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PM / devfreq: exynos4_bus: honor RCU lock usage
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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@ti.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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Nishanth Menon authored and Rafael J. Wysocki committed Jan 22, 2013
1 parent bcb2754 commit 8fa938a
Showing 1 changed file with 67 additions and 27 deletions.
94 changes: 67 additions & 27 deletions drivers/devfreq/exynos4_bus.c
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Original file line number Diff line number Diff line change
Expand Up @@ -73,14 +73,24 @@ 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;
struct devfreq *devfreq;
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;
Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -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:
Expand All @@ -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;
}
Expand All @@ -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:
Expand All @@ -626,35 +639,45 @@ 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);

if (data->disabled)
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;
Expand All @@ -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;
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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;

Expand All @@ -943,26 +968,37 @@ 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;
}
if (err)
goto unlock;

data->curr_opp = opp;
data->curr_oppinfo = new_oppinfo;
unlock:
mutex_unlock(&data->lock);
if (err)
Expand Down Expand Up @@ -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);

Expand Down

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