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riscv: Use a valid bit to ignore already-pending IPIs

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Some IPIs may already be pending when U-Boot is started. This could be a
problem if a secondary hart tries to handle an IPI before the boot hart has
initialized the IPI device.

To be specific, the Kendryte K210 ROM-based bootloader does not clear IPIs
before passing control to U-Boot. Without this patch, the secondary hart
jumps to address 0x0 as soon as it enters secondary_hart_loop, and then
hangs in its trap handler.

This commit introduces a valid bit so secondary harts know when and IPI
originates from U-Boot, and it is safe to use the IPI API. The valid bit is
initialized to 0 by board_init_f_init_reserve. Before this, secondary harts
wait in wait_for_gd_init.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Bin Meng <bin.meng@windriver.com>
Reviewed-by: Rick Chen <rick@andestech.com>
Reviewed-by: Leo Liang <ycliang@andestech.com>
This commit is contained in:
Sean Anderson 2020-09-21 07:51:37 -04:00 committed by Andes
parent d4990a4648
commit f760c9a1fd
2 changed files with 21 additions and 2 deletions
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7
arch/riscv/include/asm/smp.h
View File

@ -18,14 +18,21 @@
* IPI data structure. The hart ID is inserted by the hart handling the IPI and
* calling the function.
*
* @valid is used to determine whether a sent IPI originated from U-Boot. It is
* initialized to zero by board_init_f_alloc_reserve. When U-Boot sends its
* first IPI, it is set to 1. This prevents already-pending IPIs not sent by
* U-Boot from being taken.
*
* @addr: Address of function
* @arg0: First argument of function
* @arg1: Second argument of function
* @valid: Whether this IPI is valid
*/
struct ipi_data {
ulong addr;
ulong arg0;
ulong arg1;
unsigned int valid;
};
/**

16
arch/riscv/lib/smp.c
View File

@ -54,7 +54,13 @@ static int send_ipi_many(struct ipi_data *ipi, int wait)
gd->arch.ipi[reg].arg0 = ipi->arg0;
gd->arch.ipi[reg].arg1 = ipi->arg1;
__smp_mb();
/*
* Ensure valid only becomes set when the IPI parameters are
* set. An IPI may already be pending on other harts, so we
* need a way to signal that the IPI device has been
* initialized, and that it is ok to call the function.
*/
__smp_store_release(&gd->arch.ipi[reg].valid, 1);
ret = riscv_send_ipi(reg);
if (ret) {
@ -83,7 +89,13 @@ void handle_ipi(ulong hart)
if (hart >= CONFIG_NR_CPUS)
return;
__smp_mb();
/*
* If valid is not set, then U-Boot has not requested the IPI. The
* IPI device may not be initialized, so all we can do is wait for
* U-Boot to initialize it and send an IPI
*/
if (!__smp_load_acquire(&gd->arch.ipi[hart].valid))
return;
smp_function = (void (*)(ulong, ulong, ulong))gd->arch.ipi[hart].addr;
invalidate_icache_all();