[RFC PATCH] arch: riscv: cpu: Add callback to init each core
I am looking for a proper place to add some M-mode code in SPL to configure features of each core as early as possible. Try to start the discussion by sending this RFC.
I tried mach_cpu_init() as the start. And not sure whether I used it correctly, it seems executed only by the core wins lottery in ./arch/riscv/cpu/start.S.
Is there a proper place to add some inits for each core like CSR in section 7.6 in document of U74-MC Core Complex Manual[1].
There are some alternatives to do it such as
a) sending IPI to each cores Have to wait for IPI init for each core. And the boot core have to perform the init by itself and send IPIs to other cores. It might not be straightforward. b) hook callback, (like this patch) c) hard code in ./arch/riscv/cpu/start.c
[1] https://sifive.cdn.prismic.io/sifive/aee0dd4c-d156-496e-a6c4-db0cf54bbe68_si...
Signed-off-by: Green Wan green.wan@sifive.com --- arch/riscv/cpu/start.S | 5 +++++ arch/riscv/lib/spl.c | 4 ++++ board/sifive/unmatched/spl.c | 7 +++++++ 3 files changed, 16 insertions(+)
diff --git a/arch/riscv/cpu/start.S b/arch/riscv/cpu/start.S index 8589509e01..2629f7e4cc 100644 --- a/arch/riscv/cpu/start.S +++ b/arch/riscv/cpu/start.S @@ -102,6 +102,11 @@ call_board_init_f_0: mv a0, sp jal board_init_f_alloc_reserve
+#if CONFIG_IS_ENABLED(RISCV_MMODE) +call_each_cpu_core: + jal mach_cpu_core_init +#endif + /* * Save global data pointer for later. We don't set it here because it * is not initialized yet. diff --git a/arch/riscv/lib/spl.c b/arch/riscv/lib/spl.c index 8baee07bea..e8261d9c19 100644 --- a/arch/riscv/lib/spl.c +++ b/arch/riscv/lib/spl.c @@ -14,6 +14,10 @@
DECLARE_GLOBAL_DATA_PTR;
+__weak void mach_cpu_core_init(void) +{ +} + __weak int spl_board_init_f(void) { return 0; diff --git a/board/sifive/unmatched/spl.c b/board/sifive/unmatched/spl.c index 5e1333b09a..cc466f703a 100644 --- a/board/sifive/unmatched/spl.c +++ b/board/sifive/unmatched/spl.c @@ -22,6 +22,13 @@ #define MODE_SELECT_SD 0xb #define MODE_SELECT_MASK GENMASK(3, 0)
+void mach_cpu_core_init(void) +{ +#if CONFIG_IS_ENABLED(RISCV_MMODE) + asm volatile ("csrwi 0x7c1, 0"); +#endif +} + int spl_board_init_f(void) { int ret;
On Mon, Mar 22, 2021 at 5:23 PM Green Wan green.wan@sifive.com wrote:
I am looking for a proper place to add some M-mode code in SPL to configure features of each core as early as possible. Try to start the discussion by sending this RFC.
I tried mach_cpu_init() as the start. And not sure whether I used it correctly, it seems executed only by the core wins lottery in ./arch/riscv/cpu/start.S.
Is there a proper place to add some inits for each core like CSR in section 7.6 in document of U74-MC Core Complex Manual[1].
There are some alternatives to do it such as
a) sending IPI to each cores Have to wait for IPI init for each core. And the boot core have to perform the init by itself and send IPIs to other cores. It might not be straightforward. b) hook callback, (like this patch) c) hard code in ./arch/riscv/cpu/start.c
[1] https://sifive.cdn.prismic.io/sifive/aee0dd4c-d156-496e-a6c4-db0cf54bbe68_si...
Signed-off-by: Green Wan green.wan@sifive.com
arch/riscv/cpu/start.S | 5 +++++ arch/riscv/lib/spl.c | 4 ++++ board/sifive/unmatched/spl.c | 7 +++++++ 3 files changed, 16 insertions(+)
diff --git a/arch/riscv/cpu/start.S b/arch/riscv/cpu/start.S index 8589509e01..2629f7e4cc 100644 --- a/arch/riscv/cpu/start.S +++ b/arch/riscv/cpu/start.S @@ -102,6 +102,11 @@ call_board_init_f_0: mv a0, sp jal board_init_f_alloc_reserve
+#if CONFIG_IS_ENABLED(RISCV_MMODE) +call_each_cpu_core:
jal mach_cpu_core_init+#endif
Inserting it here potentially corrupts the return value of board_init_f_alloc_reserve(), and you need to insert it after sp is initialized for harts other than the boot hart.
/* * Save global data pointer for later. We don't set it here because it * is not initialized yet.diff --git a/arch/riscv/lib/spl.c b/arch/riscv/lib/spl.c index 8baee07bea..e8261d9c19 100644 --- a/arch/riscv/lib/spl.c +++ b/arch/riscv/lib/spl.c @@ -14,6 +14,10 @@
DECLARE_GLOBAL_DATA_PTR;
+__weak void mach_cpu_core_init(void) +{ +}
__weak int spl_board_init_f(void) { return 0; diff --git a/board/sifive/unmatched/spl.c b/board/sifive/unmatched/spl.c index 5e1333b09a..cc466f703a 100644 --- a/board/sifive/unmatched/spl.c +++ b/board/sifive/unmatched/spl.c @@ -22,6 +22,13 @@ #define MODE_SELECT_SD 0xb #define MODE_SELECT_MASK GENMASK(3, 0)
+void mach_cpu_core_init(void) +{ +#if CONFIG_IS_ENABLED(RISCV_MMODE)
asm volatile ("csrwi 0x7c1, 0");+#endif +}
int spl_board_init_f(void) { int ret; --
Regards, Bin
Hi Bin,
I can move it to the place right after stacks for harts are set up and right before picking up the lottery hart. (like below) How about the function name? Do we come up with a better function name? mach_cpu_core_init() is similar to mach_cpu_init() in include/init.h. It could cause confusion.
116 /* setup stack */ 117 #if CONFIG_IS_ENABLED(SMP) 118 /* tp: hart id */ 119 slli t0, tp, CONFIG_STACK_SIZE_SHIFT 120 sub sp, a0, t0 121 #else 122 mv sp, a0 123 #endif 124
move it here
125 #ifndef CONFIG_XIP 126 /* 127 * Pick hart to initialize global data and run U-Boot. The other harts 128 * wait for initialization to complete. 129 */ 130 la t0, hart_lottery 131 li t1, 1
On Mon, Mar 22, 2021 at 6:04 PM Bin Meng bmeng.cn@gmail.com wrote:
On Mon, Mar 22, 2021 at 5:23 PM Green Wan green.wan@sifive.com wrote:
I am looking for a proper place to add some M-mode code in SPL to configure features of each core as early as possible. Try to start the discussion by sending this RFC.
I tried mach_cpu_init() as the start. And not sure whether I used it correctly, it seems executed only by the core wins lottery in ./arch/riscv/cpu/start.S.
Is there a proper place to add some inits for each core like CSR in section 7.6 in document of U74-MC Core Complex Manual[1].
There are some alternatives to do it such as
a) sending IPI to each cores Have to wait for IPI init for each core. And the boot core have to perform the init by itself and send IPIs to other cores. It might not be straightforward. b) hook callback, (like this patch) c) hard code in ./arch/riscv/cpu/start.c
[1]
https://sifive.cdn.prismic.io/sifive/aee0dd4c-d156-496e-a6c4-db0cf54bbe68_si...
Signed-off-by: Green Wan green.wan@sifive.com
arch/riscv/cpu/start.S | 5 +++++ arch/riscv/lib/spl.c | 4 ++++ board/sifive/unmatched/spl.c | 7 +++++++ 3 files changed, 16 insertions(+)
diff --git a/arch/riscv/cpu/start.S b/arch/riscv/cpu/start.S index 8589509e01..2629f7e4cc 100644 --- a/arch/riscv/cpu/start.S +++ b/arch/riscv/cpu/start.S @@ -102,6 +102,11 @@ call_board_init_f_0: mv a0, sp jal board_init_f_alloc_reserve
+#if CONFIG_IS_ENABLED(RISCV_MMODE) +call_each_cpu_core:
jal mach_cpu_core_init+#endif
Inserting it here potentially corrupts the return value of board_init_f_alloc_reserve(), and you need to insert it after sp is initialized for harts other than the boot hart.
/* * Save global data pointer for later. We don't set it herebecause it
* is not initialized yet.diff --git a/arch/riscv/lib/spl.c b/arch/riscv/lib/spl.c index 8baee07bea..e8261d9c19 100644 --- a/arch/riscv/lib/spl.c +++ b/arch/riscv/lib/spl.c @@ -14,6 +14,10 @@
DECLARE_GLOBAL_DATA_PTR;
+__weak void mach_cpu_core_init(void) +{ +}
__weak int spl_board_init_f(void) { return 0; diff --git a/board/sifive/unmatched/spl.c b/board/sifive/unmatched/spl.c index 5e1333b09a..cc466f703a 100644 --- a/board/sifive/unmatched/spl.c +++ b/board/sifive/unmatched/spl.c @@ -22,6 +22,13 @@ #define MODE_SELECT_SD 0xb #define MODE_SELECT_MASK GENMASK(3, 0)
+void mach_cpu_core_init(void) +{ +#if CONFIG_IS_ENABLED(RISCV_MMODE)
asm volatile ("csrwi 0x7c1, 0");+#endif +}
int spl_board_init_f(void) { int ret; --
Regards, Bin
Hi Green,
On Tue, Mar 23, 2021 at 12:12 PM Green Wan green.wan@sifive.com wrote:
Hi Bin,
I can move it to the place right after stacks for harts are set up and right before picking up the lottery hart. (like below) How about the function name? Do we come up with a better function name? mach_cpu_core_init() is similar to mach_cpu_init() in include/init.h. It could cause confusion.
How about riscv_core_early_init(), or riscv_hart_early_init()?
Regards, Bin
On Tue, Mar 23, 2021 at 1:07 PM Bin Meng bmeng.cn@gmail.com wrote:
Hi Green,
On Tue, Mar 23, 2021 at 12:12 PM Green Wan green.wan@sifive.com wrote:
Hi Bin,
I can move it to the place right after stacks for harts are set up and
right before picking up the lottery hart. (like below) How about the function name? Do we come up with a better function name? mach_cpu_core_init() is similar to mach_cpu_init() in include/init.h. It could cause confusion.
How about riscv_core_early_init(), or riscv_hart_early_init()?
I'll vote for riscv_hart_early_init() and create the v2 patch based on it.
Thanks,
Regards, Bin
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Green Wan