Re: [PATCH 2/3] Input: zforce - enable irq only if we are ready to process it

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Mon, Jul 20, 2015 at 07:19:21AM +0200, external.Oleksij.Rempel wrote:
> Hi Dmitry,
> 
> 
> On 17.07.2015 23:58, Dmitry Torokhov wrote:
> >Hi Oleksij,
> >
> >On Tue, Jul 14, 2015 at 08:40:47AM +0200, external.Oleksij.Rempel wrote:
> >>Hi Dmitry,
> >>
> >>On 13.07.2015 19:07, Dmitry Torokhov wrote:
> >>>On Mon, Jul 13, 2015 at 02:49:38PM +0200, Dirk Behme wrote:
> >>>>From: Oleksij Rempel <external.Oleksij.Rempel@de.bosch.com>
> >>>>
> >>>>If zforce is not ready to process the interrupt, the touchscreen will
> >>>>be lost forever. Make sure we enable the interrupt only if processing
> >>>>is ready.
> >>>>
> >>>>Signed-off-by: Oleksij Rempel <external.Oleksij.Rempel@de.bosch.com>
> >>>>Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com>
> >>>>---
> >>>>  drivers/input/touchscreen/zforce_ts.c | 7 ++++++-
> >>>>  1 file changed, 6 insertions(+), 1 deletion(-)
> >>>>
> >>>>diff --git a/drivers/input/touchscreen/zforce_ts.c b/drivers/input/touchscreen/zforce_ts.c
> >>>>index 19dc297..a1889e5 100644
> >>>>--- a/drivers/input/touchscreen/zforce_ts.c
> >>>>+++ b/drivers/input/touchscreen/zforce_ts.c
> >>>>@@ -22,6 +22,7 @@
> >>>>  #include <linux/slab.h>
> >>>>  #include <linux/input.h>
> >>>>  #include <linux/interrupt.h>
> >>>>+#include <linux/irq.h>
> >>>>  #include <linux/i2c.h>
> >>>>  #include <linux/delay.h>
> >>>>  #include <linux/gpio/consumer.h>
> >>>>@@ -741,6 +742,7 @@ static int zforce_probe(struct i2c_client *client,
> >>>>  	struct zforce_ts *ts;
> >>>>  	struct input_dev *input_dev;
> >>>>  	int ret;
> >>>>+	unsigned int irq;
> >>>>  	if (!pdata) {
> >>>>  		pdata = zforce_parse_dt(&client->dev);
> >>>>@@ -835,6 +837,7 @@ static int zforce_probe(struct i2c_client *client,
> >>>>  	init_completion(&ts->command_done);
> >>>>+	irq = client->irq;
> >>>>  	/*
> >>>>  	 * The zforce pulls the interrupt low when it has data ready.
> >>>>  	 * After it is triggered the isr thread runs until all the available
> >>>>@@ -842,7 +845,8 @@ static int zforce_probe(struct i2c_client *client,
> >>>>  	 * Therefore we can trigger the interrupt anytime it is low and do
> >>>>  	 * not need to limit it to the interrupt edge.
> >>>>  	 */
> >>>>-	ret = devm_request_threaded_irq(&client->dev, client->irq,
> >>>>+	irq_set_status_flags(irq, IRQ_NOAUTOEN);
> >>>Instead of playing with the flags should we simply request irq after we
> >>>release the reset pin?
> >>Because we should be able to process the interrupt. If i put
> >>request_irq after reset, some times the interrupt can be missed.
> >OK, I see that enabling after reset is racy. But I am still confused why
> >having IRQ enabled while reste pin is asserted results in lost
> >touchscreen. Can you walk me through the sequence of events?
> >
> >Thanks.
> Mostly it will fail if zforce attached over SerDes
> (Serializer/Deserializer). If we register IRQ after release of reset
> pin, SerDes will get irq just before it has irq handler. In this
> case irq will be lost, which means, not BOOT event will be passed to
> the zforce.

Yes, I agreed that requesting interrupt after releasing reset pin is not
a good idea. But what is the issue with the original code that requests
interrupt first (and enables it) and then releases the reset pin?

Thanks.

-- 
Dmitry