[PATCH V3 1/2] i2c-designware: Add i2c bus locking support

["David E. Box" <david.e.box@xxxxxxxxxxxxxxx>]

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@xxxxxxxxxxxxxxx>
---
 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;
+		}
+	}
+
 	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);
+
 	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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