Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751234AbcDPGHm (ORCPT ); Sat, 16 Apr 2016 02:07:42 -0400 Received: from smtprelay.synopsys.com ([198.182.60.111]:45979 "EHLO smtprelay.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751040AbcDPGHl (ORCPT ); Sat, 16 Apr 2016 02:07:41 -0400 Subject: Re: Allocation of frame buffer at a specific memory range or address To: Alexey Brodkin , "dri-devel@lists.freedesktop.org" References: <1460735338.3248.21.camel@synopsys.com> CC: "daniel@ffwll.ch" , "linux-kernel@vger.kernel.org" , "linux-snps-arc@lists.infradead.org" , "airlied@linux.ie" , "devicetree@vger.kernel.org" , Rob Herring From: Vineet Gupta Message-ID: <5711D698.4030606@synopsys.com> Date: Sat, 16 Apr 2016 11:37:20 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: <1460735338.3248.21.camel@synopsys.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.12.197.158] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1087 Lines: 46 On Friday 15 April 2016 09:18 PM, Alexey Brodkin wrote: > And now the question is how to force DRM subsystem or just that driver > to use whatever predefined (say via device tree) location in memory > for data buffer allocation. It seems this is pretty easy to do with DT reserved-memory binding. You need to partition memory into @memory and @reserved-memory. Later can be subdivided into more granular regions and your driver can refer to one of the regions. Something like below (untested) + memory { + device_type = "memory"; + reg = <0x0 0x80000000 0x0 0xA0000000>; + #address-cells = <2>; + #size-cells = <2>; + }; + + reserved-memory { + #address-cells = <2>; + #size-cells = <2>; + ranges; + /* This memory bypasses IOC port */ + fb_reserved@A0000000 { + reg = <0x0 0xA0000000 0x0 0xAF000000>; + #address-cells = <2>; + #size-cells = <2>; + /* no-map; */ + }; + }; + + + fb0: video@12300000 { + memory-region = <&fb_reserved>; + /* ... */ + }; This might also need a DT helper in ARC mm init code. + early_init_fdt_scan_reserved_mem(); HTH, -Vineet