linux-kernel - Re: [PATCH 1/2] ACPI: PCC: replace wait_for

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Message-ID: <cb2f3c9c-ab45-357d-8a56-1c64b535633c@huawei.com>
Date:   Thu, 22 Sep 2022 10:29:06 +0800
From:   "lihuisong (C)" <lihuisong@...wei.com>
To:     Sudeep Holla <sudeep.holla@....com>
CC:     <linux-acpi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <rafael@...nel.org>, <rafael.j.wysocki@...el.com>,
        <wanghuiqiang@...wei.com>, <huangdaode@...wei.com>
Subject: Re: [PATCH 1/2] ACPI: PCC: replace wait_for_completion()


在 2022/9/21 23:47, Sudeep Holla 写道:
> On Tue, Sep 20, 2022 at 05:44:59PM +0800, Huisong Li wrote:
>> Currently, the function waiting for completion of mailbox operation is
>> 'wait_for_completion()'.  The PCC method will be permanently blocked if
>> this mailbox message fails to execute. So this patch replaces it with
>> 'wait_for_completion_timeout()'. And set the timeout interval to an
>> arbitrary retries on top of nominal to prevent the remote processor is
>> slow to respond to PCC commands.
>>
> Sounds good to me. The only concern(may be not serious) is what happens
> if we receive response from the platform after the timeout. I have tested
If OS still cann't receive response in noramal latency(must be filled 
accurately
as protocol said) + retries, there is a high probability that an 
exception occurs.
Even if we receive response after the timeout, I think there may be no 
impact,
but the response data in PCC share memory is ignored.
> for that in non ACPI non PCC context. I don't have a setup to trigger that
> with ACPI PCC + this patch to test. Other than that, I am fine with this:
>
> Reviewed-by: Sudeep Holla <sudeep.holla@....com>
>