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SubjectRe: [PATCH] firmware: arm_scmi: fix divide by zero when sustained_perf_level is zero
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On 06/09/18 14:17, Quentin Perret wrote:
> Hi Sudeep,
>
> On Wednesday 05 Sep 2018 at 17:38:11 (+0100), Sudeep Holla wrote:
>> @@ -166,7 +166,12 @@ scmi_perf_domain_attributes_get(const struct scmi_handle *handle, u32 domain,
>> le32_to_cpu(attr->sustained_freq_khz);
>> dom_info->sustained_perf_level =
>> le32_to_cpu(attr->sustained_perf_level);
>> - dom_info->mult_factor = (dom_info->sustained_freq_khz * 1000) /
>> + if (!dom_info->sustained_freq_khz ||
>> + !dom_info->sustained_perf_level)
>> + dom_info->mult_factor = 1;
>
> I'm sorry I missed that the first time I reviewed this patch, but after
> discussing with Ionela, we found out that there is actually a case where
> this could be a problem. If you have perf levels that are 1,2,3,4 (for
> example), then with mult_factor=1 you'll register OPPs at 1Hz, 2Hz, 3Hz,
> 4Hz into PM_OPP. And that will be turned into 0 KHz for all of them at
> the CPUFreq level when divided by 1000 in dev_pm_opp_init_cpufreq_table().
>

Good find.

> I guess a quick fix would be to have a default mult_factor of 1000 ...
>

I agree.

> What do you think ?

I will respin and send.

--
Regards,
Sudeep

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