Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756136Ab1DSWPI (ORCPT ); Tue, 19 Apr 2011 18:15:08 -0400 Received: from smtp-out.google.com ([74.125.121.67]:10146 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753713Ab1DSWPG (ORCPT ); Tue, 19 Apr 2011 18:15:06 -0400 From: Vincent Palatin To: Jean Delvare , Ben Dooks , linux-i2c@vger.kernel.org Cc: Olof Johansson , linux-kernel@vger.kernel.org, Colin Cross , linux-tegra@vger.kernel.org, Vincent Palatin Subject: [PATCH] i2c: i2c-tegra: fix possible race condition after tx Date: Tue, 19 Apr 2011 18:14:36 -0400 Message-Id: <1303251276-18768-1-git-send-email-vpalatin@chromium.org> X-Mailer: git-send-email 1.7.3.1 X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6460 Lines: 181 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. Of course, this is unlikely since the I2C bus is slow and thus the ISR is called several hundreds of microseconds after the last register write. Signed-off-by: Vincent Palatin --- drivers/i2c/busses/i2c-tegra.c | 54 ++++++++++++++++++++++----------------- 1 files changed, 30 insertions(+), 24 deletions(-) diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c index b4ab39b..c1b119b 100644 --- a/drivers/i2c/busses/i2c-tegra.c +++ b/drivers/i2c/busses/i2c-tegra.c @@ -125,7 +125,7 @@ struct tegra_i2c_dev { struct completion msg_complete; int msg_err; u8 *msg_buf; - size_t msg_buf_remaining; + atomic_t msg_buf_remaining; int msg_read; unsigned long bus_clk_rate; bool is_suspended; @@ -213,38 +213,41 @@ static int tegra_i2c_empty_rx_fifo(struct tegra_i2c_dev *i2c_dev) u32 val; int rx_fifo_avail; u8 *buf = i2c_dev->msg_buf; - size_t buf_remaining = i2c_dev->msg_buf_remaining; int words_to_transfer; + int bytes_to_transfer; val = i2c_readl(i2c_dev, I2C_FIFO_STATUS); rx_fifo_avail = (val & I2C_FIFO_STATUS_RX_MASK) >> I2C_FIFO_STATUS_RX_SHIFT; /* Rounds down to not include partial word at the end of buf */ - words_to_transfer = buf_remaining / BYTES_PER_FIFO_WORD; + words_to_transfer = atomic_read(&i2c_dev->msg_buf_remaining) / + BYTES_PER_FIFO_WORD; if (words_to_transfer > rx_fifo_avail) words_to_transfer = rx_fifo_avail; + atomic_sub(words_to_transfer * BYTES_PER_FIFO_WORD, + &i2c_dev->msg_buf_remaining); i2c_readsl(i2c_dev, buf, I2C_RX_FIFO, words_to_transfer); buf += words_to_transfer * BYTES_PER_FIFO_WORD; - buf_remaining -= words_to_transfer * BYTES_PER_FIFO_WORD; rx_fifo_avail -= words_to_transfer; /* * If there is a partial word at the end of buf, handle it manually to * prevent overwriting past the end of buf */ - if (rx_fifo_avail > 0 && buf_remaining > 0) { - BUG_ON(buf_remaining > 3); + bytes_to_transfer = atomic_read(&i2c_dev->msg_buf_remaining); + if (rx_fifo_avail > 0 && bytes_to_transfer > 0) { + BUG_ON(bytes_to_transfer > 3); + atomic_set(&i2c_dev->msg_buf_remaining, 0); val = i2c_readl(i2c_dev, I2C_RX_FIFO); - memcpy(buf, &val, buf_remaining); - buf_remaining = 0; + memcpy(buf, &val, bytes_to_transfer); rx_fifo_avail--; } - BUG_ON(rx_fifo_avail > 0 && buf_remaining > 0); - i2c_dev->msg_buf_remaining = buf_remaining; + BUG_ON(rx_fifo_avail > 0 && + atomic_read(&i2c_dev->msg_buf_remaining) > 0); i2c_dev->msg_buf = buf; return 0; } @@ -254,22 +257,24 @@ static int tegra_i2c_fill_tx_fifo(struct tegra_i2c_dev *i2c_dev) u32 val; int tx_fifo_avail; u8 *buf = i2c_dev->msg_buf; - size_t buf_remaining = i2c_dev->msg_buf_remaining; int words_to_transfer; + int bytes_to_transfer; val = i2c_readl(i2c_dev, I2C_FIFO_STATUS); tx_fifo_avail = (val & I2C_FIFO_STATUS_TX_MASK) >> I2C_FIFO_STATUS_TX_SHIFT; /* Rounds down to not include partial word at the end of buf */ - words_to_transfer = buf_remaining / BYTES_PER_FIFO_WORD; + words_to_transfer = atomic_read(&i2c_dev->msg_buf_remaining) / + BYTES_PER_FIFO_WORD; if (words_to_transfer > tx_fifo_avail) words_to_transfer = tx_fifo_avail; + atomic_sub(words_to_transfer * BYTES_PER_FIFO_WORD, + &i2c_dev->msg_buf_remaining); 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; /* @@ -277,16 +282,17 @@ static int tegra_i2c_fill_tx_fifo(struct tegra_i2c_dev *i2c_dev) * prevent reading past the end of buf, which could cross a page * boundary and fault. */ - if (tx_fifo_avail > 0 && buf_remaining > 0) { - BUG_ON(buf_remaining > 3); - memcpy(&val, buf, buf_remaining); + bytes_to_transfer = atomic_read(&i2c_dev->msg_buf_remaining); + if (tx_fifo_avail > 0 && bytes_to_transfer > 0) { + BUG_ON(bytes_to_transfer > 3); + memcpy(&val, buf, bytes_to_transfer); + atomic_set(&i2c_dev->msg_buf_remaining, 0); 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; + BUG_ON(tx_fifo_avail > 0 && + atomic_read(&i2c_dev->msg_buf_remaining) > 0); i2c_dev->msg_buf = buf; return 0; } @@ -364,21 +370,21 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id) } if (i2c_dev->msg_read && (status & I2C_INT_RX_FIFO_DATA_REQ)) { - if (i2c_dev->msg_buf_remaining) + if (atomic_read(&i2c_dev->msg_buf_remaining)) tegra_i2c_empty_rx_fifo(i2c_dev); else BUG(); } if (!i2c_dev->msg_read && (status & I2C_INT_TX_FIFO_DATA_REQ)) { - if (i2c_dev->msg_buf_remaining) + if (atomic_read(&i2c_dev->msg_buf_remaining)) tegra_i2c_fill_tx_fifo(i2c_dev); else tegra_i2c_mask_irq(i2c_dev, I2C_INT_TX_FIFO_DATA_REQ); } if ((status & I2C_INT_PACKET_XFER_COMPLETE) && - !i2c_dev->msg_buf_remaining) + !atomic_read(&i2c_dev->msg_buf_remaining)) complete(&i2c_dev->msg_complete); i2c_writel(i2c_dev, status, I2C_INT_STATUS); @@ -408,7 +414,7 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev, return -EINVAL; i2c_dev->msg_buf = msg->buf; - i2c_dev->msg_buf_remaining = msg->len; + atomic_set(&i2c_dev->msg_buf_remaining, msg->len); i2c_dev->msg_err = I2C_ERR_NONE; i2c_dev->msg_read = (msg->flags & I2C_M_RD); INIT_COMPLETION(i2c_dev->msg_complete); @@ -440,7 +446,7 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev, int_mask = I2C_INT_NO_ACK | I2C_INT_ARBITRATION_LOST; if (msg->flags & I2C_M_RD) int_mask |= I2C_INT_RX_FIFO_DATA_REQ; - else if (i2c_dev->msg_buf_remaining) + else if (atomic_read(&i2c_dev->msg_buf_remaining)) int_mask |= I2C_INT_TX_FIFO_DATA_REQ; tegra_i2c_unmask_irq(i2c_dev, int_mask); dev_dbg(i2c_dev->dev, "unmasked irq: %02x\n", -- 1.7.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/