From 6220f8d8338a17b0af5dde5d99d890fba7660cfe Mon Sep 17 00:00:00 2001
From: Patrick Rudolph <patrick.rudolph@9elements.com>
Date: Fri, 22 Feb 2019 12:06:41 +0100
Subject: [PATCH] soc/cavium/cn81xx: Enable RNG for DRAM init
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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>
---
 src/soc/cavium/cn81xx/sdram.c | 46 +++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)

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