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[PATCH -next] PM / OPP: Fix crash seen if CPU clock has no voltage regulator

Started byGuenter Roeck <linux@roeck-us.net>
First post2016-02-15 20:40 +0100
Last post2016-02-16 01:50 +0100
Articles 3 — 3 participants

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  [PATCH -next] PM / OPP: Fix crash seen if CPU clock has no voltage regulator Guenter Roeck <linux@roeck-us.net> - 2016-02-15 20:40 +0100
    Re: [PATCH -next] PM / OPP: Fix crash seen if CPU clock has no  voltage regulator kbuild test robot <lkp@intel.com> - 2016-02-16 01:20 +0100
    Re: [PATCH -next] PM / OPP: Fix crash seen if CPU clock has no  voltage regulator Viresh Kumar <viresh.kumar@linaro.org> - 2016-02-16 01:50 +0100

#1334762 — [PATCH -next] PM / OPP: Fix crash seen if CPU clock has no voltage regulator

FromGuenter Roeck <linux@roeck-us.net>
Date2016-02-15 20:40 +0100
Subject[PATCH -next] PM / OPP: Fix crash seen if CPU clock has no voltage regulator
Message-ID<r2xa3-5vB-49@gated-at.bofh.it>
omap3 overo boots crash with

Unable to handle kernel NULL pointer dereference at virtual address 00000030
pgd = c0204000
[00000030] *pgd=00000000
Internal error: Oops: 17 [#1] SMP ARM
...
[] (regulator_set_voltage) from [] (_set_opp_voltage+0x34/0x90)
[] (_set_opp_voltage) from [] (dev_pm_opp_set_rate+0x19c/0x288)
[] (dev_pm_opp_set_rate) from [] (__cpufreq_driver_target+0x17c/0x29c)
[] (__cpufreq_driver_target) from [] (dbs_check_cpu+0x19c/0x1e4)
[] (dbs_check_cpu) from [] (cpufreq_governor_dbs+0x308/0x5c4)
[] (cpufreq_governor_dbs) from [] (__cpufreq_governor+0x20c/0x24c)
[] (__cpufreq_governor) from [] (cpufreq_init_policy+0x60/0x8c)
[] (cpufreq_init_policy) from [] (cpufreq_online+0x2cc/0x6d8)
[] (cpufreq_online) from [] (subsys_interface_register+0x80/0xc4)
[] (subsys_interface_register) from [] (cpufreq_register_driver+0x144/0x1a0)
[] (cpufreq_register_driver) from [] (dt_cpufreq_probe+0x64/0xe8)
[] (dt_cpufreq_probe) from [] (platform_drv_probe+0x50/0xb0)
[] (platform_drv_probe) from [] (driver_probe_device+0x1f4/0x2b0)
...

Analysis shows that regulator==NULL in regulator_set_voltage().
Code around _set_opp_voltage() suggests that having no voltage regulator
attached to a CPU clock is valid, so do not attempt to set a voltage
in that case.

Fixes: 6a0712f6f199e ("PM / OPP: Add dev_pm_opp_set_rate()"
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 drivers/base/power/opp/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/power/opp/core.c b/drivers/base/power/opp/core.c
index d7cd4e265766..82ad5ae72427 100644
--- a/drivers/base/power/opp/core.c
+++ b/drivers/base/power/opp/core.c
@@ -564,7 +564,7 @@ static int _set_opp_voltage(struct device *dev, struct regulator *reg,
 	int ret;
 
 	/* Regulator not available for device */
-	if (IS_ERR(reg)) {
+	if (IS_ERR_OR_NULL(reg)) {
 		dev_dbg(dev, "%s: regulator not available: %ld\n", __func__,
 			PTR_ERR(reg));
 		return 0;
-- 
2.5.0

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#1334884 — Re: [PATCH -next] PM / OPP: Fix crash seen if CPU clock has no voltage regulator

Fromkbuild test robot <lkp@intel.com>
Date2016-02-16 01:20 +0100
SubjectRe: [PATCH -next] PM / OPP: Fix crash seen if CPU clock has no voltage regulator
Message-ID<r2Bx0-8q7-5@gated-at.bofh.it>
In reply to#1334762

[Multipart message — attachments visible in raw view] — view raw

Hi Jon,

[auto build test WARNING on next-20160215]

url:    https://github.com/0day-ci/linux/commits/Jon-Hunter/PM-OPP-Fix-NULL-pointer-dereference-crash-when-setting-the-OPP/20160215-220238
config: x86_64-randconfig-s0-02160737 (attached as .config)
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings

All warnings (new ones prefixed by >>):

   drivers/base/power/opp/core.c: In function 'dev_pm_opp_set_rate':
>> drivers/base/power/opp/core.c:603:38: warning: 'ou_volt_max' may be used uninitialized in this function [-Wmaybe-uninitialized]
     unsigned long ou_volt, ou_volt_min, ou_volt_max;
                                         ^
>> drivers/base/power/opp/core.c:603:25: warning: 'ou_volt_min' may be used uninitialized in this function [-Wmaybe-uninitialized]
     unsigned long ou_volt, ou_volt_min, ou_volt_max;
                            ^
>> drivers/base/power/opp/core.c:603:16: warning: 'ou_volt' may be used uninitialized in this function [-Wmaybe-uninitialized]
     unsigned long ou_volt, ou_volt_min, ou_volt_max;
                   ^

vim +/ou_volt_max +603 drivers/base/power/opp/core.c

6a0712f6 Viresh Kumar 2016-02-09  587   * @dev:	 device for which we do this operation
6a0712f6 Viresh Kumar 2016-02-09  588   * @target_freq: frequency to achieve
6a0712f6 Viresh Kumar 2016-02-09  589   *
6a0712f6 Viresh Kumar 2016-02-09  590   * This configures the power-supplies and clock source to the levels specified
6a0712f6 Viresh Kumar 2016-02-09  591   * by the OPP corresponding to the target_freq.
6a0712f6 Viresh Kumar 2016-02-09  592   *
6a0712f6 Viresh Kumar 2016-02-09  593   * Locking: This function takes rcu_read_lock().
6a0712f6 Viresh Kumar 2016-02-09  594   */
6a0712f6 Viresh Kumar 2016-02-09  595  int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
6a0712f6 Viresh Kumar 2016-02-09  596  {
6a0712f6 Viresh Kumar 2016-02-09  597  	struct device_opp *dev_opp;
6a0712f6 Viresh Kumar 2016-02-09  598  	struct dev_pm_opp *old_opp, *opp;
6a0712f6 Viresh Kumar 2016-02-09  599  	struct regulator *reg;
6a0712f6 Viresh Kumar 2016-02-09  600  	struct clk *clk;
6a0712f6 Viresh Kumar 2016-02-09  601  	unsigned long freq, old_freq;
6a0712f6 Viresh Kumar 2016-02-09  602  	unsigned long u_volt, u_volt_min, u_volt_max;
6a0712f6 Viresh Kumar 2016-02-09 @603  	unsigned long ou_volt, ou_volt_min, ou_volt_max;
6a0712f6 Viresh Kumar 2016-02-09  604  	int ret;
6a0712f6 Viresh Kumar 2016-02-09  605  
6a0712f6 Viresh Kumar 2016-02-09  606  	if (unlikely(!target_freq)) {
6a0712f6 Viresh Kumar 2016-02-09  607  		dev_err(dev, "%s: Invalid target frequency %lu\n", __func__,
6a0712f6 Viresh Kumar 2016-02-09  608  			target_freq);
6a0712f6 Viresh Kumar 2016-02-09  609  		return -EINVAL;
6a0712f6 Viresh Kumar 2016-02-09  610  	}
6a0712f6 Viresh Kumar 2016-02-09  611  

:::::: The code at line 603 was first introduced by commit
:::::: 6a0712f6f199e737aa5913d28ec4bd3a25de9660 PM / OPP: Add dev_pm_opp_set_rate()

:::::: TO: Viresh Kumar <viresh.kumar@linaro.org>
:::::: CC: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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#1334888 — Re: [PATCH -next] PM / OPP: Fix crash seen if CPU clock has no voltage regulator

FromViresh Kumar <viresh.kumar@linaro.org>
Date2016-02-16 01:50 +0100
SubjectRe: [PATCH -next] PM / OPP: Fix crash seen if CPU clock has no voltage regulator
Message-ID<r2C01-aC-1@gated-at.bofh.it>
In reply to#1334762
On 15-02-16, 11:34, Guenter Roeck wrote:
> omap3 overo boots crash with
> 
> Unable to handle kernel NULL pointer dereference at virtual address 00000030
> pgd = c0204000
> [00000030] *pgd=00000000
> Internal error: Oops: 17 [#1] SMP ARM
> ...
> [] (regulator_set_voltage) from [] (_set_opp_voltage+0x34/0x90)
> [] (_set_opp_voltage) from [] (dev_pm_opp_set_rate+0x19c/0x288)
> [] (dev_pm_opp_set_rate) from [] (__cpufreq_driver_target+0x17c/0x29c)
> [] (__cpufreq_driver_target) from [] (dbs_check_cpu+0x19c/0x1e4)
> [] (dbs_check_cpu) from [] (cpufreq_governor_dbs+0x308/0x5c4)
> [] (cpufreq_governor_dbs) from [] (__cpufreq_governor+0x20c/0x24c)
> [] (__cpufreq_governor) from [] (cpufreq_init_policy+0x60/0x8c)
> [] (cpufreq_init_policy) from [] (cpufreq_online+0x2cc/0x6d8)
> [] (cpufreq_online) from [] (subsys_interface_register+0x80/0xc4)
> [] (subsys_interface_register) from [] (cpufreq_register_driver+0x144/0x1a0)
> [] (cpufreq_register_driver) from [] (dt_cpufreq_probe+0x64/0xe8)
> [] (dt_cpufreq_probe) from [] (platform_drv_probe+0x50/0xb0)
> [] (platform_drv_probe) from [] (driver_probe_device+0x1f4/0x2b0)
> ...
> 
> Analysis shows that regulator==NULL in regulator_set_voltage().
> Code around _set_opp_voltage() suggests that having no voltage regulator
> attached to a CPU clock is valid, so do not attempt to set a voltage
> in that case.
> 
> Fixes: 6a0712f6f199e ("PM / OPP: Add dev_pm_opp_set_rate()"
> Cc: Viresh Kumar <viresh.kumar@linaro.org>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
>  drivers/base/power/opp/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Sorry about that, a separate fix for the same is pushed by Rafael in
pm/linux-next now.

-- 
viresh

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