[PATCH v5 1/7] riscv: Add DMA 64-bit address support

[Bin Meng]

HI Padmarao,

On Fri, Dec 11, 2020 at 4:23 PM Padmarao Begari <padmarao.b at gmail.com> wrote:
>
> Hi Bin,
>
> On Fri, Dec 11, 2020 at 1:22 PM Bin Meng <bmeng.cn at gmail.com> wrote:
>>
>> Hi Padmarao,
>>
>> On Fri, Dec 11, 2020 at 3:10 PM Padmarao Begari <padmarao.b at gmail.com> wrote:
>> >
>> > Hi Bin,
>> >
>> > On Thu, Dec 10, 2020 at 4:11 PM Bin Meng <bmeng.cn at gmail.com> wrote:
>> >>
>> >> Hi Padmarao,
>> >>
>> >> On Thu, Dec 3, 2020 at 4:43 AM Padmarao Begari
>> >> <padmarao.begari at microchip.com> wrote:
>> >> >
>> >> > dma_addr_t holds any valid DMA address. If the DMA API only uses 32/64-bit
>> >> > addresses, dma_addr_t need only be 32/64 bits wide.
>> >> >
>> >> > Signed-off-by: Padmarao Begari <padmarao.begari at microchip.com>
>> >> > Reviewed-by: Anup Patel <anup.patel at wdc.com>
>> >> > ---
>> >> >  arch/riscv/Kconfig             | 4 ++++
>> >> >  arch/riscv/include/asm/types.h | 4 ++++
>> >> >  2 files changed, 8 insertions(+)
>> >> >
>> >> > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
>> >> > index 30b05408b1..55eaee2da6 100644
>> >> > --- a/arch/riscv/Kconfig
>> >> > +++ b/arch/riscv/Kconfig
>> >> > @@ -152,6 +152,10 @@ config 32BIT
>> >> >  config 64BIT
>> >> >         bool
>> >> >
>> >> > +config DMA_ADDR_T_64BIT
>> >> > +       bool
>> >> > +       default y if 64BIT
>> >> > +
>> >> >  config SIFIVE_CLINT
>> >> >         bool
>> >> >         depends on RISCV_MMODE || SPL_RISCV_MMODE
>> >> > diff --git a/arch/riscv/include/asm/types.h b/arch/riscv/include/asm/types.h
>> >> > index 403cf9a48f..b800b2d221 100644
>> >> > --- a/arch/riscv/include/asm/types.h
>> >> > +++ b/arch/riscv/include/asm/types.h
>> >> > @@ -29,7 +29,11 @@ typedef unsigned short umode_t;
>> >> >
>> >> >  #include <stddef.h>
>> >> >
>> >> > +#ifdef CONFIG_DMA_ADDR_T_64BIT
>> >> > +typedef u64 dma_addr_t;
>> >> > +#else
>> >> >  typedef u32 dma_addr_t;
>> >> > +#endif
>> >>
>> >> Why is this patch needed for U-Boot?
>> >>
>> >
>> > Initially this patch was created for the MACB driver dependency and now the MACB driver is not dependent on CONFIG_DMA_ADDR_T_64BIT.
>> > But We created this patch the same as the ARM 64-bit kconfig and the 'CONFIG_DMA_ADDR_T_64BIT' is used when the MMC driver is configured with DMA.
>> >
>>
>> But in U-Boot there is no 64-bit address. The DMA address should be
>> under 4G. Both MACB and MMC driver should work with the 32-bit DMA
>> addresses, no?
>>
>
> We will use 64-bit addresses in the future.

But U-Boot does not generate 64-bit addresses for DMA at present.

> Both MACB and MMC drivers work with 64-bit DMA addresses in the PolarFire SoC.

So I think the patch to enable 64-bit DMA in U-Boot is not necessary.

Regards,
Bin