linux-kernel - [PATCH v2] driver core: Extend returning EPROBE_DEFER for two minutes after late

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Date:   Fri, 14 Feb 2020 23:32:26 +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>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-pm@...r.kernel.org
Subject: [PATCH v2] driver core: Extend returning EPROBE_DEFER for two minutes after late_initcall

Due to commit e01afc3250255 ("PM / Domains: Stop deferring probe
at the end of initcall"), along with commit 25b4e70dcce9
("driver core: allow stopping deferred probe after init") after
late_initcall, drivers will stop getting EPROBE_DEFER, and
instead see an error causing the driver to fail to load.

That change causes trouble when trying to use many clk drivers
as modules, as the clk modules may not load until much later
after init has started. If a dependent driver loads and gets an
error instead of EPROBE_DEFER, it won't try to reload later when
the dependency is met, and will thus fail to load.

Instead of reverting that patch, this patch tries to extend the
time that EPROBE_DEFER is retruned by 30 seconds, to (hopefully)
ensure that everything has had a chance to load.

30 seconds was chosen to match the similar timeout used by the
regulator code here in commit 55576cf18537 ("regulator: Defer
init completion for a while after late_initcall")

Specifically, on db845c, this change allows us to set
SDM_GPUCC_845, QCOM_CLK_RPMH and COMMON_CLK_QCOM as modules and
get a working system, where as without it the display will fail
to load.

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: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-pm@...r.kernel.org
Fixes: e01afc3250255 ("PM / Domains: Stop deferring probe at the end of initcall")
Fixes: 25b4e70dcce9 ("driver core: allow stopping deferred probe after init")
Signed-off-by: John Stultz <john.stultz@...aro.org>
---
v2:
* Add calls to driver_deferred_probe_trigger() after the two minute timeout,
  as suggested by Bjorn
* Minor whitespace cleanups
* Switch to 30 second timeout to match what the regulator code is doing as
  suggested by Rob.
---
 drivers/base/dd.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index d811e60610d3..0f519ef3b257 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -311,6 +311,15 @@ static void deferred_probe_timeout_work_func(struct work_struct *work)
 }
 static DECLARE_DELAYED_WORK(deferred_probe_timeout_work, deferred_probe_timeout_work_func);
 
+static void deferred_initcall_done_work_func(struct work_struct *work)
+{
+	initcalls_done = true;
+	driver_deferred_probe_trigger();
+	flush_work(&deferred_probe_work);
+}
+static DECLARE_DELAYED_WORK(deferred_initcall_done_work,
+			    deferred_initcall_done_work_func);
+
 /**
  * deferred_probe_initcall() - Enable probing of deferred devices
  *
@@ -327,7 +336,8 @@ static int deferred_probe_initcall(void)
 	driver_deferred_probe_trigger();
 	/* Sort as many dependencies as possible before exiting initcalls */
 	flush_work(&deferred_probe_work);
-	initcalls_done = true;
+	schedule_delayed_work(&deferred_initcall_done_work,
+			      msecs_to_jiffies(30000));
 
 	/*
 	 * Trigger deferred probe again, this time we won't defer anything
-- 
2.17.1