From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756052AbaE2UFd (ORCPT ); Thu, 29 May 2014 16:05:33 -0400 Received: from arroyo.ext.ti.com ([192.94.94.40]:50041 "EHLO arroyo.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752368AbaE2UFb (ORCPT ); Thu, 29 May 2014 16:05:31 -0400 Message-ID: <538792E1.3020500@ti.com> Date: Thu, 29 May 2014 16:04:49 -0400 From: Santosh Shilimkar User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 MIME-Version: 1.0 To: Arnd Bergmann CC: Linus Walleij , Grant Likely , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "devicetree@vger.kernel.org" , Grygorii Strashko , Russell King , Greg Kroah-Hartman , Rob Herring , Catalin Marinas , Olof Johansson Subject: Re: [PATCH v3 4/7] of: configure the platform device dma parameters References: <1398353407-2345-1-git-send-email-santosh.shilimkar@ti.com> <53873F4A.9030303@ti.com> <4755790.VgRQTHz3K1@wuerfel> In-Reply-To: <4755790.VgRQTHz3K1@wuerfel> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 29 May 2014 03:24 PM, Arnd Bergmann wrote: > On Thursday 29 May 2014 10:08:10 Santosh Shilimkar wrote: >> On Thursday 29 May 2014 10:01 AM, Linus Walleij wrote: >>> On Wed, May 28, 2014 at 4:04 PM, Santosh Shilimkar >>> wrote: >>>> On Wednesday 28 May 2014 09:32 AM, Linus Walleij wrote: >>> >>>>>> I suspect what you want is >>>>>> >>>>>> dma-ranges = <0x80000000 0 0x80000000>; >>>>>> >>>>>> to translate dma_addr_t 0x80000000-0xffffffff to phys_addr_t 0x0-0x7fffffff >>>>>> rather than phys_addr_t 0x800000000-0x87fffffff. >>>>> >>>> Interesting. Where does the ROM address space resides on integrator then considering >>>> address 0 is used for DMA. >>> >>> The ROM is at physical address 0x20000000, don't ask me >>> why >>> >>> The RAM is typically at 0x00000000-0x0fffffff, on up to four parallell >>> tiles, i.e. up to four completely independent CPUs are booted off the >>> same ROM and using a set of shared peripherals. >>> >> The reason I asked the question because most of the ARM SOC I came across >> aren't using the RAM phys address 0 and thought was because of boot architecture >> with ROM occupying that address with reset vector starting at address 0. >> >> That was one of the main reason we had description on max_*pfn on ARM w.r.t >> to other acrhes. >> >> Will corner ARM guys to understand bit more about it in some conference > > If this is anything like the versatile express, the reason it works is probably > because there is another microcontroller in the system that does the bootstrap > and is able to load code into RAM before turning on the main CPU. > That make sense now. Thanks for those extra bits. Regards, Santosh