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    Subject[PATCH] i2c: davinci: fix the cpufreq transition
    Date
    From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

    i2c_davinci_cpufreq_transition() is implemented in a way that will
    block if it ever gets called while no transfer is in progress.

    Not only that, but reinit_completion() is never called for xfr_complete.

    Use the fact that cpufreq uses an srcu_notifier (running in process
    context) for transitions and that the bus_lock is taken during the call
    to master_xfer() and simplify the code by removing the transfer
    completion entirely and protecting i2c_davinci_cpufreq_transition()
    with i2c_lock/unlock_adapter().

    Reported-by: David Lechner <david@lechnology.com>
    Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
    ---
    drivers/i2c/busses/i2c-davinci.c | 12 ++++--------
    1 file changed, 4 insertions(+), 8 deletions(-)

    diff --git a/drivers/i2c/busses/i2c-davinci.c b/drivers/i2c/busses/i2c-davinci.c
    index 2ead9b9eebb7..53ebf0dec1ad 100644
    --- a/drivers/i2c/busses/i2c-davinci.c
    +++ b/drivers/i2c/busses/i2c-davinci.c
    @@ -139,7 +139,6 @@ struct davinci_i2c_dev {
    u8 terminate;
    struct i2c_adapter adapter;
    #ifdef CONFIG_CPU_FREQ
    - struct completion xfr_complete;
    struct notifier_block freq_transition;
    #endif
    struct davinci_i2c_platform_data *pdata;
    @@ -567,9 +566,6 @@ i2c_davinci_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
    }

    ret = num;
    -#ifdef CONFIG_CPU_FREQ
    - complete(&dev->xfr_complete);
    -#endif

    out:
    pm_runtime_mark_last_busy(dev->dev);
    @@ -717,13 +713,15 @@ static int i2c_davinci_cpufreq_transition(struct notifier_block *nb,
    struct davinci_i2c_dev *dev;

    dev = container_of(nb, struct davinci_i2c_dev, freq_transition);
    +
    + i2c_lock_adapter(&dev->adapter);
    if (val == CPUFREQ_PRECHANGE) {
    - wait_for_completion(&dev->xfr_complete);
    davinci_i2c_reset_ctrl(dev, 0);
    } else if (val == CPUFREQ_POSTCHANGE) {
    i2c_davinci_calc_clk_dividers(dev);
    davinci_i2c_reset_ctrl(dev, 1);
    }
    + i2c_unlock_adapter(&dev->adapter);

    return 0;
    }
    @@ -789,9 +787,7 @@ static int davinci_i2c_probe(struct platform_device *pdev)
    }

    init_completion(&dev->cmd_complete);
    -#ifdef CONFIG_CPU_FREQ
    - init_completion(&dev->xfr_complete);
    -#endif
    +
    dev->dev = &pdev->dev;
    dev->irq = irq;
    dev->pdata = dev_get_platdata(&pdev->dev);
    --
    2.15.1
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