On Thursday 01 May 2014 09:12 AM, Grant Likely wrote: > On Wed, 30 Apr 2014 10:19:15 -0400, Santosh Shilimkar <santosh.shilimkar@xxxxxx> 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 <santosh.shilimkar@xxxxxx> 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 <gregkh@xxxxxxxxxxxxxxxxxxx> >>>> Cc: Russell King <linux@xxxxxxxxxxxxxxxx> >>>> Cc: Arnd Bergmann <arnd@xxxxxxxx> >>>> Cc: Olof Johansson <olof@xxxxxxxxx> >>>> Cc: Grant Likely <grant.likely@xxxxxxxxxx> >>>> Cc: Rob Herring <robh+dt@xxxxxxxxxx> >>>> Cc: Catalin Marinas <catalin.marinas@xxxxxxx> >>>> Cc: Linus Walleij <linus.walleij@xxxxxxxxxx> >>>> Signed-off-by: Grygorii Strashko <grygorii.strashko@xxxxxx> >>>> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@xxxxxx> >>>> --- >>>> 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 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html