linux-kernel - [PATCH 6/7] regulator: core: Avoid propagating to supplies when possible

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20181120002654.1891-6-dianders@chromium.org>
Date:   Mon, 19 Nov 2018 16:26:53 -0800
From:   Douglas Anderson <dianders@...omium.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     Bjorn Andersson <bjorn.andersson@...aro.org>, evgreen@...omium.org,
        swboyd@...omium.org, Dmitry Osipenko <digetx@...il.com>,
        ryandcase@...omium.org, David Collins <collinsd@...eaurora.org>,
        linux-arm-msm@...r.kernel.org,
        Douglas Anderson <dianders@...omium.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 6/7] regulator: core: Avoid propagating to supplies when possible

When we called regulator_enable() on a regulator we'd end up
propagating that call all the way up the chain every time.  This is a
bit of a waste of time.  A child regulator already refcounts its own
enables so it should avoid passing on to its parent unless the
refcount transitioned between 0 and 1.

Historically this hasn't been a huge problem since we skipped dealing
with enable for always-on regulators.  In a previous patch, however,
we removed the always-on optimization.  On one system, the debugfs
regulator_summary was now showing a "use_count" of 33 for a top-level
regulator.

Let's implement this optimization.  This turns out to be fairly
trivial with the recent reorganization of the regulator core.

NOTE: as part of this patch I'll make "always-on" regulators start
with a use count of 1.  This keeps the counts clean when recursively
resolving regulators.

Signed-off-by: Douglas Anderson <dianders@...omium.org>
---

 drivers/regulator/core.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 23e852d38b88..2eda87520832 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -1822,6 +1822,7 @@ static int regulator_resolve_supply(struct regulator_dev *rdev)
 			rdev->supply = NULL;
 			return ret;
 		}
+		rdev->use_count = 1;
 	}
 
 	return 0;
@@ -2491,7 +2492,7 @@ static int _regulator_enable(struct regulator *regulator)
 
 	lockdep_assert_held_once(&rdev->mutex.base);
 
-	if (rdev->supply) {
+	if (rdev->use_count == 0 && rdev->supply) {
 		ret = _regulator_enable(rdev->supply);
 		if (ret < 0)
 			return ret;
@@ -2539,7 +2540,7 @@ static int _regulator_enable(struct regulator *regulator)
 	_regulator_handle_consumer_disable(regulator);
 
 err_disable_supply:
-	if (rdev->supply)
+	if (rdev->use_count == 0 && rdev->supply)
 		_regulator_disable(rdev->supply);
 
 	return ret;
@@ -2648,7 +2649,7 @@ static int _regulator_disable(struct regulator *regulator)
 	if (ret == 0 && rdev->coupling_desc.n_coupled > 1)
 		ret = regulator_balance_voltage(rdev, PM_SUSPEND_ON);
 
-	if (ret == 0 && rdev->supply)
+	if (ret == 0 && rdev->use_count == 0 && rdev->supply)
 		ret = _regulator_disable(rdev->supply);
 
 	return ret;
-- 
2.19.1.1215.g8438c0b245-goog