linux-kernel - Re: [PATCH 1/2] mailbox: pcc: Add processing platform notification for slave subspaces

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Date:   Sat, 4 Mar 2023 17:49:44 +0800
From:   "lihuisong (C)" <lihuisong@...wei.com>
To:     Sudeep Holla <sudeep.holla@....com>
CC:     <robbiek@...ghtlabs.com>, <linux-acpi@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <rafael@...nel.org>,
        <rafael.j.wysocki@...el.com>, <wanghuiqiang@...wei.com>,
        <zhangzekun11@...wei.com>, <wangxiongfeng2@...wei.com>,
        <tanxiaofei@...wei.com>, <guohanjun@...wei.com>,
        <xiexiuqi@...wei.com>, <wangkefeng.wang@...wei.com>,
        <huangdaode@...wei.com>, <lihuisong@...wei.com>
Subject: Re: [PATCH 1/2] mailbox: pcc: Add processing platform notification
 for slave subspaces


在 2023/3/3 19:07, Sudeep Holla 写道:
> On Fri, Mar 03, 2023 at 09:50:00AM +0800, lihuisong (C) wrote:
>> 在 2023/3/2 21:52, Sudeep Holla 写道:
>>> On Thu, Mar 02, 2023 at 09:57:35AM +0800, lihuisong (C) wrote:
>>>> 在 2023/3/1 21:24, Sudeep Holla 写道:
>>> [...]
>>>
>>>>> +static bool pcc_mbox_cmd_complete_check(struct pcc_chan_info *pchan)
>>>>> +{
>>>>> +       u64 val;
>>>>> +       int ret;
>>>>> +
>>>>> +       ret = pcc_chan_reg_read(&pchan->cmd_complete, &val);
>>>>> +       if (ret)
>>>>> +               return false;
>>>>> +
>>>> we indeed already check if cmd_complete register is exist.
>>>> IMO, it can simply the code logic and reduce the risk of problems if we
>>>> return true here for the type without this register.
>>>> what do you think?
>>>>
>>> IIUC, your concern is about returning true for type 4 when the register
>>> doesn't exist, right ?
>> Return true in advance for the type without the cmd_complete register.
>> If support the register, we judge if the channel should respond the
>> interrupt based on the value of cmd_complete, like bellow.
> Right, sorry for missing that.
>
>> -->8
>> +static bool pcc_mbox_cmd_complete_check(struct pcc_chan_info *pchan)
>> +{
>> +       u64 val;
>> +       int ret;
>> +
>> +       ret = pcc_chan_reg_read(&pchan->cmd_complete, &val);
>> +       if (ret)
>> +               return false;
>> +
>> +        if (!pchan->cmd_complete.gas)
>> +                return true;
>> +
> Yes we need the above check.
>
>> +       /*
>> +         * Judge if the channel respond the interrupt based on the value of
>> +         * command complete.
>> +         */
>> +       val &= pchan->cmd_complete.status_mask;
>> +       /*
>> +        * If this is PCC slave subspace channel, then the command complete
>> +        * bit 0 indicates that Platform is sending a notification and OSPM
>> +        * needs to respond this interrupt to process this command.
>> +        */
>> +       if (pchan->type == ACPI_PCCT_TYPE_EXT_PCC_SLAVE_SUBSPACE)
>> +               return !val;
>> +       else
>> +               return !!val;
>> +}
>>> I am saying it won't happen as we bail out if there is no GAS register
>>> from pcc_chan_reg_init(). Or am I missing something here ?
>> Yes, what you say is also ok. Just wondering if it is better to simply the
>> logic.
> Understood now.
>
>>>>> +       val &= pchan->cmd_complete.status_mask;
>>>>> +
>>>>> +       /*
>>>>> +        * If this is PCC slave subspace channel, then the command complete
>>>>> +        * bit 0 indicates that Platform is sending a notification and OSPM
>>>>> +        * needs to respond this interrupt to process this command.
>>>>> +        */
>>>>> +       if (pchan->type == ACPI_PCCT_TYPE_EXT_PCC_SLAVE_SUBSPACE)
>>>>> +               return !val;
>>>>> +       else
>>>>> +               return !!val;
>>>> This else branch is not applicable to type 3. type 3 will cannot respond
>>>> interrupt.
>>> Sorry I don't understand what you mean by that.
>> Sorry for my mistake.
>> I meant that the type2 channel always return false in this function and
>> never respond the interrupt if no check for the GAS register.
>> Because the 'val' for the type without the register is zero.
> Agreed as mentioned above, we need to bail out with true return if no GAS is
> found.
>
Ok, I will fix it as mentioned above.
>
> .