From: Stephen Warren <swarren@wwwdotorg.org>
To: Jassi Brar <jassisinghbrar@gmail.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Joseph Lo <josephl@nvidia.com>
Subject: Re: Using the mailbox subsystem for plain doorbells?
Date: Tue, 10 May 2016 09:56:58 -0600 [thread overview]
Message-ID: <573204CA.8080808@wwwdotorg.org> (raw)
In-Reply-To: <CABb+yY1Oss376KOgDcpDAHauamECn9r4NA5x=KL3y3UWMh9C2A@mail.gmail.com>
On 05/09/2016 09:29 PM, Jassi Brar wrote:
> On Tue, May 10, 2016 at 5:15 AM, Stephen Warren <swarren@wwwdotorg.org> wrote:
>> Jassi,
>>
>> Does the HW described below sound like something that should be represented
>> using the Linux kernel's mailbox subsystem, and related DT bindings? I think
>> the existing drivers/mailbox/pcc.c is similar, but wanted to double-check.
>>
>> We have some HW that literally just allows a SW-generated interrupt to be
>> generated by our main CPU complex to an auxiliary CPU, and likewise a
>> different interrupt can be generated in the opposite direction. There's no
>> ability to transfer any data; just an IRQ is generated. Our current mailbox
>> implementation just handles IRQ generation/reception so struct
>> mbox_chan_ops.send_data completely ignores the data parameter, and our IRQ
>> handler "receives" hard-coded NULL messages when the IRQ fires. Higher level
>> protocol code (using shared memory along with the plain-IRQ mbox channels)
>> is outside the mailbox driver.
>>
>> Does that fit the mailbox subsystem?
>>
> From the sound of it, yes.
Good to know, thanks.
> Some controllers need a mask/list of destination cpus, to which the
> irq is raised, written to some 'data' register. You too probably need
> to program the destination "id" in the controller? Maybe that should
> be done in send_data().
In this case, each mailbox communicates with a different remote CPU, and
there's a separate register to communicate with each remote CPU. So,
send_data() completely ignores the data parameter since everything is
derived from the mailbox's identity.
next prev parent reply other threads:[~2016-05-10 15:57 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-09 23:45 Using the mailbox subsystem for plain doorbells? Stephen Warren
2016-05-10 3:29 ` Jassi Brar
2016-05-10 15:56 ` Stephen Warren [this message]
2016-05-10 16:10 ` Jassi Brar
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