soc/cavium/cn81xx: Enable RNG for DRAM init

The Cavium DRAM init might use the RNG for pattern generation.
Initialize it before running DRAM init.

Tested on OpenCellular Elgon.
The RNG generates non identical numbers.

Change-Id: I886f920e9941793fb76b56cc5a24a42e23b082e0
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/31567
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

1 files changed, 46 insertions, 0 deletions

diff --git a/src/soc/cavium/cn81xx/sdram.c b/src/soc/cavium/cn81xx/sdram.c
index 2342b049ef..05546cc9b1 100644
--- a/src/soc/cavium/cn81xx/sdram.c
+++ b/src/soc/cavium/cn81xx/sdram.c
@@ -3,6 +3,7 @@
  *
  * Copyright 2018       Facebook, Inc.
  * Copyright 2003-2017  Cavium Inc.  <support@cavium.com>
+ * Copyright 2019       9elements Agency GmbH
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -28,17 +29,61 @@
 #include <libbdk-hal/bdk-utils.h>
 #include <libbdk-hal/bdk-l2c.h>
 #include <libdram/libdram-config.h>
+#include <soc/ecam.h>
+#include <device/pci_ops.h>
+#include <device/pci.h>
 
 size_t sdram_size_mb(void)
 {
 	return bdk_dram_get_size_mbytes(0);
 }
 
+#define BDK_RNM_CTL_STATUS	0
+#define BDK_RNM_RANDOM		0x100000
+
+#if ENV_ROMSTAGE
+/* Enable RNG for DRAM init */
+static void rnm_init(void)
+{
+	/* Bus numbers are hardcoded in ASIC. No need to program bridges. */
+	pci_devfn_t dev = PCI_DEV(2, 0, 0);
+
+	u64 *bar = (u64 *)ecam0_get_bar_val(dev, 0);
+	if (!bar) {
+		printk(BIOS_ERR, "RNG: Failed to get BAR0\n");
+		return;
+	}
+
+	printk(BIOS_DEBUG, "RNG: BAR0 at %p\n", bar);
+
+	u64 reg = read64(&bar[BDK_RNM_CTL_STATUS]);
+	/*
+	 * Enables the output of the RNG.
+	 * Entropy enable for random number generator.
+	 */
+	reg |= 3;
+	write64(&bar[BDK_RNM_CTL_STATUS], reg);
+
+	/* Read back after enable so we know it is done. */
+	reg = read64(&bar[BDK_RNM_CTL_STATUS]);
+	/*
+	 * Errata (RNM-22528) First consecutive reads to RNM_RANDOM return same
+	 * value. Before using the random entropy, read RNM_RANDOM at least once
+	 * and discard the data
+	 */
+	reg = read64(&bar[BDK_RNM_RANDOM]);
+	printk(BIOS_SPEW, "RNG: RANDOM %llx\n", reg);
+	reg = read64(&bar[BDK_RNM_RANDOM]);
+	printk(BIOS_SPEW, "RNG: RANDOM %llx\n", reg);
+}
+
 /* based on bdk_boot_dram() */
 void sdram_init(void)
 {
 	printk(BIOS_DEBUG, "Initializing DRAM\n");
 
+	rnm_init();
+
 	/**
 	 * FIXME: second arg is actually a desired frequency if set (the
 	 * function usually obtains frequency via the config). That might
@@ -100,3 +145,4 @@ void sdram_init(void)
 
 	printk(BIOS_INFO, "SDRAM initialization finished.\n");
 }
+#endif