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

[Wu, Fei]

On 10/9/2023 6:04 PM, Wu, Fei wrote:
> On 9/14/2023 2:05 PM, Heinrich Schuchardt wrote:
>>
>>
>> Am 14. September 2023 07:30:55 MESZ schrieb Fei Wu <fei2.wu at 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.
>>
>>> 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 at 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.
>>
> It's okay if we don't do this installation and pcie passthrough together
> on risc-v, nothing is changed if there is single-range memory, 1GB is
> large enough for other cases.
> 
So far there are the following methods:

1. use fdtdec_setup_mem_size_base_lowest as this one. This is a change
to generic riscv iff the multi-range memory is applied, which is not the
case for all the current riscv boards. If there are such memory layout
riscv boards in the future, it can have its specialized version.

2. specialize dram_init() for qemu-riscv, it limits the impact only to
qemu-riscv, even if there is a need to download image, it doesn't need
to enable pcie-passthru at the same time, so no impact from this
perspective, the drawback is that qemu cannot reuse the generic logic.

3. a complete solution for multi-range memory layout to select the
largest range for all architectures.

Are #1 or #2 acceptable at this stage? If we go #3, can someone help me
drive this together to reduce the email ping-pongs?

Thanks,
Fei.


>> 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.
>>
> You mentioned a generic solution for all architectures in another
> thread, it looks not trivial for me with little background on u-boot,
> e.g. something is confusing to me, when a board should define
> CFG_SYS_SDRAM_BASE, what happens if gd->ram_base != CFG_SYS_SDRAM_BASE,
> I'm not sure if you or anyone can help drive this together. btw, the
> good part of this patch is that it doesn't change the semantics of
> ram_base, and the best choice is the largest range, the upper range
> might not.
> 
> 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
>