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

[Padmarao Begari]

Hi Bin,

On Fri, Dec 11, 2020 at 2:57 PM Bin Meng <bmeng.cn at gmail.com> wrote:

> 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.
>
>
PolarFire SoC GEM uses 64-bit DMA not 32-bit DMA

Regards
Padmarao

> > 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
>