linux-kernel - Re: [PATCH v2 1/2] mailbox: add async request mechanism to empower controllers w/ hw queues

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Message-ID: <CABb+yY0_NSLAs-mP=vHeNsfKRcS2hcFWmWfcvsr=nFcXQOi5uA@mail.gmail.com>
Date: Thu, 17 Oct 2024 23:17:50 -0500
From: Jassi Brar <jassisinghbrar@...il.com>
To: Tudor Ambarus <tudor.ambarus@...aro.org>
Cc: krzk@...nel.org, alim.akhtar@...sung.com, mst@...hat.com, 
	javierm@...hat.com, tzimmermann@...e.de, bartosz.golaszewski@...aro.org, 
	luzmaximilian@...il.com, sudeep.holla@....com, conor.dooley@...rochip.com, 
	bjorn@...osinc.com, ulf.hansson@...aro.org, linux-samsung-soc@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	marcan@...can.st, neal@...pa.dev, alyssa@...enzweig.io, broonie@...nel.org, 
	andre.draszik@...aro.org, willmcvicker@...gle.com, peter.griffin@...aro.org, 
	kernel-team@...roid.com, vincent.guittot@...aro.org, 
	daniel.lezcano@...aro.org
Subject: Re: [PATCH v2 1/2] mailbox: add async request mechanism to empower
 controllers w/ hw queues

On Thu, Oct 17, 2024 at 11:36 AM Tudor Ambarus <tudor.ambarus@...aro.org> wrote:
>
> Current form of the mailbox framework doesn't allow controllers to benefit
> of their hardware queue capabilities as the framework handles a single
> active request at a time.
>
> The active request is considered completed when TX completes. But it seems
> that TX is not in direct relation with RX,
>
Correct, and it is not meant to be.
You are assuming there is always an RX in response to a TX, which is
not the case. Many platforms just send a message and only need to know
when it is sent. Many platforms only listen for incoming messages.
Many platforms have TX and RX but not as parts of one exchange. In
fact, only minority of platforms expect RX after each TX. Btw, what if
some platform sends only and always after each receive? For these
reasons, it is left to the user to tie an incoming RX to some previous
TX, or not.

Regards.
Jassi