On Tuesday 06 May 2014 04:44 PM, Santosh Shilimkar wrote: > On Tuesday 06 May 2014 05:40 AM, Arnd Bergmann wrote: >> On Monday 05 May 2014 17:47:32 Santosh Shilimkar wrote: >> >>> + dev->coherent_dma_mask = DMA_BIT_MASK(32); >>> + if (!dev->dma_mask) >>> + dev->dma_mask = &dev->coherent_dma_mask; >>> + >>> + /* >>> + * 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 < 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 think there should at least be a comment about why we are computing >> the correct DMA mask here and then ignore that and just use DMA_BIT_MASK(32) >> instead. I understand that Russell and Rob prefer it that way and I'm not >> going to argue, but I find it counterintuitive and I think it deserves >> an explanation in the source code for anybody who is trying to figure >> out how things fit together. >> > In this patch, the dma_mask related code is just moved. We are not calculating > dma_mask either. I was looking for the history of how DMA_BIT_MASK(32) > landed up but couldn't trace it down apart from the fact that the code was > carried from powerPC. May be Rob knows. > > How about below comment ? I didn't delibratly added point about bus > intercepting drivers dma_set_*mask() call etc. > > /* > * Set default dma-mask to 32 bit. Drivers are expected to setup > * the correct supported dma_mask. > */ > + dev->coherent_dma_mask = DMA_BIT_MASK(32); > + if (!dev->dma_mask) > + dev->dma_mask = &dev->coherent_dma_mask; > Updated patch below for records. >From 591c1ee465ce5372385dbc41e7d3e36cbb477bd8 Mon Sep 17 00:00:00 2001 From: Santosh Shilimkar <santosh.shilimkar@xxxxxx> Date: Thu, 24 Apr 2014 11:30:04 -0400 Subject: [PATCH v3 4/7] of: configure the platform device dma parameters 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: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Linus Walleij <linus.walleij@xxxxxxxxxx> Reviewed-by: Rob Herring <robh@xxxxxxxxxx> Signed-off-by: Grygorii Strashko <grygorii.strashko@xxxxxx> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@xxxxxx> --- drivers/of/platform.c | 65 +++++++++++++++++++++++++++++++++++++++---- include/linux/dma-mapping.h | 7 +++++ 2 files changed, 66 insertions(+), 6 deletions(-) diff --git a/drivers/of/platform.c b/drivers/of/platform.c index 404d1da..91fa983 100644 --- a/drivers/of/platform.c +++ b/drivers/of/platform.c @@ -187,6 +187,64 @@ 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 platform_device *pdev) +{ + u64 dma_addr, paddr, size; + int ret; + struct device *dev = &pdev->dev; + +#if defined(CONFIG_MICROBLAZE) + pdev->archdata.dma_mask = 0xffffffffUL; +#endif + + /* + * Set default dma-mask to 32 bit. Drivers are expected to setup + * the correct supported dma_mask. + */ + dev->coherent_dma_mask = DMA_BIT_MASK(32); + + /* + * Set it to coherent_dma_mask by default if the architecture + * code has not set it. + */ + 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 < 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); +} + +/** * of_platform_device_create_pdata - Alloc, initialize and register an of_device * @np: pointer to node to create device for * @bus_id: name to assign device @@ -211,12 +269,7 @@ static struct platform_device *of_platform_device_create_pdata( if (!dev) return NULL; -#if defined(CONFIG_MICROBLAZE) - dev->archdata.dma_mask = 0xffffffffUL; -#endif - dev->dev.coherent_dma_mask = DMA_BIT_MASK(32); - if (!dev->dev.dma_mask) - dev->dev.dma_mask = &dev->dev.coherent_dma_mask; + of_dma_configure(dev); dev->dev.bus = &platform_bus_type; dev->dev.platform_data = platform_data; diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index fd4aee2..c7d9b1b 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -123,6 +123,13 @@ static inline int dma_coerce_mask_and_coherent(struct device *dev, u64 mask) extern u64 dma_get_required_mask(struct device *dev); +#ifndef set_arch_dma_coherent_ops +static inline int set_arch_dma_coherent_ops(struct device *dev) +{ + return 0; +} +#endif + static inline unsigned int dma_get_max_seg_size(struct device *dev) { return dev->dma_parms ? dev->dma_parms->max_segment_size : 65536; -- 1.7.9.5 -- 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