irqchip/gic-v3: Init SRE before poking sysregs

The GICv3 driver pokes GICv3 system registers in gic_prio_init() before
gic_cpu_sys_reg_init() ensures that GICv3 system registers have been
enabled by writing to ICC_SRE_EL1.SRE.

On arm64 this is benign as has_useable_gicv3_cpuif() runs earlier during
cpufeature detection, and this enables the GICv3 system registers.

On 32-bit arm when booting on an FVP using the boot-wrapper, the accesses
in gic_prio_init() end up being UNDEFINED and crashes the kernel during
boot.

This is a regression introduced by the addition of gic_prio_init().

Fix this by factoring out the SRE initialization into a new function and
calling it early in the three paths where SRE may not have been
initialized:

(1) gic_init_bases(), before the primary CPU pokes GICv3 sysregs in
    gic_prio_init().

(2) gic_starting_cpu(), before secondary CPUs initialize GICv3 sysregs
    in gic_cpu_init().

(3) gic_cpu_pm_notifier(), before CPUs re-initialize GICv3 sysregs in
    gic_cpu_sys_reg_init().

Fixes: d447bf09 ("irqchip/gic-v3: Detect GICD_CTRL.DS and SCR_EL3.FIQ earlier")
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Cc: stable@vger.kernel.org

drivers/irqchip/irq-gic-v3.c

@@ -1154,14 +1154,8 @@ static void gic_update_rdist_properties(void)
 			gic_data.rdists.has_vpend_valid_dirty ? "Valid+Dirty " : "");
 }
 
-static void gic_cpu_sys_reg_init(void)
+static void gic_cpu_sys_reg_enable(void)
 {
-	int i, cpu = smp_processor_id();
-	u64 mpidr = gic_cpu_to_affinity(cpu);
-	u64 need_rss = MPIDR_RS(mpidr);
-	bool group0;
-	u32 pribits;
-
 	/*
 	 * Need to check that the SRE bit has actually been set. If
 	 * not, it means that SRE is disabled at EL2. We're going to
@@ -1172,6 +1166,16 @@ static void gic_cpu_sys_reg_init(void)
 	if (!gic_enable_sre())
 		pr_err("GIC: unable to set SRE (disabled at EL2), panic ahead\n");
 
+}
+
+static void gic_cpu_sys_reg_init(void)
+{
+	int i, cpu = smp_processor_id();
+	u64 mpidr = gic_cpu_to_affinity(cpu);
+	u64 need_rss = MPIDR_RS(mpidr);
+	bool group0;
+	u32 pribits;
+
 	pribits = gic_get_pribits();
 
 	group0 = gic_has_group0();
@@ -1333,6 +1337,7 @@ static int gic_check_rdist(unsigned int cpu)
 
 static int gic_starting_cpu(unsigned int cpu)
 {
+	gic_cpu_sys_reg_enable();
 	gic_cpu_init();
 
 	if (gic_dist_supports_lpis())
@@ -1498,6 +1503,7 @@ static int gic_cpu_pm_notifier(struct notifier_block *self,
 	if (cmd == CPU_PM_EXIT) {
 		if (gic_dist_security_disabled())
 			gic_enable_redist(true);
+		gic_cpu_sys_reg_enable();
 		gic_cpu_sys_reg_init();
 	} else if (cmd == CPU_PM_ENTER && gic_dist_security_disabled()) {
 		gic_write_grpen1(0);
@@ -2070,6 +2076,7 @@ static int __init gic_init_bases(phys_addr_t dist_phys_base,
 
 	gic_update_rdist_properties();
 
+	gic_cpu_sys_reg_enable();
 	gic_prio_init();
 	gic_dist_init();
 	gic_cpu_init();