[U-Boot] [RFC PATCH] ARM: asm: types: Introduce DMA_ADDR_T_64BIT

[Lukasz Majewski <l.majewski@samsung.com>]

Hi Lokesh,

> 
> 
> On Thursday 24 March 2016 02:11 PM, Lukasz Majewski wrote:
> > Hi Lokesh,
> > 
> >> dma_addr_t holds any valid DMA address. If the DMA API only uses
> >> 32-bit addresses, dma_addr_t need only be 32 bits wide.  Bus
> >> addresses, e.g., PCI BARs, may be wider than 32 bits, but drivers
> >> do memory-mapped I/O to ioremapped kernel virtual addresses, so
> >> they don't care about the size of the actual bus addresses.
> >> Also 32 bit ARM systems with LPAE enabled can use 64bit address
> >> space, but DMA still use 32bit address like in case of DRA7 and
> >> Keystone platforms.
> > 
> > I've already stumbled upon this issue...
> > 
> >>
> >> This is inspired from the Linux kernel types implementation[1]
> >>
> >> [1]
> >> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/include/linux/types.h#n142
> >>
> >> Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
> >> ---
> >>  arch/arm/include/asm/types.h | 17 +++++++++++++++--
> >>  1 file changed, 15 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/arch/arm/include/asm/types.h
> >> b/arch/arm/include/asm/types.h index 388058e..d108915 100644
> >> --- a/arch/arm/include/asm/types.h
> >> +++ b/arch/arm/include/asm/types.h
> >> @@ -46,16 +46,29 @@ typedef unsigned long long u64;
> >>  #endif	/* CONFIG_ARM64 */
> >>  
> >>  #ifdef CONFIG_PHYS_64BIT
> >> -typedef unsigned long long dma_addr_t;
> >>  typedef unsigned long long phys_addr_t;
> >>  typedef unsigned long long phys_size_t;
> >>  #else
> >>  /* DMA addresses are 32-bits wide */
> >> -typedef u32 dma_addr_t;
> >>  typedef unsigned long phys_addr_t;
> >>  typedef unsigned long phys_size_t;
> >>  #endif
> >>  
> >> +/*
> >> + * A dma_addr_t can hold any valid DMA address, i.e., any address
> >> returned
> >> + * by the DMA API.
> >> + *
> >> + * If the DMA API only uses 32-bit addresses, dma_addr_t need only
> >> be 32
> >> + * bits wide.  Bus addresses, e.g., PCI BARs, may be wider than 32
> >> bits,
> >> + * but drivers do memory-mapped I/O to ioremapped kernel virtual
> >> addresses,
> >> + * so they don't care about the size of the actual bus addresses.
> >> + */
> >> +#ifdef CONFIG_DMA_ADDR_T_64BIT
> > 
> > Generally this approach is correct, but please pay attention to the
> > CONFIG_PHYS_64BIT.
> > 
> > The actual size of dma_addr_t (64 or 32 bits) is decided by
> > defining or undefining CONFIG_PHYS_64BIT at
> > arch/arm/include/asm/config.h. This is based on the status of
> > CONFIG_ARM64.
> > 
> > To avoid regression we need to take into account status of
> > CONFIG_ARM64 to be sure that CONFIG_DMA_ADDR_T_64BIT is set on
> > ARM64 systems.
> 
> Good point. So we need to select DMA_ADDR_T_64BIT by default for all
> ARM64 systems. I guess the below diff should be sufficient along with
> the $subject patch?
> 
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index e5f57ef..550ecde 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -7,6 +7,10 @@ config SYS_ARCH
>  config ARM64
>  	bool
> 
> +config DMA_ADDR_T_64BIT
> +	bool
> +	default y if ARM64
> +
>  config HAS_VBAR
>          bool
> 
> 
> Thanks and regards,
> Lokesh
> 

Acked-by: Lukasz Majewski <l.majewski@samsung.com>

> > 
> >> +typedef unsigned long long dma_addr_t;
> >> +#else
> >> +typedef u32 dma_addr_t;
> >> +#endif
> >> +
> >>  #endif /* __KERNEL__ */
> >>  
> >>  typedef unsigned long resource_size_t;
> > 
> > 
> > 
> 



-- 
Best regards,

Lukasz Majewski

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