Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759682AbaGXSMu (ORCPT ); Thu, 24 Jul 2014 14:12:50 -0400 Received: from mail-qa0-f51.google.com ([209.85.216.51]:46996 "EHLO mail-qa0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759440AbaGXSMs (ORCPT ); Thu, 24 Jul 2014 14:12:48 -0400 MIME-Version: 1.0 In-Reply-To: <53D140EC.9020609@ti.com> References: <1405507426-18992-1-git-send-email-grygorii.strashko@ti.com> <53D140EC.9020609@ti.com> Date: Thu, 24 Jul 2014 23:42:47 +0530 Message-ID: Subject: Re: [PATCH v1] gpio: keystone: add dsp gpio controller driver From: Jassi Brar To: Santosh Shilimkar Cc: Linus Walleij , Grygorii Strashko , Suman Anna , Alexander Shiyan , Alexandre Courbot , "linux-gpio@vger.kernel.org" , ivan.khoronzhuk@ti.com, Muralidharan Karicheri , Rob Herring , Kumar Gala , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 24 July 2014 22:52, Santosh Shilimkar wrote: > On Thursday 24 July 2014 01:19 PM, Jassi Brar wrote: >> On 23 July 2014 20:40, Linus Walleij wrote: >>> On Wed, Jul 16, 2014 at 12:43 PM, Grygorii Strashko >>> wrote: >>> >>>> From: Murali Karicheri >>>> >>>> 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 >>>> Signed-off-by: Grygorii Strashko >>> >>> 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 linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/