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

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

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.
> 
>> 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.
> 
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.

> 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