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

[Lokesh Vutla]

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 at 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

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