Re: [PATCH] riscv: enable multi-range memory layout

["Wu, Fei" <fei2.wu@intel.com>]

On 9/5/2023 6:09 PM, Fei Wu wrote:
> In order to enable PCIe passthrough on qemu riscv, the physical memory
> range between 3GB and 4GB is reserved. Therefore if guest has 4GB ram,
> two ranges are created as [2G, 3G) and [4G, 7G), currently u-boot sets
> ram_top to 4G - 1 if the gd->ram_top is above 4G in
> board_get_usable_ram_top(), but that address is not backed by ram. This
> patch selects the lowest range instead.
> 
I think multi-range memory layout is a common requirement, PCIe
passthrough happens to be the first one to require it. Could anyone
please take a look at this patch and give your comments?

Thanks,
Fei.

> Signed-off-by: Fei Wu <fei2.wu@intel.com>
> ---
>  arch/riscv/cpu/generic/dram.c        | 2 +-
>  configs/qemu-riscv64_smode_defconfig | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/riscv/cpu/generic/dram.c b/arch/riscv/cpu/generic/dram.c
> index 44e11bd56c..fb53a57b4e 100644
> --- a/arch/riscv/cpu/generic/dram.c
> +++ b/arch/riscv/cpu/generic/dram.c
> @@ -13,7 +13,7 @@ DECLARE_GLOBAL_DATA_PTR;
>  
>  int dram_init(void)
>  {
> -	return fdtdec_setup_mem_size_base();
> +	return fdtdec_setup_mem_size_base_lowest();
>  }
>  
>  int dram_init_banksize(void)
> diff --git a/configs/qemu-riscv64_smode_defconfig b/configs/qemu-riscv64_smode_defconfig
> index 1d0f021ade..de08a49dab 100644
> --- a/configs/qemu-riscv64_smode_defconfig
> +++ b/configs/qemu-riscv64_smode_defconfig
> @@ -1,6 +1,6 @@
>  CONFIG_RISCV=y
>  CONFIG_SYS_MALLOC_LEN=0x800000
> -CONFIG_NR_DRAM_BANKS=1
> +CONFIG_NR_DRAM_BANKS=2
>  CONFIG_HAS_CUSTOM_SYS_INIT_SP_ADDR=y
>  CONFIG_CUSTOM_SYS_INIT_SP_ADDR=0x80200000
>  CONFIG_ENV_SIZE=0x20000