Hi, On 07/24/2014 01:12 PM, Jassi Brar wrote: > 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. If all these pins or a group of pins are collectively being used to denote a message to the DSP, then I can see the argument for this being a mailbox platform driver. It then probably would need to be supplemented by some other protocol driver to expose the necessary functionality to userspace. Otherwise, I agree with Jassi in general. That said, having two different drivers for different GPIO IP instances within the same SoC doesn't make sense. There should be a single driver for all the GPIO IPs in keystone, output/input only are properties of the instance and the driver should handle that IMHO. regards Suman -- 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
