[PATCH v1] mfd: tps6586x: Move interrupt handling into workqueue

[PATCH v1] mfd: tps6586x: Move interrupt handling into workqueue

[Dmitry Osipenko]

Reading of status register within the interrupt handler fails with -EAGAIN
if I2C is busy with handling some other request at the same time. Move the
actual interrupt handling into a workqueue to avoid the unfortunate I2C
failure and to avoid hanging CPU in interrupt up to 1 second (transfer
timeout in the Tegra I2C driver).

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/mfd/tps6586x.c | 40 +++++++++++++++++++++++++++++-----------
 1 file changed, 29 insertions(+), 11 deletions(-)

diff --git a/drivers/mfd/tps6586x.c b/drivers/mfd/tps6586x.c
index b89379782741..9896e080b274 100644
--- a/drivers/mfd/tps6586x.c
+++ b/drivers/mfd/tps6586x.c
@@ -133,6 +133,7 @@ struct tps6586x {
 	u32			irq_en;
 	u8			mask_reg[5];
 	struct irq_domain	*irq_domain;
+	struct work_struct	isr_work;
 };
 
 static inline struct tps6586x *dev_to_tps6586x(struct device *dev)
@@ -309,18 +310,19 @@ static const struct irq_domain_ops tps6586x_domain_ops = {
 	.xlate  = irq_domain_xlate_twocell,
 };
 
-static irqreturn_t tps6586x_irq(int irq, void *data)
+static void tps6586x_isr_work(struct work_struct *work)
 {
-	struct tps6586x *tps6586x = data;
+	struct tps6586x *tps6586x = container_of(work, struct tps6586x,
+						 isr_work);
 	u32 acks;
-	int ret = 0;
+	int err;
 
-	ret = tps6586x_reads(tps6586x->dev, TPS6586X_INT_ACK1,
+	err = tps6586x_reads(tps6586x->dev, TPS6586X_INT_ACK1,
 			     sizeof(acks), (uint8_t *)&acks);
-
-	if (ret < 0) {
-		dev_err(tps6586x->dev, "failed to read interrupt status\n");
-		return IRQ_NONE;
+	if (err < 0) {
+		dev_err(tps6586x->dev,
+			"failed to read interrupt status %d\n", err);
+		return;
 	}
 
 	acks = le32_to_cpu(acks);
@@ -335,6 +337,16 @@ static irqreturn_t tps6586x_irq(int irq, void *data)
 		acks &= ~(1 << i);
 	}
 
+	enable_irq(tps6586x->irq);
+}
+
+static irqreturn_t tps6586x_irq(int irq, void *data)
+{
+	struct tps6586x *tps6586x = data;
+
+	disable_irq_nosync(irq);
+	schedule_work(&tps6586x->isr_work);
+
 	return IRQ_HANDLED;
 }
 
@@ -542,8 +554,9 @@ static int tps6586x_i2c_probe(struct i2c_client *client,
 		return ret;
 	}
 
-
 	if (client->irq) {
+		INIT_WORK(&tps6586x->isr_work, tps6586x_isr_work);
+
 		ret = tps6586x_irq_init(tps6586x, client->irq,
 					pdata->irq_base);
 		if (ret) {
@@ -585,10 +598,15 @@ static int tps6586x_i2c_remove(struct i2c_client *client)
 {
 	struct tps6586x *tps6586x = i2c_get_clientdata(client);
 
+	if (client->irq) {
+		disable_irq(client->irq);
+		flush_work(&tps6586x->isr_work);
+		free_irq(client->irq, tps6586x);
+	}
+
 	tps6586x_remove_subdevs(tps6586x);
 	mfd_remove_devices(tps6586x->dev);
-	if (client->irq)
-		free_irq(client->irq, tps6586x);
+
 	return 0;
 }
 
-- 
2.17.0

Re: [PATCH v1] mfd: tps6586x: Move interrupt handling into workqueue

[Thierry Reding]

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On Mon, May 14, 2018 at 12:18:42AM +0300, Dmitry Osipenko wrote:
> Reading of status register within the interrupt handler fails with -EAGAIN
> if I2C is busy with handling some other request at the same time. Move the
> actual interrupt handling into a workqueue to avoid the unfortunate I2C
> failure and to avoid hanging CPU in interrupt up to 1 second (transfer
> timeout in the Tegra I2C driver).
> 
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
>  drivers/mfd/tps6586x.c | 40 +++++++++++++++++++++++++++++-----------
>  1 file changed, 29 insertions(+), 11 deletions(-)

Could this not be achieved with a threaded interrupt handler?

Thierry

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Re: [PATCH v1] mfd: tps6586x: Move interrupt handling into workqueue

[Dmitry Osipenko]

On 14.05.2018 14:51, Thierry Reding wrote:
> On Mon, May 14, 2018 at 12:18:42AM +0300, Dmitry Osipenko wrote:
>> Reading of status register within the interrupt handler fails with -EAGAIN
>> if I2C is busy with handling some other request at the same time. Move the
>> actual interrupt handling into a workqueue to avoid the unfortunate I2C
>> failure and to avoid hanging CPU in interrupt up to 1 second (transfer
>> timeout in the Tegra I2C driver).
>>
>> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
>> ---
>>  drivers/mfd/tps6586x.c | 40 +++++++++++++++++++++++++++++-----------
>>  1 file changed, 29 insertions(+), 11 deletions(-)
> 
> Could this not be achieved with a threaded interrupt handler?
> 
> Thierry
> 

Seems yes. I completely forgot about the threaded interrupt handlers existence.
Thank you very much for the suggestion, I'll try with the threaded IRQ and send
v2 if it will be fine.

Re: [PATCH v1] mfd: tps6586x: Move interrupt handling into workqueue

[Dmitry Osipenko]

On 14.05.2018 15:01, Dmitry Osipenko wrote:
> On 14.05.2018 14:51, Thierry Reding wrote:
>> On Mon, May 14, 2018 at 12:18:42AM +0300, Dmitry Osipenko wrote:
>>> Reading of status register within the interrupt handler fails with -EAGAIN
>>> if I2C is busy with handling some other request at the same time. Move the
>>> actual interrupt handling into a workqueue to avoid the unfortunate I2C
>>> failure and to avoid hanging CPU in interrupt up to 1 second (transfer
>>> timeout in the Tegra I2C driver).
>>>
>>> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
>>> ---
>>>  drivers/mfd/tps6586x.c | 40 +++++++++++++++++++++++++++++-----------
>>>  1 file changed, 29 insertions(+), 11 deletions(-)
>>
>> Could this not be achieved with a threaded interrupt handler?
>>
>> Thierry
>>
> 
> Seems yes. I completely forgot about the threaded interrupt handlers existence.
> Thank you very much for the suggestion, I'll try with the threaded IRQ and send
> v2 if it will be fine.
> 

Oh wait! TPS6586x driver already uses threaded interrupt handler, so everything
should be fine in regards to the interrupt handling and this patch is obsolete.
Thank you again for the good suggestion, then it's only the Tegra's I2C driver
that causes trouble for the TPS6586x right now.

Re: [PATCH v1] mfd: tps6586x: Move interrupt handling into workqueue

[Thierry Reding]

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On Mon, May 14, 2018 at 03:20:55PM +0300, Dmitry Osipenko wrote:
> On 14.05.2018 15:01, Dmitry Osipenko wrote:
> > On 14.05.2018 14:51, Thierry Reding wrote:
> >> On Mon, May 14, 2018 at 12:18:42AM +0300, Dmitry Osipenko wrote:
> >>> Reading of status register within the interrupt handler fails with -EAGAIN
> >>> if I2C is busy with handling some other request at the same time. Move the
> >>> actual interrupt handling into a workqueue to avoid the unfortunate I2C
> >>> failure and to avoid hanging CPU in interrupt up to 1 second (transfer
> >>> timeout in the Tegra I2C driver).
> >>>
> >>> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> >>> ---
> >>>  drivers/mfd/tps6586x.c | 40 +++++++++++++++++++++++++++++-----------
> >>>  1 file changed, 29 insertions(+), 11 deletions(-)
> >>
> >> Could this not be achieved with a threaded interrupt handler?
> >>
> >> Thierry
> >>
> > 
> > Seems yes. I completely forgot about the threaded interrupt handlers existence.
> > Thank you very much for the suggestion, I'll try with the threaded IRQ and send
> > v2 if it will be fine.
> > 
> 
> Oh wait! TPS6586x driver already uses threaded interrupt handler, so everything
> should be fine in regards to the interrupt handling and this patch is obsolete.
> Thank you again for the good suggestion, then it's only the Tegra's I2C driver
> that causes trouble for the TPS6586x right now.

Heh... indeed. Sounds like the discussion that Wolfram pointed out is
the right way forward.

Thierry

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