[PATCH] arm64: skip register_cpufreq_notifier on ACPI-based systems

[Christopher Covington]

On 01/25/2017 07:03 AM, Juri Lelli wrote:
> Hi,
> 
> On 24/01/17 17:43, Prashanth Prakash wrote:
>> On ACPI based systems where the topology is setup using the API
>> store_cpu_topology, at the moment we do not have necessary code
>> to handle a cpufreq notifier, thus resulting in a crash.
>>
>> Skip register_cpufreq_notifier if raw_capacity is not allocated
>> as part of topology initialization.
>>
>> Stack:
>>         init_cpu_capacity_callback+0xb4/0x1c8
>>         notifier_call_chain+0x5c/0xa0
>>         __blocking_notifier_call_chain+0x58/0xa0
>>         blocking_notifier_call_chain+0x3c/0x50
>>         cpufreq_set_policy+0xe4/0x328
>>         cpufreq_init_policy+0x80/0x100
>>         cpufreq_online+0x418/0x710
>>         cpufreq_add_dev+0x118/0x180
>>         subsys_interface_register+0xa4/0xf8
>>         cpufreq_register_driver+0x1c0/0x298
>>         cppc_cpufreq_init+0xdc/0x1000 [cppc_cpufreq]
>>         do_one_initcall+0x5c/0x168
>>         do_init_module+0x64/0x1e4
>>         load_module+0x130c/0x14d0
>>         SyS_finit_module+0x108/0x120
>>         el0_svc_naked+0x24/0x28
>>
>> Patch that added support for popultaing cpu capacity for DT:
>> https://patchwork.codeaurora.org/patch/98353/

In other words,

Fixes: 7202bde8b7ae ("arm64: parse cpu capacity-dmips-mhz from DT")

>> Signed-off-by: Prashanth Prakash <pprakash at codeaurora.org>
>> ---
>>  arch/arm64/kernel/topology.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
>> index 23e9e13..3f175ce 100644
>> --- a/arch/arm64/kernel/topology.c
>> +++ b/arch/arm64/kernel/topology.c
>> @@ -209,7 +209,7 @@ static void normalize_cpu_capacity(void)
>>  
>>  static int __init register_cpufreq_notifier(void)
>>  {
>> -	if (cap_parsing_failed)
>> +	if (cap_parsing_failed || !raw_capacity)
> 
> Looks good. I couldn't really test it to check if it fixes your problem
> (I assume it does), but it doesn't seem to introduce regressions on my
> boxes.

Are you testing on QEMU or Fast Models? I was under the impression that the
former had ACPI support. For the latter, wouldn't it be nice to have ACPI
support in the bootwrapper. Out of curiosity, is Mark's bootwrapper
repository on kernel.org the best one to use these days?

http://git.kernel.org/cgit/linux/kernel/git/mark/boot-wrapper-aarch64.git/

Thanks,
Cov

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