Re: [PATCH v2 4/7] of: configure the platform device dma parameters

[Rob Herring]

On Sat, Apr 19, 2014 at 9:32 AM, 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       |   43 +++++++++++++++++++++++++++++++++++++++++++
>  include/linux/dma-mapping.h |    7 +++++++
>  2 files changed, 50 insertions(+)
>
> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> index 573db15..7e4a43b 100644
> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -187,6 +187,47 @@ 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)
> +{
> +       dma_addr_t dma_addr;
> +       phys_addr_t paddr, size;

A problem with using dma_addr_t and phys_addr_t is that they normally
depend on CONFIG_LPAE, but the address cell sizes are independent of
that. That is why all the memory related functions stick with u64. I
think you would have issues here if you have a platform with sizes of
4GB or more. You need to properly cap the sizes and addresses.

> +       int ret;
> +
> +       /*
> +        * 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) {

Perhaps an error is not the right return for the default case. The
default should probably be dma_addr and paddr equal to 0 and size 4GB.

> +               dev_dbg(dev, "no dma range information to setup\n");
> +               return;
> +       } else {

You don't need the else here.

> +               /* 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
> @@ -217,6 +258,8 @@ static struct platform_device *of_platform_device_create_pdata(
>         dev->dev.coherent_dma_mask = DMA_BIT_MASK(32);
>         if (!dev->dev.dma_mask)
>                 dev->dev.dma_mask = &dev->dev.coherent_dma_mask;

You should move all DMA related setup into of_dma_configure.

> +
> +       of_dma_configure(&dev->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
>
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