Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933884AbaD3OUA (ORCPT ); Wed, 30 Apr 2014 10:20:00 -0400 Received: from arroyo.ext.ti.com ([192.94.94.40]:55713 "EHLO arroyo.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933820AbaD3OT6 (ORCPT ); Wed, 30 Apr 2014 10:19:58 -0400 Message-ID: <53610663.7070305@ti.com> Date: Wed, 30 Apr 2014 10:19:15 -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> In-Reply-To: <20140429144147.004EEC40992@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 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. Example: static void *loongson_dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle, gfp_t gfp, struct dma_attrs *attrs) { ... /* ignore region specifiers */ gfp &= ~(__GFP_DMA | __GFP_DMA32 | __GFP_HIGHMEM); #ifdef CONFIG_ISA if (dev == NULL) gfp |= __GFP_DMA; else #endif #ifdef CONFIG_ZONE_DMA if (dev->coherent_dma_mask < DMA_BIT_MASK(32)) gfp |= __GFP_DMA; else #endif #ifdef CONFIG_ZONE_DMA32 if (dev->coherent_dma_mask < DMA_BIT_MASK(40)) gfp |= __GFP_DMA32; else #endif ... } Any ways, it can be added later if we have an usecase for that. > Second, while the pfn offset is being determined, I don't see anything > making use of either the base address or size. How is the device > constrained to only getting DMA buffers from within that range? Is the > driver expected to manage that directly? > Drivers don't have to do anything special apart from setting the correct mask. The pfn_offset case, we use DMA_ZONE which takes care of masks already. Size is suppose to be used for dma_mask setup which we discussed in previous threads. Regards, Santosh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/