linux-kernel - Re: [RFC-V3 1/2] mailbox: pcc: Add processing platform notification for slave subspaces

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Message-ID: <e96474e8-6427-9a80-0e97-de97684b8e40@xsightlabs.com>
Date:   Mon, 13 Feb 2023 16:18:51 -0500
From:   Robbie King <robbiek@...ghtlabs.com>
To:     "lihuisong (C)" <lihuisong@...wei.com>,
        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, zhangzekun11@...wei.com,
        wangxiongfeng2@...wei.com, tanxiaofei@...wei.com,
        guohanjun@...wei.com, xiexiuqi@...wei.com,
        wangkefeng.wang@...wei.com, huangdaode@...wei.com
Subject: Re: [RFC-V3 1/2] mailbox: pcc: Add processing platform notification
 for slave subspaces

On 2/6/2023 9:27 PM, lihuisong (C) wrote:
> 
> 在 2023/2/6 23:39, Sudeep Holla 写道:
>> Hi Huisong,
>>
>> Apologies for such a long delay.
>>
>> Also I would like to hear from Robbie King who I know is playing around
>> with this these days 😄. At minimum if this logic works for him as well.
> 
> @Robbie King,
> Do you use this patchset to test your requirements?
> Any other problems? Can you tell us your result?
> 

Sorry for the delay.  I have verified the two patches continue to pass the
limited stress testing I have done with earlier change sets.

>>
>> On Sat, Dec 03, 2022 at 05:51:49PM +0800, Huisong Li wrote:
>>> Currently, PCC driver doesn't support the processing of platform
>>> notification for slave PCC subspaces because of the incomplete
>>> communication flow.
>>>
>>> According to ACPI specification, if platform sends a notification
>>> to OSPM, it must clear the command complete bit and trigger platform
>>> interrupt. OSPM needs to check whether the command complete bit is
>>> cleared, clear platform interrupt, process command, and then set the
>>> command complete and ring doorbell to Platform. But the current judgment
>>> on the command complete is not applicable to type4 in pcc_mbox_irq().
>>>
>>> This patch introduces a communication flow direction field to detect
>>> whether the interrupt belongs to the master or slave subspace channel.
>>> And PCC driver needs to add the phase of setting the command complete
>>> and ring doorbell in pcc_mbox_irq() to complete type4 communication
>>> flow after processing command from Platform.
>>>
>>> Signed-off-by: Huisong Li <lihuisong@...wei.com>
>>> ---
>>>   drivers/mailbox/pcc.c | 77 +++++++++++++++++++++++++++++++++++++++----
>>>   1 file changed, 71 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
>>> index 105d46c9801b..ad6d0b7d50fc 100644
>>> --- a/drivers/mailbox/pcc.c
>>> +++ b/drivers/mailbox/pcc.c
>>> @@ -80,6 +80,13 @@ struct pcc_chan_reg {
>>>       u64 status_mask;
>>>   };
>>>   +enum pcc_chan_comm_flow_dir_type {
>>> +    PCC_ONLY_OSPM_TO_PLATFORM,
>>> +    PCC_ONLY_PLATFORM_TO_OSPM,
>>> +    PCC_BIDIRECTIONAL,
>>> +    PCC_DIR_UNKNOWN,
>>> +};
>>> +
>>>   /**
>>>    * struct pcc_chan_info - PCC channel specific information
>>>    *
>>> @@ -91,6 +98,7 @@ struct pcc_chan_reg {
>>>    * @cmd_update: PCC register bundle for the command complete update register
>>>    * @error: PCC register bundle for the error status register
>>>    * @plat_irq: platform interrupt
>>> + * @comm_flow_dir: direction of communication flow supported by the channel
>>>    */
>>>   struct pcc_chan_info {
>>>       struct pcc_mbox_chan chan;
>>> @@ -100,12 +108,15 @@ struct pcc_chan_info {
>>>       struct pcc_chan_reg cmd_update;
>>>       struct pcc_chan_reg error;
>>>       int plat_irq;
>>> +    u8 comm_flow_dir;
>> I would rather just save the 'type' as read from the PCCT. We don't know
>> what future types might be and just identifying them by the direction of
>> flow of the data, it restricts the usage of this.
> Ack.
>>
>>>   };
>>>     #define to_pcc_chan_info(c) container_of(c, struct pcc_chan_info, chan)
>>>   static struct pcc_chan_info *chan_info;
>>>   static int pcc_chan_count;
>>>   +static int pcc_send_data(struct mbox_chan *chan, void *data);
>>> +
>>>   /*
>>>    * PCC can be used with perf critical drivers such as CPPC
>>>    * So it makes sense to locally cache the virtual address and
>>> @@ -221,6 +232,43 @@ static int pcc_map_interrupt(u32 interrupt, u32 flags)
>>>       return acpi_register_gsi(NULL, interrupt, trigger, polarity);
>>>   }
>>>   +static bool pcc_chan_need_rsp_irq(struct pcc_chan_info *pchan,
>>> +                  u64 cmd_complete_reg_val)
>> Probably rename this as pcc_chan_command_complete or something similar.
> Ack
>>
>>> +{
>>> +    bool need_rsp;
>>> +
>>> +    if (!pchan->cmd_complete.gas)
>>> +        return true;
>>> +
>>> +    cmd_complete_reg_val &= pchan->cmd_complete.status_mask;
>>> +
>>> +    switch (pchan->comm_flow_dir) {
>> Use the channel type instead here.
> Ack