Re: [PATCH v2] riscv: enable multi-range memory layout

Wu, Fei
2023-09-14T06:49:06Z

On 9/14/2023 2:05 PM, Heinrich Schuchardt wrote:
>
>
> Am 14. September 2023 07:30:55 MESZ schrieb Fei Wu <fei2.wu@intel.com>:
>> 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
>
> This should move to 7GiB - 1 in your example on riscv64.
>
I'm describing the current implementation of board_get_usable_ram_top()
in ./arch/riscv/cpu/generic/dram.c. Do you mean this function should be
changed? Is the comment about 32bit DMA device still valid?

phys_size_t board_get_usable_ram_top(phys_size_t total_size)
{
/*
* Ensure that we run from first 4GB so that all
* addresses used by U-Boot are 32bit addresses.
*
* This in-turn ensures that 32bit DMA capable
* devices work fine because DMA mapping APIs will
* provide 32bit DMA addresses only.
*/
if (gd->ram_top >= SZ_4G)
return SZ_4G - 1;

return gd->ram_top;
}

>> board_get_usable_ram_top(), but that address is not backed by ram. This
>> patch selects the lowest range instead.
>>
>> Signed-off-by: Fei Wu <fei2.wu@intel.com>
>> ---
>> arch/riscv/cpu/generic/dram.c | 2 +-
>> configs/qemu-riscv64_defconfig | 2 +-
>> configs/qemu-riscv64_smode_defconfig | 2 +-
>> configs/qemu-riscv64_spl_defconfig | 2 +-
>> 4 files changed, 4 insertions(+), 4 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();
>
> Linaro is working on allowing to download a distro image via https and installing from a RAM disk.
>
> We should not artificially reduce the RAM size available for U-Boot by restricting ourselfs to 1 GiB.
>
> We must ensure that ram top is in the upper range.
>
How do they handle the case of >4GB? board_get_usable_ram_top() attached
above always returns <4GB. And it seems like
fdtdec_setup_mem_size_base() cannot ensure the upper one is picked, it
just picks up one, but which one is selected depending on fdt.

Thanks,
Fei.

> Best regards
>
> Heinrich
>
>> }
>>
>> int dram_init_banksize(void)
>> diff --git a/configs/qemu-riscv64_defconfig b/configs/qemu-riscv64_defconfig
>> index 9a8bbef192..aa55317d26 100644
>> --- a/configs/qemu-riscv64_defconfig
>> +++ b/configs/qemu-riscv64_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
>> 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
>> diff --git a/configs/qemu-riscv64_spl_defconfig b/configs/qemu-riscv64_spl_defconfig
>> index bb10145e6e..66dc2a1dd9 100644
>> --- a/configs/qemu-riscv64_spl_defconfig
>> +++ b/configs/qemu-riscv64_spl_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