From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754610AbaEANQz (ORCPT ); Thu, 1 May 2014 09:16:55 -0400 Received: from arroyo.ext.ti.com ([192.94.94.40]:54904 "EHLO arroyo.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752711AbaEANQx (ORCPT ); Thu, 1 May 2014 09:16:53 -0400 Message-ID: <5362491C.9020402@ti.com> Date: Thu, 1 May 2014 09:16:12 -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: Grant Likely , CC: , , Greg Kroah-Hartman , Russell King , Arnd Bergmann , Olof Johansson , Rob Herring , Catalin Marinas , Linus Walleij , Grygorii Strashko Subject: Re: [PATCH v3 4/7] of: configure the platform device dma parameters References: <1398353407-2345-1-git-send-email-santosh.shilimkar@ti.com> <1398353407-2345-5-git-send-email-santosh.shilimkar@ti.com> <20140429144147.004EEC40992@trevor.secretlab.ca> <53610663.7070305@ti.com> <20140501131210.CCC13C409DA@trevor.secretlab.ca> In-Reply-To: <20140501131210.CCC13C409DA@trevor.secretlab.ca> 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 01 May 2014 09:12 AM, Grant Likely wrote: > On Wed, 30 Apr 2014 10:19:15 -0400, Santosh Shilimkar wrote: >> Hi Grant, >> >> On Tuesday 29 April 2014 10:41 AM, Grant Likely wrote: >>> On Thu, 24 Apr 2014 11:30:04 -0400, Santosh Shilimkar wrote: >>>> Retrieve DMA configuration from DT and setup platform device's DMA >>>> parameters. The DMA configuration in DT has to be specified using >>>> "dma-ranges" and "dma-coherent" properties if supported. >>>> >>>> We setup dma_pfn_offset using "dma-ranges" and dma_coherent_ops >>>> using "dma-coherent" device tree properties. >>>> >>>> The set_arch_dma_coherent_ops macro has to be defined by arch if >>>> it supports coherent dma_ops. Otherwise, set_arch_dma_coherent_ops() is >>>> declared as nop. >>>> >>>> Cc: Greg Kroah-Hartman >>>> Cc: Russell King >>>> Cc: Arnd Bergmann >>>> Cc: Olof Johansson >>>> Cc: Grant Likely >>>> Cc: Rob Herring >>>> Cc: Catalin Marinas >>>> Cc: Linus Walleij >>>> Signed-off-by: Grygorii Strashko >>>> Signed-off-by: Santosh Shilimkar >>>> --- >>>> drivers/of/platform.c | 48 ++++++++++++++++++++++++++++++++++++++++--- >>>> include/linux/dma-mapping.h | 7 +++++++ >>>> 2 files changed, 52 insertions(+), 3 deletions(-) >>>> >>>> diff --git a/drivers/of/platform.c b/drivers/of/platform.c >>>> index 48de98f..270c0b9 100644 >>>> --- a/drivers/of/platform.c >>>> +++ b/drivers/of/platform.c >>>> @@ -187,6 +187,50 @@ struct platform_device *of_device_alloc(struct device_node *np, >>>> EXPORT_SYMBOL(of_device_alloc); >>>> >>>> /** >>>> + * of_dma_configure - Setup DMA configuration >>>> + * @dev: Device to apply DMA configuration >>>> + * >>>> + * Try to get devices's DMA configuration from DT and update it >>>> + * accordingly. >>>> + * >>>> + * In case if platform code need to use own special DMA configuration,it >>>> + * can use Platform bus notifier and handle BUS_NOTIFY_ADD_DEVICE event >>>> + * to fix up DMA configuration. >>>> + */ >>>> +static void of_dma_configure(struct device *dev) >>>> +{ >>>> + u64 dma_addr, paddr, size; >>>> + int ret; >>>> + >>>> + dev->coherent_dma_mask = DMA_BIT_MASK(32); >>>> + if (!dev->dma_mask) >>>> + dev->dma_mask = &dev->coherent_dma_mask; >>>> + >>>> + /* >>>> + * if dma-coherent property exist, call arch hook to setup >>>> + * dma coherent operations. >>>> + */ >>>> + if (of_dma_is_coherent(dev->of_node)) { >>>> + set_arch_dma_coherent_ops(dev); >>>> + dev_dbg(dev, "device is dma coherent\n"); >>>> + } >>>> + >>>> + /* >>>> + * if dma-ranges property doesn't exist - just return else >>>> + * setup the dma offset >>>> + */ >>>> + ret = of_dma_get_range(dev->of_node, &dma_addr, &paddr, &size); >>>> + if ((ret == -ENODEV) || (ret < 0)) { >>>> + dev_dbg(dev, "no dma range information to setup\n"); >>>> + return; >>>> + } >>>> + >>>> + /* DMA ranges found. Calculate and set dma_pfn_offset */ >>>> + dev->dma_pfn_offset = PFN_DOWN(paddr - dma_addr); >>>> + dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", dev->dma_pfn_offset); >>> >>> I've got two concerns here. of_dma_get_range() retrieves only the first >>> tuple from the dma-ranges property, but it is perfectly valid for >>> dma-ranges to contain multiple tuples. How should we handle it if a >>> device has multiple ranges it can DMA from? >>> >> >> We've not found any cases in current Linux where more than one dma-ranges >> would be used. Moreover, The MM (definitely for ARM) isn't supported such >> cases at all (if i understand everything right). >> - there are only one arm_dma_pfn_limit >> - there is only one MM zone is used for ARM >> - some arches like x86,mips can support 2 zones (per arch - not per device or bus) >> DMA & DMA32, but they configured once and forever per arch. > > Okay. If anyone ever does implement multiple ranges then this code will > need to be revisited. > Sure. Thanks for the review !! Regards, Santosh