linux-kernel - Re: [PATCH 2/2] mailbox: pcc: Support shared interrupt for multiple subspaces

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Date:   Fri, 3 Mar 2023 11:14:07 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     "lihuisong (C)" <lihuisong@...wei.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
Subject: Re: [PATCH 2/2] mailbox: pcc: Support shared interrupt for multiple
 subspaces

On Fri, Mar 03, 2023 at 02:33:49PM +0800, lihuisong (C) wrote:
> Sorry for my resend. Because I found that my last reply email is not in the
> thread of this patch. I guess it may be send failed.
> 
> 在 2023/3/2 22:02, Sudeep Holla 写道:
> > No. I meant a comment saying it is not need since only one transfer can occur
> > at a time and mailbox takes care of locking. So chan_in_use can be accessed
> > without a lock.
> Got it. Agreed.

Thanks

> > > For types no need this flag, it is always hard to understand and redundant
> > > design.
> > But does it matter ? You can even support shared interrupt for type 1&2.
> BTW, type 1 subspaces do not support a level triggered platform interrupt as
> no method is provided to clear the interrupt.

Agreed but there is no harm using the flag, you can add a comment that it is
useful only if shared interrupts are supported. That will imply it is dummy
for type 1. I am avoiding too many type unnecessary checks especially in IRQ
handler.

> > They support level interrupt, so we can add them too. I understand you can
> > test only type 3, but this driver caters for all and the code must be generic
> > as much as possible. I don't see any point in check for type 3 only. Only
> I understand what you do.
> But type 2 also supports the communication flow from OSPM to Platfrom.
> In this case, this flag will get in the way of type 2.
>

How ?

> Whether the interrupt belongs to a type2 channel is only determined by
> the status field in Generic Communications Channel Shared Memory Region,
> which is done in rx_callback of PCC client.

Agreed, but do you see any issue using the flag even if it acts as dummy ?

--
Regards,
Sudeep