linux-kernel - [PATCH v3 2/2] driver core: Make deferred_probe

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Date:   Tue, 18 Feb 2020 22:07:48 +0000
From:   John Stultz <john.stultz@...aro.org>
To:     lkml <linux-kernel@...r.kernel.org>
Cc:     John Stultz <john.stultz@...aro.org>,
        Rob Herring <robh@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
        Todd Kjos <tkjos@...gle.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-pm@...r.kernel.org
Subject: [PATCH v3 2/2] driver core: Make deferred_probe_timeout global so it can be shared

This patch, suggested by Rob, allows deferred_probe_timeout to
be global so other substems can use it.

This also sets the default to 30 instead of -1 (no timeout) and
modifies the regulator code to make use of it instead of its
hard-coded 30 second interval.

In the case that deferred_probe_timeout is manually set to -1,
we preserve the regulator's hard coded 30 second interval (just
to be cautious this doesn't change behavior in that case).

Feedback would be apprecaited!

Cc: Rob Herring <robh@...nel.org>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: Kevin Hilman <khilman@...nel.org>
Cc: Ulf Hansson <ulf.hansson@...aro.org>
Cc: Pavel Machek <pavel@....cz>
Cc: Len Brown <len.brown@...el.com>
Cc: Todd Kjos <tkjos@...gle.com>
Cc: Bjorn Andersson <bjorn.andersson@...aro.org>
Cc: Liam Girdwood <lgirdwood@...il.com>
Cc: Mark Brown <broonie@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-pm@...r.kernel.org
Signed-off-by: John Stultz <john.stultz@...aro.org>
---
 drivers/base/dd.c             |  4 +++-
 drivers/regulator/core.c      | 12 ++++++++----
 include/linux/device/driver.h |  1 +
 3 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 9d916a7b56a6..c8e025a20a9d 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -224,7 +224,9 @@ static int deferred_devs_show(struct seq_file *s, void *data)
 }
 DEFINE_SHOW_ATTRIBUTE(deferred_devs);
 
-static int deferred_probe_timeout = -1;
+int deferred_probe_timeout = 30;
+EXPORT_SYMBOL_GPL(deferred_probe_timeout);
+
 static int __init deferred_probe_timeout_setup(char *str)
 {
 	int timeout;
diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index d015d99cb59d..889d08e65f19 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -5757,6 +5757,11 @@ static DECLARE_DELAYED_WORK(regulator_init_complete_work,
 
 static int __init regulator_init_complete(void)
 {
+	int delay = deferred_probe_timeout;
+
+	/* preserve 30 second interval if deferred_probe_timeout=-1 */
+	if (delay < 0)
+		delay = 30;
 	/*
 	 * Since DT doesn't provide an idiomatic mechanism for
 	 * enabling full constraints and since it's much more natural
@@ -5767,18 +5772,17 @@ static int __init regulator_init_complete(void)
 		has_full_constraints = true;
 
 	/*
-	 * We punt completion for an arbitrary amount of time since
+	 * We punt completion for deferred_probe_timeout seconds since
 	 * systems like distros will load many drivers from userspace
 	 * so consumers might not always be ready yet, this is
 	 * particularly an issue with laptops where this might bounce
 	 * the display off then on.  Ideally we'd get a notification
 	 * from userspace when this happens but we don't so just wait
 	 * a bit and hope we waited long enough.  It'd be better if
-	 * we'd only do this on systems that need it, and a kernel
-	 * command line option might be useful.
+	 * we'd only do this on systems that need it.
 	 */
 	schedule_delayed_work(&regulator_init_complete_work,
-			      msecs_to_jiffies(30000));
+			      delay * HZ);
 
 	return 0;
 }
diff --git a/include/linux/device/driver.h b/include/linux/device/driver.h
index 1188260f9a02..b3ff8cb3fbd6 100644
--- a/include/linux/device/driver.h
+++ b/include/linux/device/driver.h
@@ -236,6 +236,7 @@ driver_find_device_by_acpi_dev(struct device_driver *drv, const void *adev)
 }
 #endif
 
+extern int deferred_probe_timeout;
 void driver_deferred_probe_add(struct device *dev);
 int driver_deferred_probe_check_state(struct device *dev);
 int driver_deferred_probe_check_state_continue(struct device *dev);
-- 
2.17.1