MIPS: Loongson 3: Add Loongson-3 SMP support

IPI registers of Loongson-3 include IPI_SET, IPI_CLEAR, IPI_STATUS,
IPI_EN and IPI_MAILBOX_BUF. Each bit of IPI_STATUS indicate a type of
IPI and IPI_EN indicate whether the IPI is enabled. The sender write 1
to IPI_SET bits generate IPIs in IPI_STATUS, and receiver write 1 to
bits of IPI_CLEAR to clear IPIs. IPI_MAILBOX_BUF are used to deliver
more information about IPIs.

Why we change code in arch/mips/loongson/common/setup.c?

If without this change, when SMP configured, system cannot boot since
it hang at printk() in cgroup_init_early(). The root cause is:

console_trylock()
  \-->down_trylock(&console_sem)
    \-->raw_spin_unlock_irqrestore(&sem->lock, flags)
      \-->_raw_spin_unlock_irqrestore()(SMP/UP have different versions)
        \-->__raw_spin_unlock_irqrestore()  (following is the SMP case)
          \-->do_raw_spin_unlock()
            \-->arch_spin_unlock()
              \-->nudge_writes()
                \-->mb()
                  \-->wbflush()
                    \-->__wbflush()

In previous code __wbflush() is initialized in plat_mem_setup(), but
cgroup_init_early() is called before plat_mem_setup(). Therefore, In
this patch we make changes to avoid boot failure.

Signed-off-by: Huacai Chen <chenhc@lemote.com>
Signed-off-by: Hongliang Tao <taohl@lemote.com>
Signed-off-by: Hua Yan <yanh@lemote.com>
Tested-by: Alex Smith <alex.smith@imgtec.com>
Reviewed-by: Alex Smith <alex.smith@imgtec.com>
Cc: John Crispin <john@phrozen.org>
Cc: Steven J. Hill <Steven.Hill@imgtec.com>
Cc: Aurelien Jarno <aurelien@aurel32.net>
Cc: linux-mips@linux-mips.org
Cc: Fuxin Zhang <zhangfx@lemote.com>
Cc: Zhangjin Wu <wuzhangjin@gmail.com>
Patchwork: https://patchwork.linux-mips.org/patch/6638
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/mips/loongson/common/init.c b/arch/mips/loongson/common/init.c
index 81ba3b4a8f30..f37fe5413b73 100644
--- a/arch/mips/loongson/common/init.c
+++ b/arch/mips/loongson/common/init.c
@@ -9,6 +9,7 @@
  */
 
 #include <linux/bootmem.h>
+#include <asm/smp-ops.h>
 
 #include <loongson.h>
 
@@ -33,6 +34,7 @@ void __init prom_init(void)
 
 	/*init the uart base address */
 	prom_init_uart_base();
+	register_smp_ops(&loongson3_smp_ops);
 }
 
 void __init prom_free_prom_memory(void)