Re: [PATCH v6 10/11] cpuidle/powernv: Add support for POWER ISA v3 idle states

Shreyas B Prabhu
2016-06-14T10:47:30Z

On 06/13/2016 09:04 PM, Daniel Lezcano wrote:
> On Wed, Jun 08, 2016 at 11:54:30AM -0500, Shreyas B. Prabhu wrote:
>> POWER ISA v3 defines a new idle processor core mechanism. In summary,
>> a) new instruction named stop is added.
>> b) new per thread SPR named PSSCR is added which controls the behavior
>> of stop instruction.
>>
>> Supported idle states and value to be written to PSSCR register to enter
>> any idle state is exposed via ibm,cpu-idle-state-names and
>> ibm,cpu-idle-state-psscr respectively. To enter an idle state,
>> platform provided power_stop() needs to be invoked with the appropriate
>> PSSCR value.
>>
>> This patch adds support for this new mechanism in cpuidle powernv driver.
>>
>> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
>> Cc: Rob Herring <robh+dt@kernel.org>
>> Cc: Lorenzo Pieralisi <Lorenzo.Pieralisi@arm.com>
>> Cc: linux-pm@vger.kernel.org
>> Cc: Michael Ellerman <mpe@ellerman.id.au>
>> Cc: Paul Mackerras <paulus@ozlabs.org>
>> Cc: linuxppc-dev@lists.ozlabs.org
>> Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
>> Signed-off-by: Shreyas B. Prabhu <shreyas@linux.vnet.ibm.com>
>> ---
>
> [ ... ]
>
>> + rc = of_property_read_string_array(power_mgt,
>> + "ibm,cpu-idle-state-names", names,
>> + dt_idle_states);
>> + if (rc < 0) {
>> + pr_warn("cpuidle-powernv: missing ibm,cpu-idle-state-names in DT\n");
>> + goto out_free_latency;
>> + }
>> +
>> + /*
>> + * If the idle states use stop instruction, probe for psscr values
>> + * which are necessary to specify required stop level.
>> + */
>> + if (flags[0] & (OPAL_PM_STOP_INST_FAST | OPAL_PM_STOP_INST_DEEP)) {
>> + psscr_val = kcalloc(dt_idle_states, sizeof(*psscr_val),
>> + GFP_KERNEL);
>
> if (!psscr_val) check missing.

I ignored adding this check because this is part of initcall and we are
unlikely to run out of memory at this state. But I'll add the check in
next version.
>
>> + rc = of_property_read_u64_array(power_mgt,
>> + "ibm,cpu-idle-state-psscr",
>> + psscr_val, dt_idle_states);
>> + if (rc) {
>> + pr_warn("cpuidle-powernv: missing ibm,cpu-idle-states-psscr in DT\n");
>> + goto out_free_psscr;
>> + }
>> + }
>> residency_ns = kzalloc(sizeof(*residency_ns) * dt_idle_states, GFP_KERNEL);
>
> if (!residency_ns) check missing.
>
> I suppose the code is relying on 'of_property_read_u32_array' to check it,
> right ?

I'll add the NULL check for existing kzalloc's in the file as well in
the next version.

Thanks,
Shreyas