[PATCH v3 0/7] riscv: Correctly handle IPIs already pending upon boot

[Sean Anderson <seanga2@gmail.com>]

On the K210, the prior stage bootloader does not clear IPIs. This presents
a problem, because U-Boot up until this point assumes (with one exception)
that IPIs are cleared when it starts. This series attempts to fix this in a
robust manner, and fix several concurrency bugs I noticed while fixing
these other areas. Heinrich previously submitted a patch addressing part of
this problem in [1].

[1] https://patchwork.ozlabs.org/project/uboot/patch/20200811035648.3284-1-xypron.glpk at gmx.de/

Changes in v3:
- Rename riscv_ipi_init_secondary_hart to dummy_pending_ipi_clear
- Only compile dummy_pending_ipi_clear when SMP is enabled
- Clarify XIP comment
- Updated and expanded most commit messages

Changes in v2:
- Use a valid bit instead of addr to validate IPIs
- Make riscv_ipi_init_secondary_hart static
- Remove fences after amoswaps
- Set gp early with XIP
- Clarify comments regarding tp

Sean Anderson (7):
  Revert "riscv: Clear pending interrupts before enabling IPIs"
  riscv: Match memory barriers between send_ipi_many and handle_ipi
  riscv: Use a valid bit to ignore already-pending IPIs
  riscv: Clear pending IPIs on initialization
  riscv: Consolidate fences into AMOs for available_harts_lock
  riscv: Ensure gp is NULL or points to valid data
  riscv: Add some comments to start.S

 arch/riscv/cpu/cpu.c         | 20 +++++++++++++
 arch/riscv/cpu/start.S       | 58 ++++++++++++++++++++++++++++--------
 arch/riscv/include/asm/smp.h |  7 +++++
 arch/riscv/lib/interrupts.c  |  3 +-
 arch/riscv/lib/smp.c         | 16 +++++++++-
 5 files changed, 89 insertions(+), 15 deletions(-)

-- 
2.28.0