linux-kernel - Re: [RFC] dt-bindings: mailbox: add doorbell support to ARM MHU

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20200529040758.kneg2j4n3gxh2rfv@vireshk-i7>
Date:   Fri, 29 May 2020 09:37:58 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Jassi Brar <jassisinghbrar@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        Frank Rowand <frowand.list@...il.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        linux-arm-kernel@...ts.infradead.org,
        Sudeep Holla <sudeep.holla@....com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC] dt-bindings: mailbox: add doorbell support to ARM MHU

On 28-05-20, 13:20, Rob Herring wrote:
> Whether Linux 
> requires serializing mailbox accesses is a separate issue. On that side, 
> it seems silly to not allow driving the h/w in the most efficient way 
> possible.

That's exactly what we are trying to say. The hardware allows us to
write all 32 bits in parallel, without any hardware issues, why
shouldn't we do that ? The delay (which Sudeep will find out, he is
facing issues with hardware access because of lockdown right now)
which may be small in transmitting across a mailbox becomes
significant because of the fact that it happens synchronously and the
receiver will send some sort of acknowledgement (and that depends on
the firmware there) and the kernel needs to wait for it, while the
kernel doesn't really need to. There is no reason IMHO for being
inefficient here while we can do better.

-- 
viresh