On 24 July 2014 22:52, Santosh Shilimkar <santosh.shilimkar@xxxxxx> wrote: > On Thursday 24 July 2014 01:19 PM, Jassi Brar wrote: >> 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 :) >> > Exactly !! > And that was my point. Thanks for echo. > Yeah but if the AP and DSP are within the same package (i.e, the 'pins' can't be used for any other purpose on any board), one might sell it as a mailbox. However, since the mailbox protocol driver would be in userspace, I think it is justified to expose that as GPIO otherwise we'll have to add another interface for userspace to control the DSP. Cheers, Jassi -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
