iio: accel: try to fix problems with the sc7a20 accelerometer after

resume

Previously, when resuming from sleep, the PineNote would emit the
following stack trace caused by some kind of mishandling of the irq of
the accelerometer

pinenote kernel: irq 79: nobody cared (try booting with the "irqpoll" option)
pinenote kernel: CPU: 0 PID: 310 Comm: irq/79-sc7a20-t Not tainted 5.17.0-rc6-next-20220304-pinenote-202307051629 #1
pinenote kernel: Hardware name: Pine64 PineNote v1.2 (DT)
pinenote kernel: Call trace:
pinenote kernel:  dump_backtrace.part.0+0xc4/0xd0
pinenote kernel:  show_stack+0x14/0x60
pinenote kernel:  dump_stack_lvl+0x60/0x78
pinenote kernel:  dump_stack+0x14/0x2c
pinenote kernel:  __report_bad_irq+0x48/0x158
pinenote kernel:  note_interrupt+0x2f4/0x3f0
pinenote kernel:  handle_irq_event+0xd4/0x160
pinenote kernel:  handle_level_irq+0xd4/0x200
pinenote kernel:  generic_handle_irq+0x2c/0x40
pinenote kernel:  rockchip_irq_demux+0xa4/0x224
pinenote kernel:  generic_handle_domain_irq+0x38/0x5c
pinenote kernel:  gic_handle_irq+0xac/0x124
pinenote kernel:  call_on_irq_stack+0x2c/0x38
pinenote kernel:  do_interrupt_handler+0x78/0x84
pinenote kernel:  el1_interrupt+0x30/0x50
pinenote kernel:  el1h_64_irq_handler+0x14/0x20
pinenote kernel:  el1h_64_irq+0x64/0x68
pinenote kernel:  irq_finalize_oneshot.part.0+0x94/0x160
pinenote kernel:  irq_thread_fn+0x5c/0x90
pinenote kernel:  irq_thread+0x170/0x21c
pinenote kernel:  kthread+0xd4/0xdc
pinenote kernel:  ret_from_fork+0x10/0x20
pinenote kernel: handlers:
pinenote kernel: [<00000000117b7317>] st_sensors_irq_handler [st_sensors] threaded [<00000000e2a480c4>] st_sensors_irq_thread [st_sensors]
pinenote kernel: Disabling IRQ torvalds#79

It seems that the irq handler was triggered after the actual irq was
already disabled for sleep by the system, leading to the irq handler not
actually handling those irqs. I may be wrong with that interpretation...

Sometimes this lead to the accelerometer not working after resume.

In order to prevent spurious irqs during the standby/resume cycle,
explicitly turn off the device and irq during suspend, and resume by
hand when the system resumes.

Signed-off-by: Maximilian Weigand <mweigand@mweigand.net>

drivers/iio/accel/st_accel_i2c.c

@@ -202,11 +202,51 @@ static int st_accel_i2c_probe(struct i2c_client *client)
 	return st_accel_common_probe(indio_dev);
 }
 
+static int __maybe_unused st_accel_suspend(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct iio_dev *indio_dev;
+	int ret;
+	struct st_sensor_data *sdata;
+
+	indio_dev = i2c_get_clientdata(client);
+	sdata = iio_priv(indio_dev);
+	pr_info("%s", __func__);
+	st_sensors_set_enable(indio_dev, false);
+	st_sensors_set_dataready_irq(indio_dev, false);
+	disable_irq(sdata->irq);
+
+	return 0;
+}
+
+static int __maybe_unused st_accel_resume(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct iio_dev *indio_dev;
+	struct st_sensor_data *sdata;
+	int ret;
+
+	indio_dev = i2c_get_clientdata(client);
+	sdata = iio_priv(indio_dev);
+
+	pr_info("%s", __func__);
+	st_sensors_set_enable(indio_dev, true);
+	st_sensors_set_dataready_irq(indio_dev, true);
+	// enabling the irq here will reduce the number of spurious irqs, and the
+	// device will keep on working after resume.
+	// Still not enough...
+	enable_irq(sdata->irq);
+	return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(st_accel_pm, st_accel_suspend, st_accel_resume);
+
 static struct i2c_driver st_accel_driver = {
 	.driver = {
 		.name = "st-accel-i2c",
 		.of_match_table = st_accel_of_match,
 		.acpi_match_table = st_accel_acpi_match,
+		.pm		= &st_accel_pm,
 	},
 	.probe = st_accel_i2c_probe,
 	.id_table = st_accel_id_table,

drivers/iio/common/st_sensors/st_sensors_trigger.c

@@ -87,6 +87,16 @@ static irqreturn_t st_sensors_irq_thread(int irq, void *p)
 	    st_sensors_new_samples_available(indio_dev, sdata)) {
 		iio_trigger_poll_nested(p);
 	} else {
+		pr_info(
+			"st_sensors_irq_thread: %i returning IRQ_NONE (%i/%i/%i/%u) %s",
+			irq,
+		   	sdata->hw_irq_trigger,
+			st_sensors_new_samples_available(indio_dev, sdata),
+			sdata->num_data_channels,
+			sdata->odr,
+			trig->name
+		);
+		/* return IRQ_HANDLED; */
 		dev_dbg(indio_dev->dev.parent, "spurious IRQ\n");
 		return IRQ_NONE;
 	}