[PATCH v2 5/7] ARM: of: introduce common routine for DMA configuration

[Rob Herring]

On Thu, Feb 27, 2014 at 3:17 PM, Santosh Shilimkar
<santosh.shilimkar at ti.com> wrote:
> From: Grygorii Strashko <grygorii.strashko at ti.com>
>
> This patch introduces ARM specific function arm_dt_dma_configure()
> which intended to 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 "dam-coherent" properties if supported. The DMA configuration applied

s/dam/dma/

> by arm_dt_dma_configure() as following:
>  - call of_get_dma_range() and get supported DMA range info
>    (dma_addr, cpu_addr, dma_size);
>  - if "not found" then fill dma_mask as DMA_BIT_MASK(32)
>    (this is default behaviour);
>  - if "failed" then clean up dma_mask (DMA not supported)
>  - if ok then update devices DMA configuration:
>       set dma_mask to (dma_addr + dma_size - 1)
>       set dma_pfn_offset to PFN_DOWN(cpu_addr - dma_addr)
>
> Cc: Russell King <linux at arm.linux.org.uk>
> Cc: Arnd Bergmann <arnd at arndb.de>
> Cc: Olof Johansson <olof at lixom.net>
> Cc: Grant Likely <grant.likely at linaro.org>
> Cc: Rob Herring <robh+dt at kernel.org>
> Signed-off-by: Grygorii Strashko <grygorii.strashko at ti.com>
> Signed-off-by: Santosh Shilimkar <santosh.shilimkar at ti.com>
> ---
>  arch/arm/include/asm/prom.h |    3 +++
>  arch/arm/kernel/devtree.c   |   61 +++++++++++++++++++++++++++++++++++++++++++
>  drivers/of/platform.c       |    5 +++-
>  include/linux/of.h          |    2 +-
>  4 files changed, 69 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/include/asm/prom.h b/arch/arm/include/asm/prom.h
> index b681575..1acb732 100644
> --- a/arch/arm/include/asm/prom.h
> +++ b/arch/arm/include/asm/prom.h
> @@ -11,11 +11,13 @@
>  #ifndef __ASMARM_PROM_H
>  #define __ASMARM_PROM_H
>
> +struct device;
>  #ifdef CONFIG_OF
>
>  extern const struct machine_desc *setup_machine_fdt(unsigned int dt_phys);
>  extern void arm_dt_memblock_reserve(void);
>  extern void __init arm_dt_init_cpu_maps(void);
> +extern void arm_dt_dma_configure(struct device *dev);
>
>  #else /* CONFIG_OF */
>
> @@ -26,6 +28,7 @@ static inline const struct machine_desc *setup_machine_fdt(unsigned int dt_phys)
>
>  static inline void arm_dt_memblock_reserve(void) { }
>  static inline void arm_dt_init_cpu_maps(void) { }
> +static inline void arm_dt_dma_configure(struct device *dev) { }
>
>  #endif /* CONFIG_OF */
>  #endif /* ASMARM_PROM_H */
> diff --git a/arch/arm/kernel/devtree.c b/arch/arm/kernel/devtree.c
> index f751714..926b5dd 100644
> --- a/arch/arm/kernel/devtree.c
> +++ b/arch/arm/kernel/devtree.c
> @@ -18,6 +18,9 @@
>  #include <linux/of_fdt.h>
>  #include <linux/of_irq.h>
>  #include <linux/of_platform.h>
> +#include <linux/of_dma.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/slab.h>
>
>  #include <asm/cputype.h>
>  #include <asm/setup.h>
> @@ -235,3 +238,61 @@ const struct machine_desc * __init setup_machine_fdt(unsigned int dt_phys)
>
>         return mdesc;
>  }
> +
> +void arm_dt_dma_configure(struct device *dev)

The implementation may be ARM specific, but the need for the function
should not be.

> +{
> +       dma_addr_t dma_addr;
> +       phys_addr_t paddr, size;
> +       dma_addr_t dma_mask;
> +       int ret;
> +
> +       /*
> +        * if dma-ranges property doesn't exist - use 32 bits DMA mask
> +        * by default and don't set skip archdata.dma_pfn_offset
> +        */
> +       ret = of_dma_get_range(dev->of_node, &dma_addr, &paddr, &size);
> +       if (ret == -ENODEV) {
> +               dev->coherent_dma_mask = DMA_BIT_MASK(32);
> +               if (!dev->dma_mask)
> +                       dev->dma_mask = &dev->coherent_dma_mask;
> +               return;
> +       }
> +
> +       /* if failed - disable DMA for device */
> +       if (ret < 0) {
> +               dev_err(dev, "failed to configure DMA\n");
> +               return;
> +       }
> +
> +       /* DMA ranges found. Calculate and set dma_pfn_offset */
> +       dev->archdata.dma_pfn_offset = PFN_DOWN(paddr - dma_addr);
> +
> +       /* Configure DMA mask */
> +       dev->dma_mask = kmalloc(sizeof(*dev->dma_mask), GFP_KERNEL);

I don't believe that any ARM platform needs dma_mask to be different
from coherent_dma_mask. I traced the history to when 2 masks were
defined and this was my conclusion. Russell has also recently stated
the same:

https://lkml.org/lkml/2013/8/9/205

> +       if (!dev->dma_mask)
> +               return;
> +
> +       dma_mask = dma_addr + size - 1;
> +
> +       ret = arm_dma_set_mask(dev, dma_mask);
> +       if (ret < 0) {
> +               dev_err(dev, "failed to set DMA mask %#08x\n", dma_mask);
> +               kfree(dev->dma_mask);
> +               dev->dma_mask = NULL;
> +               return;
> +       }
> +
> +       dev_dbg(dev, "dma_pfn_offset(%#08lx) dma_mask(%#016llx)\n",
> +               dev->archdata.dma_pfn_offset, *dev->dma_mask);
> +
> +       if (of_dma_is_coherent(dev->of_node)) {
> +               set_dma_ops(dev, &arm_coherent_dma_ops);

All but this line could be in a common function. So make an arm
version of the function that calls the common function and then does
this. Or perhaps a per arch "get dma ops" function is all that is
needed.

> +               dev_dbg(dev, "device is dma coherent\n");
> +       }
> +
> +       ret = dma_set_coherent_mask(dev, dma_mask);
> +       if (ret < 0) {
> +               dev_err(dev, "failed to set coherent DMA mask %#08x\n",
> +                       dma_mask);
> +       }
> +}
> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> index 404d1da..97d5533 100644
> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -213,10 +213,13 @@ static struct platform_device *of_platform_device_create_pdata(
>
>  #if defined(CONFIG_MICROBLAZE)
>         dev->archdata.dma_mask = 0xffffffffUL;

This should be moved into a microblaze specific version of the function.

> -#endif
> +#elif defined(CONFIG_ARM_LPAE)
> +       arm_dt_dma_configure(&dev->dev);
> +#else
>         dev->dev.coherent_dma_mask = DMA_BIT_MASK(32);
>         if (!dev->dev.dma_mask)
>                 dev->dev.dma_mask = &dev->dev.coherent_dma_mask;
> +#endif
>         dev->dev.bus = &platform_bus_type;
>         dev->dev.platform_data = platform_data;
>
> diff --git a/include/linux/of.h b/include/linux/of.h
> index 70c64ba..a321058 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -136,7 +136,7 @@ static inline unsigned long of_read_ulong(const __be32 *cell, int size)
>         return of_read_number(cell, size);
>  }
>
> -#if defined(CONFIG_SPARC)
> +#if defined(CONFIG_SPARC) || defined(CONFIG_ARM_LPAE)
>  #include <asm/prom.h>

No. The idea here is to get rid of including prom.h.

Rob