MIPS: Malta: Register UP SMP ops if all else fails

If we fail to register any real SMP implementations, fall back to
registering the dummy UP implementation. Otherwise when we build an SMP
kernel & run it on a system where the SMP implementations fail to probe
(eg. QEMU) the kernel will perform a NULL dereference attempting to call
mp_ops->smp_setup() from plat_smp_setup().

Notably this fixes booting kernels with CPS SMP enabled on QEMU, which
doesn't currently implement the CM, CPC or GIC.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Rob Herring <robh@kernel.org>
Cc: linux-kernel@vger.kernel.org
Cc: Markos Chandras <markos.chandras@imgtec.com>
Patchwork: https://patchwork.linux-mips.org/patch/11223/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 703438a..9322d26 100644 (file)
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -425,6 +425,7 @@ config MIPS_MALTA
        select MIPS_L1_CACHE_SHIFT_6
        select PCI_GT64XXX_PCI0
        select MIPS_MSC
+       select SMP_UP if SMP
        select SWAP_IO_SPACE
        select SYS_HAS_CPU_MIPS32_R1
        select SYS_HAS_CPU_MIPS32_R2

diff --git a/arch/mips/mti-malta/malta-init.c b/arch/mips/mti-malta/malta-init.c
index 53c2478..571148c 100644 (file)
--- a/arch/mips/mti-malta/malta-init.c
+++ b/arch/mips/mti-malta/malta-init.c
@@ -302,6 +302,7 @@ mips_pci_controller:
                return;
        if (!register_vsmp_smp_ops())
                return;
+       register_up_smp_ops();
 }
 
 void platform_early_l2_init(void)