From mboxrd@z Thu Jan 1 00:00:00 1970 From: Aneesh V Subject: Re: [RFC v3 PATCH 1/3] dt: device tree bindings for DDR memories Date: Fri, 20 Jan 2012 02:26:38 +0530 Message-ID: <4F188386.3080507@ti.com> References: <1326983521-373-1-git-send-email-aneesh@ti.com> <1326983521-373-2-git-send-email-aneesh@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-omap-owner@vger.kernel.org To: Olof Johansson Cc: devicetree-discuss@lists.ozlabs.org, linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Rajendra Nayak , Benoit Cousson List-Id: devicetree@vger.kernel.org Hi Olof, On Friday 20 January 2012 01:01 AM, Olof Johansson wrote: > Hi, > > Sorry for the delay in responding, I know you pinged me about it yesterday. > > On Thu, Jan 19, 2012 at 6:31 AM, Aneesh V wrote: >> device tree bindings for LPDDR2 SDRAM memories compliant >> to JESD209-2 standard. >> >> The 'lpddr2' binding in-turn uses another binding 'lpddr2-timings' >> for specifying the AC timing parameters of the memory device at >> different speed-bins. > > As I just commented on the thread with Mike, I think we would be > better off sticking to embedding a standard JEDEC SPD structure in the > device tree. It's not large (128-256 bytes depending on memory type), > and it's clearly defined and used all over the industry. > > It also has the benefit of reusing parsing code if you ever end up > with a system that uses DIMMs for memory, thus needing to parse the > SPD on said modules. I did mention in the previous thread why SPD doesn't work for us ([1] and [2]). Let me repeat the key points here. 1. I couldn't find an SPD addendum for LPDDR2 from the JEDEC website. 2. This seems to indicate that SPD is not used for LPDDR2 devices. 3. I tried to see if I can fit the DDR3 or DDR2 SPD for our needs. But some of the AC timing parameters needed by our controller are not available in those layouts. I don't see any option other than defining a new binding for LPDDR2. br, Aneesh [1] http://www.mail-archive.com/linux-omap@vger.kernel.org/msg61250.html [2] http://www.mail-archive.com/linux-omap@vger.kernel.org/msg60473.html