linux-kernel - Re: [PATCH 13/13] mailbox: omap: Remove kernel FIFO message queuing

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Date: Mon, 1 Apr 2024 18:39:20 -0500
From: Hari Nagalla <hnagalla@...com>
To: Andrew Davis <afd@...com>, Jassi Brar <jassisinghbrar@...il.com>,
        Nick
 Saulnier <nsaulnier@...com>,
        Bjorn Andersson <andersson@...nel.org>,
        Mathieu
 Poirier <mathieu.poirier@...aro.org>
CC: <linux-remoteproc@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 13/13] mailbox: omap: Remove kernel FIFO message queuing

On 3/25/24 12:20, Andrew Davis wrote:
> The kernel FIFO queue has a couple issues. The biggest issue is that
> it causes extra latency in a path that can be used in real-time tasks,
> such as communication with real-time remote processors.
> 
> The whole FIFO idea itself looks to be a leftover from before the
> unified mailbox framework. The current mailbox framework expects
> mbox_chan_received_data() to be called with data immediately as it
> arrives. Remove the FIFO and pass the messages to the mailbox
> framework directly.
Yes, this would definitely speed up the message receive path. With RT 
linux, the irq runs in thread context, so that is Ok. But with non-RT 
the whole receive path runs in interrupt context. So, i think it would 
be appropriate to use a threaded_irq()?