On Tue, Nov 27, 2018 at 10:50 AM Rick Chen rickchen36@gmail.com wrote:
Anup Patel anup@brainfault.org 於 2018年11月27日 週二 上午11:28寫道：
On Tue, Nov 27, 2018 at 8:50 AM Rick Chen rickchen36@gmail.com wrote:
> Currently, the RISC-V U-Boot is saving a2 register at > CONFIG_SYS_DRAM_BASE in start.S which does not make sense because > there is no information passed by previous booting stage in a2 > register. > > This patch removes redundant a2 store on DRAM base. > > Signed-off-by: Anup Patel anup@brainfault.org > --- > arch/riscv/cpu/start.S | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/arch/riscv/cpu/start.S b/arch/riscv/cpu/start.S index > 704190f946..e4276e8e19 100644 > --- a/arch/riscv/cpu/start.S > +++ b/arch/riscv/cpu/start.S > @@ -38,8 +38,6 @@ _start: > mv s0, a0 > mv s1, a1 > > - li t0, CONFIG_SYS_SDRAM_BASE > - SREG a2, 0(t0) > la t0, trap_entry > #ifdef CONFIG_RISCV_SMODE > csrw stvec, t0 > --
This is weird. I remember these two lines were already removed by Lukas's patch series before? Did not have time to dig out the history though.
Regards, Bin
You are correct, however I removed it again, because I did not want to break Rick's board. He did add a commit to the last pull request that removes these two lines and adjusts his board accordingly, but it is not in the current one.
Hi Likas
Thanks for your explanation.
RIck's commit as below https://www.mail-archive.com/u-boot@lists.denx.de/msg305880.html
When we run U-Boot in S-mode the BBL runs from 0x80000000 so this two lines corrupts BBL instructions.
If this is important for some board then please have it around #ifdef.
Hi Anup
In the discussion as below : https://www.mail-archive.com/u-boot@lists.denx.de/msg305880.html
I try to solve this issue with the aptch [PATCH] riscv: ax25-ae350: Pass dtb address to u-boot with a1 register diff --git a/arch/riscv/cpu/start.S b/arch/riscv/cpu/start.S
li t0, CONFIG_SYS_SDRAM_BASESREG a2, 0(t0)diff --git a/board/AndesTech/ax25-ae350/ax25-ae350.c b/board/AndesTech/ax25-ae350/ax25-ae350.c void *board_fdt_blob_setup(void) {
void **ptr = (void *)CONFIG_SYS_SDRAM_BASE;
void **ptr = (void *)&prior_stage_fdt_address;in the previous pull request.
But Bin do not agree with that I use prior_stage_fdt_address in board_fdt_blob_setup( ) I try to explain why I use it like that way. Then Bin have not any reply in the following mail. Finally I decide to drop this patch in the next pull request.
Hi Bin
How do you think about I recovery this patch to fix this issue ?
Actually, previous booting stage can pass location of FDT stored in flash to U-Boot. U-Boot requires FDT at a DRAM location which it can modify in-place before passing on to Linux kernel so we should relocate the FDT passed by previous booting stage to some board specific DRAM location.
My suggestion is as follows:
Instead of SDRAM_BASE, we can have new board specific config CONFIG_RISCV_PRIOR_FDT_BASE
If CONFIG_RISCV_PRIOR_FDT_BASE is defined/selected by config then in start.S copy-over the FDT from location pointed by "a1" register to location pointed by CONFIG_RISCV_PRIOR_FDT_BASE.
In your board_fdt_blob_setup(), you can safely do: void **ptr = (void *)CONFIG_RISCV_PRIOR_FDT_BASE;
Regards, Anup