalatin@xxxxxxxxxxxx>
Acked-by: Rhyland Klein <rklein@xxxxxxxxxx>
Acked-by: Stephen Warren <swarren@xxxxxxxxxx>
Signed-off-by: Stephen Warren <swarren@xxxxxxxxxx>
---
drivers/i2c/busses/i2c-tegra.c | 46 +++++++++++++++++++++++++++------------
1 files changed, 32 insertions(+), 14 deletions(-)
diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 8848a4b..b402435 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -271,14 +271,30 @@ static int tegra_i2c_fill_tx_fifo(struct tegra_i2c_dev *i2c_dev)
/* Rounds down to not include partial word at the end of buf */
words_to_transfer = buf_remaining / BYTES_PER_FIFO_WORD;
- if (words_to_transfer > tx_fifo_avail)
- words_to_transfer = tx_fifo_avail;
- i2c_writesl(i2c_dev, buf, I2C_TX_FIFO, words_to_transfer);
-
- buf += words_to_transfer * BYTES_PER_FIFO_WORD;
- buf_remaining -= words_to_transfer * BYTES_PER_FIFO_WORD;
- tx_fifo_avail -= words_to_transfer;
+ /* It's very common to have < 4 bytes, so optimize that case. */
+ if (words_to_transfer) {
+ if (words_to_transfer > tx_fifo_avail)
+ words_to_transfer = tx_fifo_avail;
+
+ /*
+ * Update state before writing to FIFO. If this casues us
+ * to finish writing all bytes (AKA buf_remaining goes to 0) we
+ * have a potential for an interrupt (PACKET_XFER_COMPLETE is
+ * not maskable). We need to make sure that the isr sees
+ * buf_remaining as 0 and doesn't call us back re-entrantly.
+ */
+ buf_remaining -= words_to_transfer * BYTES_PER_FIFO_WORD;
+ tx_fifo_avail -= words_to_transfer;
+ i2c_dev->msg_buf_remaining = buf_remaining;
+ i2c_dev->msg_buf = buf +
+ words_to_transfer * BYTES_PER_FIFO_WORD;
+ barrier();
+
+ i2c_writesl(i2c_dev, buf, I2C_TX_FIFO, words_to_transfer);
+
+ buf += words_to_transfer * BYTES_PER_FIFO_WORD;
+ }
/*
* If there is a partial word at the end of buf, handle it manually to
@@ -288,14 +304,15 @@ static int tegra_i2c_fill_tx_fifo(struct tegra_i2c_dev *i2c_dev)
if (tx_fifo_avail > 0 && buf_remaining > 0) {
BUG_ON(buf_remaining > 3);
memcpy(&val, buf, buf_remaining);
+
+ /* Again update before writing to FIFO to make sure isr sees. */
+ i2c_dev->msg_buf_remaining = 0;
+ i2c_dev->msg_buf = NULL;
+ barrier();
+
i2c_writel(i2c_dev, val, I2C_TX_FIFO);
- buf_remaining = 0;
- tx_fifo_avail--;
}
- BUG_ON(tx_fifo_avail > 0 && buf_remaining > 0);
- i2c_dev->msg_buf_remaining = buf_remaining;
- i2c_dev->msg_buf = buf;
return 0;
}
@@ -412,9 +429,10 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
tegra_i2c_mask_irq(i2c_dev, I2C_INT_TX_FIFO_DATA_REQ);
}
- if ((status & I2C_INT_PACKET_XFER_COMPLETE) &&
- !i2c_dev->msg_buf_remaining)
+ if (status & I2C_INT_PACKET_XFER_COMPLETE) {
+ BUG_ON(i2c_dev->msg_buf_remaining);
complete(&i2c_dev->msg_complete);
+ }
i2c_writel(i2c_dev, status, I2C_INT_STATUS);
if (i2c_dev->is_dvc)
--
1.7.0.4
--
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