From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rob Herring Subject: Re: [PATCH 04/15] ARM: smp_twd: add device tree support Date: Thu, 12 Jan 2012 10:27:21 -0600 Message-ID: <4F0F09E9.3040101@gmail.com> References: <1326287334-1905-1-git-send-email-marc.zyngier@arm.com> <1326287334-1905-5-git-send-email-marc.zyngier@arm.com> <4F0DF9B3.3080804@gmail.com> <4F0EEFEA.1020305@arm.com> <4F0EFF79.8060606@gmail.com> <4F0F03B5.5040300@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4F0F03B5.5040300-5wv7dgnIgG8@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Sender: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org To: Marc Zyngier Cc: devicetree-discuss , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" List-Id: devicetree@vger.kernel.org Adding devicetree-discuss since we are talking bindings... On 01/12/2012 10:00 AM, Marc Zyngier wrote: > On 12/01/12 15:42, Rob Herring wrote: >> On 01/12/2012 08:36 AM, Marc Zyngier wrote: >>> Hi Rob, >>> >>> On 11/01/12 21:05, Rob Herring wrote: >>>> On 01/11/2012 07:08 AM, Marc Zyngier wrote: >>>>> Add bindings to support DT discovery of the ARM Timer Watchdog >>>>> (aka TWD). Only the timer side is converted by this patch. >>>>> >>>>> Cc: Rob Herring >>>>> Signed-off-by: Marc Zyngier >>>>> --- >>>>> Documentation/devicetree/bindings/arm/twd.txt | 29 +++++++++++ >>>>> arch/arm/include/asm/smp_twd.h | 1 + >>>>> arch/arm/kernel/smp_twd.c | 68 ++++++++++++++++++++----- >>>>> 3 files changed, 85 insertions(+), 13 deletions(-) >>>>> create mode 100644 Documentation/devicetree/bindings/arm/twd.txt >>>>> >>>>> diff --git a/Documentation/devicetree/bindings/arm/twd.txt b/Documentation/devicetree/bindings/arm/twd.txt >>>>> new file mode 100644 >>>>> index 0000000..a9d5587 >>>>> --- /dev/null >>>>> +++ b/Documentation/devicetree/bindings/arm/twd.txt >>>>> @@ -0,0 +1,29 @@ >>>>> +* ARM Timer Watchdog >>>>> + >>>>> +ARM 11MP, Cortex-A5 and Cortex-A9 are often associated with a per-core >>>>> +Timer-Watchdog (aka TWD), which provides both a per-cpu local timer >>>>> +and watchdog. >>>>> + >>>>> +The TWD is usually attached to a GIC to deliver its two per-processor >>>>> +interrupts. >>>>> + >>>>> +Main node required properties: >>>>> + >>>>> +- compatible : Should be one of: >>>>> + "arm,cortex-a9-twd" >>>>> + "arm,cortex-a5-twd" >>>>> + "arm,arm11mp-twd" >>>>> + "arm,smp-twd" >>>>> + >>>>> +- interrupts : Two interrupts to each core, the first one for the >>>>> + timer, the second one for the watchdog. >>>>> + >>>>> +- reg : Specify the base address and the size of the TWD. >>>>> + >>>>> +Example: >>>>> + >>>>> + twd@2c000600 { >>>>> + compatible = "arm,arm11mp-twd", "arm,smp-twd"; >>>>> + reg = <0x2c000600 0x100>; >>>>> + interrupts = <1 13 0xf01 1 14 0xf01>; >>>>> + }; >>>> >>>> Why not split the watchdog and timer into 2 nodes? It may not matter >>>> since there is no driver for the timer. If there was, we would have a >>>> problem as you can't match 2 drivers to 1 node. >>> >>> Don't we hit the opposite problem - two nodes with the same address? >> >> No, because the timer is at 0x600-0x61f and the watchdog is at >> 0x620-0x63f. There's no DT requirement on address range start or size. >> >> However, the current watchdog driver includes 0x20 in its register >> offsets, so changing the base address would require a change to the >> driver (but that shouldn't really influence the decision). > > Well, that's what triggered my question. On the other hand, I do not see > any in-tree user of the mpcore_wdt driver, so I suppose we could change > this register offset without too much harm. > > How about something like: > > twd-timer@2c000600 { > compatible = "arm,arm11mp-twd", "arm,smp-twd"; > reg = <0x2c000600 0x20>; > interrupts = <1 13 0xf01>; > }; > > twd-watchdog@2c000620 { > compatible = "arm,arm11mp-wd", "arm,smp-wd"; > reg = <0x2c000620 0x20>; > interrupts = <1 14 0xf01>; BTW, are these really edge triggered? > }; > > I'm not sure about the compatible strings for the watchdog though. Any > better idea? Some reason I did arm,smp-twd and arm-cortex-a9-wdt for highbank.dts which wasn't very consistent. How about *-twd-timer and *-twd-wdt? Probably we should drop the generic "arm-smp-*" versions. Rob