Re: [PATCH v1] gpio: keystone: add dsp gpio controller driver

[Jassi Brar <jaswinder.singh@xxxxxxxxxx>]

On 23 July 2014 20:40, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:
> On Wed, Jul 16, 2014 at 12:43 PM, Grygorii Strashko
> <grygorii.strashko@xxxxxx> wrote:
>
>> From: Murali Karicheri <m-karicheri2@xxxxxx>
>>
>> On Keystone SOCs, ARM host can send interrupts to DSP cores using the
>> DSP GPIO controller IP. Each DSP GPIO controller provides 28 IRQ signals for
>> each DSP core. This is one of the component used by the IPC mechanism used
>> on Keystone SOCs.
>>
>> Keystone 2 DSP GPIO controller has specific features:
>> - each GPIO can be configured only as output pin;
>> - setting GPIO value to 1 causes IRQ generation on target DSP core;
>> - reading pin value returns 0 - if IRQ was handled or 1 - IRQ is still
>>   pending.
>>
>> Signed-off-by: Murali Karicheri <m-karicheri2@xxxxxx>
>> Signed-off-by: Grygorii Strashko <grygorii.strashko@xxxxxx>
>
> Pardon me. How is this GENERAL PURPOSE Input/Output?
>
> It seems very very much SPECIAL PURPOSE to me, it's like
> you're just shoehorning some IPC mechanism into the GPIO
> subsystem, and this may be because the datasheet calls it
> GPIO when it's not.
>
> What other stuff than DSP is connected to these lines, and is it
> really even external lines? Aren't these just polysilicon rails
> pretty much hammered to be used by the DSP and nothing else.
>
> What is the difference between this and a mailbox IRQ line
> and the kind of stuff handled by drivers/mailbox?
>
> I'd like Suman and Jassi to have a look at this to see if it's
> actually a mailbox before we proceed.
>
The controller seems like most others, only incapable of reading
signals (output only).
 The userspace driving those signals to communicate with a DSP isn't
enough to call it a mailbox usecase, because on a different board the
userspace may drive those signals to control LEDs :)

Cheers,
Jassi
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