From: "liwei (JK)" <liwei728@huawei.com>
To: Pierre Gondois <pierre.gondois@arm.com>
Cc: <linux-acpi@vger.kernel.org>, <rafael@kernel.org>,
<linux-kernel@vger.kernel.org>, <lenb@kernel.org>,
<liwei391@huawei.com>, <viresh.kumar@linaro.org>
Subject: Re: [PATCH] cpufreq/cppc: fix perf_to_khz conversion exception
Date: Mon, 6 May 2024 10:55:09 +0800 [thread overview]
Message-ID: <df3d5556-30b1-42d9-aecc-1ad155f024bc@huawei.com> (raw)
In-Reply-To: <0f8ccc3d-46ca-4632-9ecf-5da596ad5a1a@arm.com>
Hello Pierre,
Thanks for your reminder.
在 2024/5/3 15:42, Pierre Gondois 写道:
> Hello Liwei,
>
> Thanks for the fix. I think there might be a similar issue
> in cppc_khz_to_perf(),
>
> Regards,
> Pierre
>
cppc_khz_to_perf() also has similar issue, I will modify the patch again.
Liwei
> On 4/30/24 12:12, liwei wrote:
>> When the nominal_freq recorded by the kernel is equal to lowest_freq and
>> the frequency reduction operation is triggered externally, there is a
>> conversion logic error in cppc_perf_to_khz(), causing the kernel to be
>> unable to feedback the true frequency.
>>
>> Fix this by adding the branch processing logic when nominal_freq is equal
>> to lowest_freq.
>>
>> Fixes: ec1c7ad47664 ("cpufreq: CPPC: Fix performance/frequency
>> conversion")
>> Signed-off-by: liwei <liwei728@huawei.com>
>> ---
>> drivers/acpi/cppc_acpi.c | 10 ++++++++--
>> 1 file changed, 8 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
>> index a40b6f3946ef..92aac6974e0e 100644
>> --- a/drivers/acpi/cppc_acpi.c
>> +++ b/drivers/acpi/cppc_acpi.c
>> @@ -1869,9 +1869,15 @@ unsigned int cppc_perf_to_khz(struct
>> cppc_perf_caps *caps, unsigned int perf)
>> u64 mul, div;
>> if (caps->lowest_freq && caps->nominal_freq) {
>> - mul = caps->nominal_freq - caps->lowest_freq;
>> + /* Avoid the special case when nominal_freq is equal to
>> lowest_freq */
>> + if (caps->lowest_freq == caps->nominal_freq) {
>> + mul = caps->nominal_freq;
>> + div = caps->nominal_perf;
>> + } else {
>> + mul = caps->nominal_freq - caps->lowest_freq;
>> + div = caps->nominal_perf - caps->lowest_perf;
>> + }
>> mul *= KHZ_PER_MHZ;
>> - div = caps->nominal_perf - caps->lowest_perf;
>> offset = caps->nominal_freq * KHZ_PER_MHZ -
>> div64_u64(caps->nominal_perf * mul, div);
>> } else {
prev parent reply other threads:[~2024-05-06 2:55 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-30 10:12 [PATCH] cpufreq/cppc: fix perf_to_khz conversion exception liwei
2024-05-03 7:42 ` Pierre Gondois
2024-05-06 2:55 ` liwei (JK) [this message]
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