From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jon Hunter Subject: Re: [PATCH v7 5/5] ARM: OMAP: gpmc: add DT bindings for GPMC timings and NAND Date: Thu, 6 Dec 2012 10:19:55 -0600 Message-ID: <50C0C5AB.3030201@ti.com> References: <1354734571-10774-1-git-send-email-zonque@gmail.com> <1354734571-10774-6-git-send-email-zonque@gmail.com> <20121205222232.67B2B3E0E22@localhost> <50BFCBCC.6030706@ti.com> <20121205232426.BAD573E0E22@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20121205232426.BAD573E0E22@localhost> 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" To: Grant Likely Cc: x0148406-l0cyMroinI0@public.gmane.org, devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, nsekhar-l0cyMroinI0@public.gmane.org, rob.herring-bsGFqQB8/DxBDgjK7y7TUQ@public.gmane.org, linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: devicetree@vger.kernel.org On 12/05/2012 05:24 PM, Grant Likely wrote: > On Wed, 5 Dec 2012 16:33:48 -0600, Jon Hunter wrote: >> Hi Grant, >> >> On 12/05/2012 04:22 PM, Grant Likely wrote: >>> On Wed, 5 Dec 2012 20:09:31 +0100, Daniel Mack wrote: >>>> This patch adds basic DT bindings for OMAP GPMC. >>>> >>>> The actual peripherals are instantiated from child nodes within the GPMC >>>> node, and the only type of device that is currently supported is NAND. >>>> >>>> Code was added to parse the generic GPMC timing parameters and some >>>> documentation with examples on how to use them. >>>> >>>> Successfully tested on an AM33xx board. >>>> >>>> Signed-off-by: Daniel Mack >>>> --- >>>> Documentation/devicetree/bindings/bus/ti-gpmc.txt | 77 ++++++++++ >>>> .../devicetree/bindings/mtd/gpmc-nand.txt | 76 +++++++++ >>>> arch/arm/mach-omap2/gpmc.c | 171 ++++++++++++++++++++- >>>> 3 files changed, 323 insertions(+), 1 deletion(-) >>>> create mode 100644 Documentation/devicetree/bindings/bus/ti-gpmc.txt >>>> create mode 100644 Documentation/devicetree/bindings/mtd/gpmc-nand.txt >>>> >>>> diff --git a/Documentation/devicetree/bindings/bus/ti-gpmc.txt b/Documentation/devicetree/bindings/bus/ti-gpmc.txt >>>> new file mode 100644 >>>> index 0000000..7d2a645 >>>> --- /dev/null >>>> +++ b/Documentation/devicetree/bindings/bus/ti-gpmc.txt >>>> @@ -0,0 +1,77 @@ >>>> +Device tree bindings for OMAP general purpose memory controllers (GPMC) >>>> + >>>> +The actual devices are instantiated from the child nodes of a GPMC node. >>>> + >>>> +Required properties: >>>> + >>>> + - compatible: Should be set to "ti,gpmc" >>> >>> Please, be specific. Use something like "ti,am3340-gpmc" or >>> "ti,omap3430-gpmc". The compatible property is a list so that new >>> devices can claim compatibility with old. Compatible strings that are >>> overly generic are a pet-peave of mine. >> >> We aim to use the binding for omap2,3,4,5 as well as the am33xx devices >> (which are omap based). Would it be sufficient to have "ti,omap2-gpmc" >> implying all omap2+ based devices or should we have a compatible string >> for each device supported? > > Are they each register-level compatible with one another? They are not 100% register compatible. There are a couple fields in the binding that are only applicable to OMAP3+ devices. > The general recommended approach here is to make subsequent silicon > claim compatibility with the first compatible implementation. > > So, for an am3358 board: > compatible = "ti,am3358-gpmc", "ti,omap2420-gpmc"; > > Essentially, what this means is that "ti,omap2420-gpmc" is the generic > value instead of "omap2-gpmc". The reason for this is so that the value > is anchored against a specific implementation, and not against something > completely imaginary or idealized. If a newer version isn't quite > compatible with the omap2420-gpmc, then it can drop the compatible claim > and the driver really should be told about the new device. Ok, gotcha! I will do a register comparison and may be recommend to Daniel which compatible strings we will need. Thanks! Jon