lkml.org 
[lkml]   [2019]   [Nov]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 4.19 32/79] i2c: stm32f7: fix a race in slave mode with arbitration loss irq
    Date
    From: Fabrice Gasnier <fabrice.gasnier@st.com>

    [ Upstream commit 6d6b0d0d5afc8c4c84b08261260ba11dfa5206f2 ]

    When in slave mode, an arbitration loss (ARLO) may be detected before the
    slave had a chance to detect the stop condition (STOPF in ISR).
    This is seen when two master + slave adapters switch their roles. It
    provokes the i2c bus to be stuck, busy as SCL line is stretched.
    - the I2C_SLAVE_STOP event is never generated due to STOPF flag is set but
    don't generate an irq (race with ARLO irq, STOPIE is masked). STOPF flag
    remains set until next master xfer (e.g. when STOPIE irq get unmasked).
    In this case, completion is generated too early: immediately upon new
    transfer request (then it doesn't send all data).
    - Some data get stuck in TXDR register. As a consequence, the controller
    stretches the SCL line: the bus gets busy until a future master transfer
    triggers the bus busy / recovery mechanism (this can take time... and
    may never happen at all)

    So choice is to let the STOPF being detected by the slave isr handler,
    to properly handle this stop condition. E.g. don't mask IRQs in error
    handler, when the slave is running.

    Fixes: 60d609f30de2 ("i2c: i2c-stm32f7: Add slave support")
    Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
    Reviewed-by: Pierre-Yves MORDRET <pierre-yves.mordret@st.com>
    Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/i2c/busses/i2c-stm32f7.c | 17 ++++++++++-------
    1 file changed, 10 insertions(+), 7 deletions(-)

    diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
    index 48521bc8a4d23..362b23505f214 100644
    --- a/drivers/i2c/busses/i2c-stm32f7.c
    +++ b/drivers/i2c/busses/i2c-stm32f7.c
    @@ -1488,7 +1488,7 @@ static irqreturn_t stm32f7_i2c_isr_error(int irq, void *data)
    void __iomem *base = i2c_dev->base;
    struct device *dev = i2c_dev->dev;
    struct stm32_i2c_dma *dma = i2c_dev->dma;
    - u32 mask, status;
    + u32 status;

    status = readl_relaxed(i2c_dev->base + STM32F7_I2C_ISR);

    @@ -1513,12 +1513,15 @@ static irqreturn_t stm32f7_i2c_isr_error(int irq, void *data)
    f7_msg->result = -EINVAL;
    }

    - /* Disable interrupts */
    - if (stm32f7_i2c_is_slave_registered(i2c_dev))
    - mask = STM32F7_I2C_XFER_IRQ_MASK;
    - else
    - mask = STM32F7_I2C_ALL_IRQ_MASK;
    - stm32f7_i2c_disable_irq(i2c_dev, mask);
    + if (!i2c_dev->slave_running) {
    + u32 mask;
    + /* Disable interrupts */
    + if (stm32f7_i2c_is_slave_registered(i2c_dev))
    + mask = STM32F7_I2C_XFER_IRQ_MASK;
    + else
    + mask = STM32F7_I2C_ALL_IRQ_MASK;
    + stm32f7_i2c_disable_irq(i2c_dev, mask);
    + }

    /* Disable dma */
    if (i2c_dev->use_dma) {
    --
    2.20.1


    \
     
     \ /
      Last update: 2019-11-08 20:17    [W:3.365 / U:0.016 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site