ARM: 8659/1: l2c: allow CA9 optimizations to be disabled

If a PL310 is added to a system, but the sideband signals are not
connected, some Cortex A9 optimizations cannot be used. In particular,
enabling Full Line of Zeros in the CA9 without sidebands connected will
crash the system since the CA9 will expect the L2C to perform operations,
yet the L2C never gets the commands. Early BRESP also does not work
without sideband signals.

Signed-off-by: Chris Brandt <[e-mail]>
Signed-off-by: Russell King <[e-mail]>

Documentation/devicetree/bindings/arm/l2c2x0.txt

···
 - arm,standby-mode: L2 standby mode enable. Value <0> (forcibly disable),
   <1> (forcibly enable), property absent (OS specific behavior,
   preferably retain firmware settings)
+- arm,early-bresp-disable : Disable the CA9 optimization Early BRESP (PL310)
+- arm,full-line-zero-disable : Disable the CA9 optimization Full line of zero
+  write (PL310)
 
 Example:
 

arch/arm/mm/cache-l2x0.c

···
 
 struct l2x0_regs l2x0_saved_regs;
 
+static bool l2x0_bresp_disable;
+static bool l2x0_flz_disable;
+
 /*
  * Common code for all cache controllers.
  */
···
 	u32 aux = l2x0_saved_regs.aux_ctrl;
 
 	if (rev >= L310_CACHE_ID_RTL_R2P0) {
-		if (cortex_a9) {
+		if (cortex_a9 && !l2x0_bresp_disable) {
 			aux |= L310_AUX_CTRL_EARLY_BRESP;
 			pr_info("L2C-310 enabling early BRESP for Cortex-A9\n");
 		} else if (aux & L310_AUX_CTRL_EARLY_BRESP) {
···
 		}
 	}
 
-	if (cortex_a9) {
+	if (cortex_a9 && !l2x0_flz_disable) {
 		u32 aux_cur = readl_relaxed(base + L2X0_AUX_CTRL);
 		u32 acr = get_auxcr();
 
···
 		*aux_val &= ~L2C_AUX_CTRL_PARITY_ENABLE;
 		*aux_mask &= ~L2C_AUX_CTRL_PARITY_ENABLE;
 	}
+
+	if (of_property_read_bool(np, "arm,early-bresp-disable"))
+		l2x0_bresp_disable = true;
+
+	if (of_property_read_bool(np, "arm,full-line-zero-disable"))
+		l2x0_flz_disable = true;
 
 	prefetch = l2x0_saved_regs.prefetch_ctrl;