From: Guenter Roeck linux@roeck-us.net
[ Upstream commit 012e974501a270d8dfd4ee2039e1fdf7579c907e ]
Rebooting xtensa images loaded with the '-kernel' option in qemu does not work. When executing a reboot command, the qemu session either hangs or experiences an endless sequence of error messages.
Kernel panic - not syncing: Unrecoverable error in exception handler
Reset code jumps to the CPU restart address, but Linux can not recover from there because code and data in the kernel init sections have been discarded and overwritten at this point.
XTFPGA platforms have a means to reset the CPU by writing 0xdead into a specific FPGA IO address. When used in QEMU the kernel image loaded with the '-kernel' option gets restored to its original state allowing the machine to boot successfully.
Use that mechanism to attempt a platform reset. If it does not work, fall back to the existing mechanism.
Signed-off-by: Guenter Roeck linux@roeck-us.net Signed-off-by: Max Filippov jcmvbkbc@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/xtensa/platforms/xtfpga/setup.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/arch/xtensa/platforms/xtfpga/setup.c b/arch/xtensa/platforms/xtfpga/setup.c index 61c5e2c45439..4edccb4d4a5f 100644 --- a/arch/xtensa/platforms/xtfpga/setup.c +++ b/arch/xtensa/platforms/xtfpga/setup.c @@ -50,8 +50,12 @@ void platform_power_off(void)
void platform_restart(void) { - /* Flush and reset the mmu, simulate a processor reset, and - * jump to the reset vector. */ + /* Try software reset first. */ + WRITE_ONCE(*(u32 *)XTFPGA_SWRST_VADDR, 0xdead); + + /* If software reset did not work, flush and reset the mmu, + * simulate a processor reset, and jump to the reset vector. + */ cpu_reset(); /* control never gets here */ }