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i2c: davinci: fix the cpufreq transition

PATCH Applied Bartosz Golaszewski 4 participants 4 messages Jan 22, 2018 – Jan 24, 2018

Subsystems (2)
I2C subsystem host drivers TI DaVinci machine support
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Bartosz Golaszewski

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#0 lore raw

PATCH 1/1 i2c: davinci: fix the cpufreq transition

From: Bartosz Golaszewski <[email protected]>

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 <[email protected]>
Signed-off-by Bartosz Golaszewski <[email protected]>
---
 drivers/i2c/busses/i2c-davinci.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)
drivers/i2c/busses/i2c-davinci.c +4 -8
index 2ead9b9eebb7..53ebf0dec1ad 100644
@@ -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);
Signature · 1 line
2.15.1
Reviewed-by on v1 1/1
#1 lore raw
Quoted 4 lines · Bartosz Golaszewski

From: Bartosz Golaszewski <[email protected]>

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

true!

Quoted 2 lines

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.

Quoted 8 lines

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 <[email protected]>
Signed-off-by Bartosz Golaszewski <[email protected]>

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 <[email protected]>

Thanks,
Sekhar

Tested-by on v1 1/1
#2 lore raw
In reply to Bartosz Golaszewski
Quoted 13 lines · Bartosz Golaszewski

From: Bartosz Golaszewski <[email protected]>

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().

Quoted 3 lines
Reported-by David Lechner <[email protected]>
Signed-off-by Bartosz Golaszewski <[email protected]>

---

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

Tested-by David Lechner <[email protected]>
Applied
#3 lore raw
In reply to Bartosz Golaszewski
Quoted 7 lines · Bartosz Golaszewski

From: Bartosz Golaszewski <[email protected]>

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.

Quoted 8 lines

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 <[email protected]>
Signed-off-by Bartosz Golaszewski <[email protected]>

Applied to for-next, thanks!

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