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Date: Fri, 18 Jan 2013 13:52:35 -0600
From: Nishanth Menon <nm@...com>
To: linux-pm <linux-pm@...r.kernel.org>
CC: Rafael <rjw@...k.pl>, Kevin <khilman@...prootsystems.com>,
MyungJoo Ham <myungjoo.ham@...sung.com>,
lkml <linux-kernel@...r.kernel.org>,
lo <linux-omap@...r.kernel.org>, Jack <jack@...ed.me.uk>,
Alexander <holler@...oftware.de>, Nishanth Menon <nm@...com>
Subject: [PATCH 4/4] PM / devfreq: exynos4_bus: honor RCU lock usage
OPP pointers cannot be expected to be valid beyond the boundary
of rcu_read_lock and rcu_read_unlock. Unfortunately, the current
exynos4 busfreq driver does not honor the usage constraint and stores
the OPP pointer in struct busfreq_data. This could potentially
become invalid later such as: across devfreq opp change decisions,
resulting in unpredictable behavior.
To fix this, we introduce a busfreq specific busfreq_opp_info
structure which is used to handle OPP information. OPP information
is de-referenced to voltage and frequency pairs as needed into
busfreq_opp_info structure and used as needed.
Signed-off-by: Nishanth Menon <nm@...com>
---
drivers/devfreq/exynos4_bus.c | 94 +++++++++++++++++++++++++++++------------
1 file changed, 67 insertions(+), 27 deletions(-)
diff --git a/drivers/devfreq/exynos4_bus.c b/drivers/devfreq/exynos4_bus.c
index 80c745e..6d72f12 100644
--- a/drivers/devfreq/exynos4_bus.c
+++ b/drivers/devfreq/exynos4_bus.c
@@ -73,6 +73,16 @@ enum busclk_level_idx {
#define EX4210_LV_NUM (LV_2 + 1)
#define EX4x12_LV_NUM (LV_4 + 1)
+/**
+ * struct busfreq_opp_info - opp information for bus
+ * @rate: Frequency in hertz
+ * @volt: Voltage in microvolts corresponding to this OPP
+ */
+struct busfreq_opp_info {
+ unsigned long rate;
+ unsigned long volt;
+};
+
struct busfreq_data {
enum exynos4_busf_type type;
struct device *dev;
@@ -80,7 +90,7 @@ struct busfreq_data {
bool disabled;
struct regulator *vdd_int;
struct regulator *vdd_mif; /* Exynos4412/4212 only */
- struct opp *curr_opp;
+ struct busfreq_opp_info curr_oppinfo;
struct exynos4_ppmu dmc[2];
struct notifier_block pm_notifier;
@@ -296,13 +306,14 @@ static unsigned int exynos4x12_clkdiv_sclkip[][3] = {
};
-static int exynos4210_set_busclk(struct busfreq_data *data, struct opp *opp)
+static int exynos4210_set_busclk(struct busfreq_data *data,
+ struct busfreq_opp_info *oppi)
{
unsigned int index;
unsigned int tmp;
for (index = LV_0; index < EX4210_LV_NUM; index++)
- if (opp_get_freq(opp) == exynos4210_busclk_table[index].clk)
+ if (oppi->rate == exynos4210_busclk_table[index].clk)
break;
if (index == EX4210_LV_NUM)
@@ -361,13 +372,14 @@ static int exynos4210_set_busclk(struct busfreq_data *data, struct opp *opp)
return 0;
}
-static int exynos4x12_set_busclk(struct busfreq_data *data, struct opp *opp)
+static int exynos4x12_set_busclk(struct busfreq_data *data,
+ struct busfreq_opp_info *oppi)
{
unsigned int index;
unsigned int tmp;
for (index = LV_0; index < EX4x12_LV_NUM; index++)
- if (opp_get_freq(opp) == exynos4x12_mifclk_table[index].clk)
+ if (oppi->rate == exynos4x12_mifclk_table[index].clk)
break;
if (index == EX4x12_LV_NUM)
@@ -576,11 +588,12 @@ static int exynos4x12_get_intspec(unsigned long mifclk)
return -EINVAL;
}
-static int exynos4_bus_setvolt(struct busfreq_data *data, struct opp *opp,
- struct opp *oldopp)
+static int exynos4_bus_setvolt(struct busfreq_data *data,
+ struct busfreq_opp_info *oppi,
+ struct busfreq_opp_info *oldoppi)
{
int err = 0, tmp;
- unsigned long volt = opp_get_voltage(opp);
+ unsigned long volt = oppi->volt;
switch (data->type) {
case TYPE_BUSF_EXYNOS4210:
@@ -595,11 +608,11 @@ static int exynos4_bus_setvolt(struct busfreq_data *data, struct opp *opp,
if (err)
break;
- tmp = exynos4x12_get_intspec(opp_get_freq(opp));
+ tmp = exynos4x12_get_intspec(oppi->rate);
if (tmp < 0) {
err = tmp;
regulator_set_voltage(data->vdd_mif,
- opp_get_voltage(oldopp),
+ oldoppi->volt,
MAX_SAFEVOLT);
break;
}
@@ -609,7 +622,7 @@ static int exynos4_bus_setvolt(struct busfreq_data *data, struct opp *opp,
/* Try to recover */
if (err)
regulator_set_voltage(data->vdd_mif,
- opp_get_voltage(oldopp),
+ oldoppi->volt,
MAX_SAFEVOLT);
break;
default:
@@ -626,17 +639,26 @@ static int exynos4_bus_target(struct device *dev, unsigned long *_freq,
struct platform_device *pdev = container_of(dev, struct platform_device,
dev);
struct busfreq_data *data = platform_get_drvdata(pdev);
- struct opp *opp = devfreq_recommended_opp(dev, _freq, flags);
- unsigned long freq = opp_get_freq(opp);
- unsigned long old_freq = opp_get_freq(data->curr_opp);
+ struct opp *opp;
+ unsigned long freq;
+ unsigned long old_freq = data->curr_oppinfo.rate;
+ struct busfreq_opp_info new_oppinfo;
- if (IS_ERR(opp))
+ rcu_read_lock();
+ opp = devfreq_recommended_opp(dev, _freq, flags);
+ if (IS_ERR(opp)) {
+ rcu_read_unlock();
return PTR_ERR(opp);
+ }
+ new_oppinfo.rate = opp_get_freq(opp);
+ new_oppinfo.volt = opp_get_voltage(opp);
+ rcu_read_unlock();
+ freq = new_oppinfo.rate;
if (old_freq == freq)
return 0;
- dev_dbg(dev, "targetting %lukHz %luuV\n", freq, opp_get_voltage(opp));
+ dev_dbg(dev, "targetting %lukHz %luuV\n", freq, new_oppinfo.volt);
mutex_lock(&data->lock);
@@ -644,17 +666,18 @@ static int exynos4_bus_target(struct device *dev, unsigned long *_freq,
goto out;
if (old_freq < freq)
- err = exynos4_bus_setvolt(data, opp, data->curr_opp);
+ err = exynos4_bus_setvolt(data, &new_oppinfo,
+ &data->curr_oppinfo);
if (err)
goto out;
if (old_freq != freq) {
switch (data->type) {
case TYPE_BUSF_EXYNOS4210:
- err = exynos4210_set_busclk(data, opp);
+ err = exynos4210_set_busclk(data, &new_oppinfo);
break;
case TYPE_BUSF_EXYNOS4x12:
- err = exynos4x12_set_busclk(data, opp);
+ err = exynos4x12_set_busclk(data, &new_oppinfo);
break;
default:
err = -EINVAL;
@@ -664,11 +687,12 @@ static int exynos4_bus_target(struct device *dev, unsigned long *_freq,
goto out;
if (old_freq > freq)
- err = exynos4_bus_setvolt(data, opp, data->curr_opp);
+ err = exynos4_bus_setvolt(data, &new_oppinfo,
+ &data->curr_oppinfo);
if (err)
goto out;
- data->curr_opp = opp;
+ data->curr_oppinfo = new_oppinfo;
out:
mutex_unlock(&data->lock);
return err;
@@ -702,7 +726,7 @@ static int exynos4_bus_get_dev_status(struct device *dev,
exynos4_read_ppmu(data);
busier_dmc = exynos4_get_busier_dmc(data);
- stat->current_frequency = opp_get_freq(data->curr_opp);
+ stat->current_frequency = data->curr_oppinfo.rate;
if (busier_dmc)
addr = S5P_VA_DMC1;
@@ -933,6 +957,7 @@ static int exynos4_busfreq_pm_notifier_event(struct notifier_block *this,
struct busfreq_data *data = container_of(this, struct busfreq_data,
pm_notifier);
struct opp *opp;
+ struct busfreq_opp_info new_oppinfo;
unsigned long maxfreq = ULONG_MAX;
int err = 0;
@@ -943,18 +968,29 @@ static int exynos4_busfreq_pm_notifier_event(struct notifier_block *this,
data->disabled = true;
+ rcu_read_lock();
opp = opp_find_freq_floor(data->dev, &maxfreq);
+ if (IS_ERR(opp)) {
+ rcu_read_unlock();
+ dev_err(data->dev, "%s: unable to find a min freq\n",
+ __func__);
+ return PTR_ERR(opp);
+ }
+ new_oppinfo.rate = opp_get_freq(opp);
+ new_oppinfo.volt = opp_get_voltage(opp);
+ rcu_read_unlock();
- err = exynos4_bus_setvolt(data, opp, data->curr_opp);
+ err = exynos4_bus_setvolt(data, &new_oppinfo,
+ &data->curr_oppinfo);
if (err)
goto unlock;
switch (data->type) {
case TYPE_BUSF_EXYNOS4210:
- err = exynos4210_set_busclk(data, opp);
+ err = exynos4210_set_busclk(data, &new_oppinfo);
break;
case TYPE_BUSF_EXYNOS4x12:
- err = exynos4x12_set_busclk(data, opp);
+ err = exynos4x12_set_busclk(data, &new_oppinfo);
break;
default:
err = -EINVAL;
@@ -962,7 +998,7 @@ static int exynos4_busfreq_pm_notifier_event(struct notifier_block *this,
if (err)
goto unlock;
- data->curr_opp = opp;
+ data->curr_oppinfo = new_oppinfo;
unlock:
mutex_unlock(&data->lock);
if (err)
@@ -1027,13 +1063,17 @@ static int exynos4_busfreq_probe(struct platform_device *pdev)
}
}
+ rcu_read_lock();
opp = opp_find_freq_floor(dev, &exynos4_devfreq_profile.initial_freq);
if (IS_ERR(opp)) {
+ rcu_read_unlock();
dev_err(dev, "Invalid initial frequency %lu kHz.\n",
exynos4_devfreq_profile.initial_freq);
return PTR_ERR(opp);
}
- data->curr_opp = opp;
+ data->curr_oppinfo.rate = opp_get_freq(opp);
+ data->curr_oppinfo.volt = opp_get_voltage(opp);
+ rcu_read_unlock();
platform_set_drvdata(pdev, data);
--
1.7.9.5
--
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