ARM: 7846/1: Update SMP_ON_UP code to detect A9MPCore with 1 CPU devices

The generic code is well equipped to differentiate between
SMP and UP configurations.However, there are some devices which
use Cortex-A9 MP core IP with 1 CPU as configuration. To let
these SOCs to co-exist in a CONFIG_SMP=y build by leveraging
the SMP_ON_UP support, we need to additionally check the
number the cores in Cortex-A9 MPCore configuration. Without
such a check in place, the startup code tries to execute
ALT_SMP() set of instructions which lead to CPU faults.

The issue was spotted on TI's Aegis device and this patch
makes now the device work with omap2plus_defconfig which
enables SMP by default. The change is kept limited to only
Cortex-A9 MPCore detection code.

Note that if any future SoC *does* use 0x0 as the PERIPH_BASE, then
the SCU address check code needs to be #ifdef'd for for the Aegis
platform.
Acked-by: Sricharan R <r.sricharan@ti.com>
Signed-off-by: Vaibhav Bedia <vaibhav.bedia@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/kernel/head.S

@@ -487,7 +487,26 @@ __fixup_smp:
 	mrc	p15, 0, r0, c0, c0, 5	@ read MPIDR
 	and	r0, r0, #0xc0000000	@ multiprocessing extensions and
 	teq	r0, #0x80000000		@ not part of a uniprocessor system?
-	moveq	pc, lr			@ yes, assume SMP
+	bne    __fixup_smp_on_up	@ no, assume UP
+
+	@ Core indicates it is SMP. Check for Aegis SOC where a single
+	@ Cortex-A9 CPU is present but SMP operations fault.
+	mov	r4, #0x41000000
+	orr	r4, r4, #0x0000c000
+	orr	r4, r4, #0x00000090
+	teq	r3, r4			@ Check for ARM Cortex-A9
+	movne	pc, lr			@ Not ARM Cortex-A9,
+
+	@ If a future SoC *does* use 0x0 as the PERIPH_BASE, then the
+	@ below address check will need to be #ifdef'd or equivalent
+	@ for the Aegis platform.
+	mrc	p15, 4, r0, c15, c0	@ get SCU base address
+	teq	r0, #0x0		@ '0' on actual UP A9 hardware
+	beq	__fixup_smp_on_up	@ So its an A9 UP
+	ldr	r0, [r0, #4]		@ read SCU Config
+	and	r0, r0, #0x3		@ number of CPUs
+	teq	r0, #0x0		@ is 1?
+	movne	pc, lr
 
 __fixup_smp_on_up:
 	adr	r0, 1f