From: Doug Anderson <[email protected]> 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 <[email protected]> Tested-by: Vincent Palatin <[email protected]> Acked-by: Rhyland Klein <[email protected]> Acked-by: Stephen Warren <[email protected]> Signed-off-by: Stephen Warren <[email protected]> --- 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 _______________________________________________ devicetree-discuss mailing list [email protected] https://lists.ozlabs.org/listinfo/devicetree-discuss
