cpufreq: powernv: fix stack bloat and hard limit on number of CPUs

commit db0d32d84031188443e25edbd50a71a6e7ac5d1d upstream.

The following build warning occurred on powerpc 64-bit builds:

drivers/cpufreq/powernv-cpufreq.c: In function 'init_chip_info':
drivers/cpufreq/powernv-cpufreq.c:1070:1: warning: the frame size of
1040 bytes is larger than 1024 bytes [-Wframe-larger-than=]

This is with a cross-compiler based on gcc 8.1.0, which I got from:
  https://mirrors.edge.kernel.org/pub/tools/crosstool/files/bin/x86_64/8.1.0/

The warning is due to putting 1024 bytes on the stack:

    unsigned int chip[256];

...and it's also undesirable to have a hard limit on the number of
CPUs here.

Fix both problems by dynamically allocating based on num_possible_cpus,
as recommended by Michael Ellerman.

Fixes: 053819e0bf840 ("cpufreq: powernv: Handle throttling due to Pmax capping at chip level")
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: 4.10+ <stable@vger.kernel.org> # 4.10+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
index bf6519c..5fff39d 100644 (file)
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c
@@ -1042,9 +1042,14 @@ static struct cpufreq_driver powernv_cpufreq_driver = {
 
 static int init_chip_info(void)
 {
-       unsigned int chip[256];
+       unsigned int *chip;
        unsigned int cpu, i;
        unsigned int prev_chip_id = UINT_MAX;
+       int ret = 0;
+
+       chip = kcalloc(num_possible_cpus(), sizeof(*chip), GFP_KERNEL);
+       if (!chip)
+               return -ENOMEM;
 
        for_each_possible_cpu(cpu) {
                unsigned int id = cpu_to_chip_id(cpu);
@@ -1056,8 +1061,10 @@ static int init_chip_info(void)
        }
 
        chips = kcalloc(nr_chips, sizeof(struct chip), GFP_KERNEL);
-       if (!chips)
-               return -ENOMEM;
+       if (!chips) {
+               ret = -ENOMEM;
+               goto free_and_return;
+       }
 
        for (i = 0; i < nr_chips; i++) {
                chips[i].id = chip[i];
@@ -1067,7 +1074,9 @@ static int init_chip_info(void)
                        per_cpu(chip_info, cpu) =  &chips[i];
        }
 
-       return 0;
+free_and_return:
+       kfree(chip);
+       return ret;
 }
 
 static inline void clean_chip_info(void)