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From: Matthias Kaehlcke <mka@chromium.org>
To: MyungJoo Ham <myungjoo.ham@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>,
	Chanwoo Choi <cw00.choi@samsung.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	linux-pm@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Brian Norris <briannorris@chromium.org>,
	Douglas Anderson <dianders@chromium.org>,
	Enric Balletbo i Serra <enric.balletbo@collabora.com>,
	Matthias Kaehlcke <mka@chromium.org>
Subject: [PATCH v2 02/11] PM / devfreq: Fix handling of min/max_freq == 0
Date: Thu,  7 Jun 2018 11:12:05 -0700	[thread overview]
Message-ID: <20180607181214.30338-3-mka@chromium.org> (raw)
In-Reply-To: <20180607181214.30338-1-mka@chromium.org>

Commit ab8f58ad72c4 ("PM / devfreq: Set min/max_freq when adding the
devfreq device") initializes df->min/max_freq with the min/max OPP when
the device is added. Later commit f1d981eaecf8 ("PM / devfreq: Use the
available min/max frequency") adds df->scaling_min/max_freq and the
following to the frequency adjustment code:

  max_freq = MIN(devfreq->scaling_max_freq, devfreq->max_freq);

With the current handling of min/max_freq this is incorrect:

Even though df->max_freq is now initialized to a value != 0 user space
can still set it to 0, in this case max_freq would be 0 instead of
df->scaling_max_freq as intended. In consequence the frequency adjustment
is not performed:

  if (max_freq && freq > max_freq) {
	freq = max_freq;

To fix this set df->min/max freq to the min/max OPP in max/max_freq_store,
when the user passes a value of 0. This also prevents df->max_freq from
being set below the min OPP when df->min_freq is 0, and similar for
min_freq. Since it is now guaranteed that df->min/max_freq can't be 0 the
checks for this case can be removed.

Fixes: f1d981eaecf8 ("PM / devfreq: Use the available min/max frequency")
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
---
Changes in v2:
- handle freq tables sorted in ascending and descending order in
  min/max_freq_store()
- use same order for conditional statements in min/max_freq_store()

 drivers/devfreq/devfreq.c | 42 ++++++++++++++++++++++++++++-----------
 1 file changed, 30 insertions(+), 12 deletions(-)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 0057ef5b0a98..6f604f8b2b81 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -283,11 +283,11 @@ int update_devfreq(struct devfreq *devfreq)
 	max_freq = MIN(devfreq->scaling_max_freq, devfreq->max_freq);
 	min_freq = MAX(devfreq->scaling_min_freq, devfreq->min_freq);
 
-	if (min_freq && freq < min_freq) {
+	if (freq < min_freq) {
 		freq = min_freq;
 		flags &= ~DEVFREQ_FLAG_LEAST_UPPER_BOUND; /* Use GLB */
 	}
-	if (max_freq && freq > max_freq) {
+	if (freq > max_freq) {
 		freq = max_freq;
 		flags |= DEVFREQ_FLAG_LEAST_UPPER_BOUND; /* Use LUB */
 	}
@@ -1122,18 +1122,27 @@ static ssize_t min_freq_store(struct device *dev, struct device_attribute *attr,
 {
 	struct devfreq *df = to_devfreq(dev);
 	unsigned long value;
+	unsigned long *freq_table;
 	int ret;
-	unsigned long max;
 
 	ret = sscanf(buf, "%lu", &value);
 	if (ret != 1)
 		return -EINVAL;
 
 	mutex_lock(&df->lock);
-	max = df->max_freq;
-	if (value && max && value > max) {
-		ret = -EINVAL;
-		goto unlock;
+
+	if (value) {
+		if (value > df->max_freq) {
+			ret = -EINVAL;
+			goto unlock;
+		}
+	} else {
+		freq_table = df->profile->freq_table;
+		/* typical order is ascending, some drivers use descending */
+		if (freq_table[0] < freq_table[df->profile->max_state - 1])
+			value = freq_table[0];
+		else
+			value = freq_table[df->profile->max_state - 1];
 	}
 
 	df->min_freq = value;
@@ -1157,18 +1166,27 @@ static ssize_t max_freq_store(struct device *dev, struct device_attribute *attr,
 {
 	struct devfreq *df = to_devfreq(dev);
 	unsigned long value;
+	unsigned long *freq_table;
 	int ret;
-	unsigned long min;
 
 	ret = sscanf(buf, "%lu", &value);
 	if (ret != 1)
 		return -EINVAL;
 
 	mutex_lock(&df->lock);
-	min = df->min_freq;
-	if (value && min && value < min) {
-		ret = -EINVAL;
-		goto unlock;
+
+	if (value) {
+		if (value < df->min_freq) {
+			ret = -EINVAL;
+			goto unlock;
+		}
+	} else {
+		freq_table = df->profile->freq_table;
+		/* typical order is ascending, some drivers use descending */
+		if (freq_table[0] < freq_table[df->profile->max_state - 1])
+			value = freq_table[df->profile->max_state - 1];
+		else
+			value = freq_table[0];
 	}
 
 	df->max_freq = value;
-- 
2.18.0.rc1.242.g61856ae69a-goog

  parent reply	other threads:[~2018-06-07 18:13 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-07 18:12 [PATCH v2 00/11] Add throttler driver for non-thermal throttling Matthias Kaehlcke
2018-06-07 18:12 ` [PATCH v2 01/11] PM / devfreq: Init user limits from OPP limits, not viceversa Matthias Kaehlcke
2018-06-07 18:12 ` Matthias Kaehlcke [this message]
2018-06-07 18:12 ` [PATCH v2 03/11] PM / devfreq: Don't adjust to user limits in governors Matthias Kaehlcke
2018-06-07 18:12 ` [PATCH v2 04/11] PM / devfreq: Add struct devfreq_policy Matthias Kaehlcke
2018-06-07 18:12 ` [PATCH v2 05/11] PM / devfreg: Add support for policy notifiers Matthias Kaehlcke
2018-06-08 23:21   ` kbuild test robot
2018-06-09  1:16   ` kbuild test robot
2018-06-07 18:12 ` [PATCH v2 06/11] PM / devfreq: Make update_devfreq() public Matthias Kaehlcke
2018-06-07 18:12 ` [PATCH v2 07/11] PM / devfreq: export devfreq_class Matthias Kaehlcke
2018-06-07 18:12 ` [PATCH v2 08/11] dt-bindings: PM / OPP: add opp-throttlers property Matthias Kaehlcke
2018-06-07 18:12 ` [PATCH v2 09/11] misc: throttler: Add core support for non-thermal throttling Matthias Kaehlcke
2018-06-09  4:34   ` kbuild test robot
2018-06-12  1:49   ` Brian Norris
2018-06-12 17:11     ` Matthias Kaehlcke
2018-06-12 20:00       ` Brian Norris
2018-06-13  1:48         ` Matthias Kaehlcke
2018-06-07 18:12 ` [PATCH v2 10/11] dt-bindings: misc: add bindings for cros_ec_throttler Matthias Kaehlcke
2018-06-12 19:10   ` Rob Herring
2018-06-12 20:40     ` Brian Norris
2018-06-13  2:00       ` Matthias Kaehlcke
2018-06-07 18:12 ` [PATCH v2 11/11] misc: throttler: Add Chrome OS EC throttler Matthias Kaehlcke
2018-06-08 14:09   ` Enric Balletbo i Serra
2018-06-08 15:56     ` Matthias Kaehlcke
2018-06-28 18:52 ` [PATCH v2 00/11] Add throttler driver for non-thermal throttling Pavel Machek

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