linux-kernel - [RFC PATCH 3/3] iio: kx022a: Probe asynchronously

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Message-ID: <24cea76c282a28b7a4dba297ab627176f8097907.1683185765.git.mazziesaccount@gmail.com>
Date:   Thu, 4 May 2023 10:58:52 +0300
From:   Matti Vaittinen <mazziesaccount@...il.com>
To:     Matti Vaittinen <mazziesaccount@...il.com>,
        Matti Vaittinen <matti.vaittinen@...rohmeurope.com>
Cc:     Matti Vaittinen <mazziesaccount@...il.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH 3/3] iio: kx022a: Probe asynchronously

Devices which may take a while to initialize during probe and which have
no strong reason to probe synchronously can request asynchronous probing
as default probe strategy. This can speed-up start times on some
platforms.

The KX022A gets probe delayed for at least two reasons. It enables the
supply regulator, (which is likely to have ramp-up delay if it was
disabled) and additionally it delays while the sensor itself is
initializing.

Changing to asynchronous probing may cause problems. Some of which are
discussed in:
https://lore.kernel.org/all/06db017f-e985-4434-8d1d-02ca2100cca0@sirena.org.uk/

Enable asynchronous probing for KX022A.

Signed-off-by: Matti Vaittinen <mazziesaccount@...il.com>

---

I am unsure if this change is 100% safe - but I don't immediately see
the harm. Please let me know if some of you have more experience on
problems when using asynchronous probing with IIO devices.
---
 drivers/iio/accel/kionix-kx022a-i2c.c | 1 +
 drivers/iio/accel/kionix-kx022a-spi.c | 1 +
 2 files changed, 2 insertions(+)

diff --git a/drivers/iio/accel/kionix-kx022a-i2c.c b/drivers/iio/accel/kionix-kx022a-i2c.c
index e6fd02d931b6..ee982206e5dd 100644
--- a/drivers/iio/accel/kionix-kx022a-i2c.c
+++ b/drivers/iio/accel/kionix-kx022a-i2c.c
@@ -40,6 +40,7 @@ static struct i2c_driver kx022a_i2c_driver = {
 	.driver = {
 		.name  = "kx022a-i2c",
 		.of_match_table = kx022a_of_match,
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
 	  },
 	.probe_new    = kx022a_i2c_probe,
 };
diff --git a/drivers/iio/accel/kionix-kx022a-spi.c b/drivers/iio/accel/kionix-kx022a-spi.c
index 9cd047f7b346..f45a46899a5f 100644
--- a/drivers/iio/accel/kionix-kx022a-spi.c
+++ b/drivers/iio/accel/kionix-kx022a-spi.c
@@ -46,6 +46,7 @@ static struct spi_driver kx022a_spi_driver = {
 	.driver = {
 		.name   = "kx022a-spi",
 		.of_match_table = kx022a_of_match,
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
 	},
 	.probe = kx022a_spi_probe,
 	.id_table = kx022a_id,
-- 
2.40.0


-- 
Matti Vaittinen, Linux device drivers
ROHM Semiconductors, Finland SWDC
Kiviharjunlenkki 1E
90220 OULU
FINLAND

~~~ "I don't think so," said Rene Descartes. Just then he vanished ~~~
Simon says - in Latin please.
~~~ "non cogito me" dixit Rene Descarte, deinde evanescavit ~~~
Thanks to Simon Glass for the translation =] 

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