i2c: davinci: fix the cpufreq transition

Commit Message

Bartosz Golaszewski Jan. 22, 2018, 2:42 p.m. UTC

From: Bartosz Golaszewski <[e-mail]>

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 <[e-mail]>
Signed-off-by: Bartosz Golaszewski <[e-mail]>
---
 drivers/i2c/busses/i2c-davinci.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

Comments

Sekhar Nori Jan. 23, 2018, 12:38 p.m. UTC | #1

On Monday 22 January 2018 08:12 PM, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <[e-mail]>
> 
> i2c_davinci_cpufreq_transition() is implemented in a way that will
> block if it ever gets called while no transfer is in progress.

true!

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

reinit_completion() use is must only with complete_all(). At least that
bug is not obvious so needs more detail to be added here.

> 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 <[e-mail]>
> Signed-off-by: Bartosz Golaszewski <[e-mail]>

I assume you tested this on a board where I2C-controlled PMIC changes
voltage during CPUfreq (DA850 LogicPD EVM should have this hardware
support).

Perhaps also add:

Fixes: 82c0de11b734 ("i2c: davinci: Add cpufreq support")

Apart from that:

Reviewed-by: Sekhar Nori <[e-mail]>

Thanks,
Sekhar

David Lechner Jan. 24, 2018, 3:01 a.m. UTC | #2

On 01/22/2018 08:42 AM, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <[e-mail]>
> 
> 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 <[e-mail]>
> Signed-off-by: Bartosz Golaszewski <[e-mail]>
> ---

Tested that it fixes the lockup when there is no active transfer.

Tested-by: David Lechner <[e-mail]>

Wolfram Sang Jan. 24, 2018, 6:15 a.m. UTC | #3

On Mon, Jan 22, 2018 at 03:42:58PM +0100, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <[e-mail]>
> 
> 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 <[e-mail]>
> Signed-off-by: Bartosz Golaszewski <[e-mail]>

Applied to for-next, thanks!

Patch

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);