Subject: Re: [PATCH V8 2/2] mailbox: introduce ARM SMC based mailbox

From: Florian Fainelli <[email-masked]>
Date: Mon, 23 Sep 2019 19:48:27 -0700

Hi Peng,

On 9/23/2019 6:14 PM, Peng Fan wrote:
> From: Peng Fan <[email-masked]>
> 
> This mailbox driver implements a mailbox which signals transmitted data
> via an ARM smc (secure monitor call) instruction. The mailbox receiver
> is implemented in firmware and can synchronously return data when it
> returns execution to the non-secure world again.
> An asynchronous receive path is not implemented.
> This allows the usage of a mailbox to trigger firmware actions on SoCs
> which either don't have a separate management processor or on which such
> a core is not available. A user of this mailbox could be the SCP
> interface.
> 
> Modified from Andre Przywara's v2 patch
> https://lore.kernel.org/patchwork/patch/812999/
> 
> Cc: Andre Przywara <[email-masked]>
> Signed-off-by: Peng Fan <[email-masked]>
> ---

[snip]

> +typedef unsigned long (smc_mbox_fn)(unsigned int, unsigned long,
> +				    unsigned long, unsigned long,
> +				    unsigned long, unsigned long,
> +				    unsigned long);
> +static smc_mbox_fn *invoke_smc_mbox_fn;

Sorry for spotting this so late, the only thing that concerns me here
with this singleton is if we happen to have both an arm,smc-mbox and
arm,hvc-mbox configured in the system, this would not work. I do not
believe this could be a functional use case, but we should probably
guard against that or better yet, move that into the arm_smc_chan_data
private structure?
-- 
Florian

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