[PATCH 4.9 185/310] powerpc/8xx: fix mpc8xx_get_irq() return on no irq

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Christophe Leroy <christophe.le...@c-s.fr>


[ Upstream commit 3c29b6038828c1f4c9ecbfec14d4fc5e25f1c947 ]

IRQ 0 is a valid HW interrupt. So get_irq() shall return 0 when
there is no irq, instead of returning irq_linear_revmap(... ,0)

Fixes: f2a0bd3753dad ("[POWERPC] 8xx: powerpc port of core CPM PIC")
Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr>
Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 arch/powerpc/sysdev/mpc8xx_pic.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/powerpc/sysdev/mpc8xx_pic.c
+++ b/arch/powerpc/sysdev/mpc8xx_pic.c
@@ -79,7 +79,7 @@ unsigned int mpc8xx_get_irq(void)
        irq = in_be32(&siu_reg->sc_sivec) >> 26;
 
        if (irq == PIC_VEC_SPURRIOUS)
-               irq = 0;
+               return 0;
 
         return irq_linear_revmap(mpc8xx_pic_host, irq);