drivers/marvell: check if TRNG unit is present

Some Marvell SoCs may have crypto engine disabled in the HW.
This patch checks the AP LD0 efuse for crypto engine/TRNG
presence before initializing the driver.

Change-Id: I441e7c69a137106bd36302b028b04c0b31896dbd
Signed-off-by: Konstantin Porotchkin <kostap@marvell.com>
Reviewed-on: https://sj1git1.cavium.com/c/IP/SW/boot/atf/+/47314

Tested-by: sa_ip-sw-jenkins <sa_ip-sw-jenkins@marvell.com>
Reviewed-by: Yi Guo <yi.guo@cavium.com>

drivers/marvell/mochi/cp110_setup.c

@@ -14,6 +14,7 @@
 #include <drivers/marvell/mochi/cp110_setup.h>
 #include <drivers/rambus/trng_ip_76.h>
 
+#include <efuse_def.h>
 #include <plat_marvell.h>
 
 /*
@@ -110,6 +111,8 @@
  * TRNG Configuration
  ******************************************************************************/
 #define MVEBU_TRNG_BASE					(0x760000)
+#define MVEBU_EFUSE_TRNG_ENABLE_EFUSE_WORD		MVEBU_AP_LDX_220_189_EFUSE_OFFS
+#define MVEBU_EFUSE_TRNG_ENABLE_BIT_OFFSET		13	/* LD0[202] */
 
 enum axi_attr {
 	AXI_ADUNIT_ATTR = 0,
@@ -389,6 +392,22 @@ static void cp110_trng_init(uintptr_t base)
 {
 	static bool done;
 	int ret;
+	uint32_t reg_val, efuse;
+
+	/* Set access to LD0 */
+	reg_val = mmio_read_32(MVEBU_AP_EFUSE_SRV_CTRL_REG);
+	reg_val &= ~EFUSE_SRV_CTRL_LD_SELECT_MASK;
+	mmio_write_32(MVEBU_AP_EFUSE_SRV_CTRL_REG, reg_val);
+
+	/* Obtain the AP LD0 bit defining TRNG presence */
+	efuse = mmio_read_32(MVEBU_EFUSE_TRNG_ENABLE_EFUSE_WORD);
+	efuse >>= MVEBU_EFUSE_TRNG_ENABLE_BIT_OFFSET;
+	efuse &= 1;
+
+	if (efuse == 0) {
+		VERBOSE("TRNG is not present, skipping");
+		return;
+	}
 
 	if (!done) {
 		ret = eip76_rng_probe(base + MVEBU_TRNG_BASE);