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    SubjectRe: [PATCH V3 1/2] i2c-designware: Add i2c bus locking support
    On Mon, Dec 01, 2014 at 04:09:32PM -0800, David E. Box wrote:
    > Adds support for acquiring and releasing a hardware bus lock in the i2c
    > designware core transfer function. This is needed for i2c bus controllers
    > that are shared with but not controlled by the kernel.
    >
    > Signed-off-by: David E. Box <david.e.box@linux.intel.com>
    > ---
    > drivers/i2c/busses/i2c-designware-core.c | 11 +++++++++++
    > drivers/i2c/busses/i2c-designware-core.h | 6 ++++++
    > drivers/i2c/busses/i2c-designware-platdrv.c | 18 +++++++++++++-----
    > 3 files changed, 30 insertions(+), 5 deletions(-)
    >
    > diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
    > index 3c20e4b..377deeb 100644
    > --- a/drivers/i2c/busses/i2c-designware-core.c
    > +++ b/drivers/i2c/busses/i2c-designware-core.c
    > @@ -631,6 +631,14 @@ i2c_dw_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
    > dev->abort_source = 0;
    > dev->rx_outstanding = 0;
    >
    > + if (dev->acquire_lock) {
    > + ret = dev->acquire_lock(dev);
    > + if (ret) {
    > + dev_err(dev->dev, "couldn't acquire bus ownership\n");
    > + goto done;

    I wonder what happens now since you failed to acquire the lock...

    > + }
    > + }
    > +
    > ret = i2c_dw_wait_bus_not_busy(dev);
    > if (ret < 0)
    > goto done;
    > @@ -676,6 +684,9 @@ i2c_dw_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
    > ret = -EIO;
    >
    > done:
    > + if (dev->release_lock)
    > + dev->release_lock(dev);

    ... but here you unconditionally release it?

    Otherwise the patch looks good to me.

    > +
    > pm_runtime_mark_last_busy(dev->dev);
    > pm_runtime_put_autosuspend(dev->dev);
    > mutex_unlock(&dev->lock);
    > diff --git a/drivers/i2c/busses/i2c-designware-core.h b/drivers/i2c/busses/i2c-designware-core.h
    > index d66b6cb..a472c91 100644
    > --- a/drivers/i2c/busses/i2c-designware-core.h
    > +++ b/drivers/i2c/busses/i2c-designware-core.h
    > @@ -65,6 +65,9 @@
    > * @ss_lcnt: standard speed LCNT value
    > * @fs_hcnt: fast speed HCNT value
    > * @fs_lcnt: fast speed LCNT value
    > + * @acquire_lock: function to acquire a hardware lock on the bus
    > + * @release_lock: function to release a hardware lock on the bus
    > + * @pm_runtime_disabled: true if pm runtime is disabled
    > *
    > * HCNT and LCNT parameters can be used if the platform knows more accurate
    > * values than the one computed based only on the input clock frequency.
    > @@ -105,6 +108,9 @@ struct dw_i2c_dev {
    > u16 ss_lcnt;
    > u16 fs_hcnt;
    > u16 fs_lcnt;
    > + int (*acquire_lock)(struct dw_i2c_dev *dev);
    > + void (*release_lock)(struct dw_i2c_dev *dev);
    > + bool pm_runtime_disabled;
    > };
    >
    > #define ACCESS_SWAP 0x00000001
    > diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
    > index a743115..afdff3b 100644
    > --- a/drivers/i2c/busses/i2c-designware-platdrv.c
    > +++ b/drivers/i2c/busses/i2c-designware-platdrv.c
    > @@ -261,10 +261,16 @@ static int dw_i2c_probe(struct platform_device *pdev)
    > return r;
    > }
    >
    > - pm_runtime_set_autosuspend_delay(&pdev->dev, 1000);
    > - pm_runtime_use_autosuspend(&pdev->dev);
    > - pm_runtime_set_active(&pdev->dev);
    > - pm_runtime_enable(&pdev->dev);
    > + i2c_dw_eval_lock_support(dev);
    > +
    > + if (dev->pm_runtime_disabled) {
    > + pm_runtime_forbid(&pdev->dev);
    > + } else {
    > + pm_runtime_set_autosuspend_delay(&pdev->dev, 1000);
    > + pm_runtime_use_autosuspend(&pdev->dev);
    > + pm_runtime_set_active(&pdev->dev);
    > + pm_runtime_enable(&pdev->dev);
    > + }
    >
    > return 0;
    > }
    > @@ -314,7 +320,9 @@ static int dw_i2c_resume(struct device *dev)
    > struct dw_i2c_dev *i_dev = platform_get_drvdata(pdev);
    >
    > clk_prepare_enable(i_dev->clk);
    > - i2c_dw_init(i_dev);
    > +
    > + if (!i_dev->pm_runtime_disabled)
    > + i2c_dw_init(i_dev);
    >
    > return 0;
    > }
    > --
    > 1.9.1


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