msm: Add support for early random numbers

Currently, the software random number generator is not initialized
until relatively late in the boot process. Software that relies on
random numbers early will not be reliable. Entropy sources are
available early but not early enough for some use cases which means
that moving the software random number generation earlier is not an
option. Instead we initialize the random pool with values from a
HW RNG accessed through a call to the secure environment.

Change-Id: Id756a8740df7ec938984c3e7de22681e0270bb5b
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
[ohaugan@codeaurora.org: Removed unsupported scm api]
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>

drivers/soc/qcom/Kconfig

@@ -349,6 +349,14 @@ config QCOM_COMMAND_DB
 	  Command DB queries shared memory by key string for shared system
 	  resources
 
+config QCOM_EARLY_RANDOM
+        bool "Initialize random pool very early"
+        help
+          The standard random pool may not initialize until late in the boot
+          process which means that any calls to get random numbers before then
+          may not be truly random. Select this option to make an early call
+          to get some random data to put in the pool. If unsure, say N.
+
 config QTI_RPMH_API
 	bool "QTI RPMH (h/w accelerators) Communication API"
 	select MAILBOX

drivers/soc/qcom/Makefile

@@ -19,6 +19,7 @@ obj-$(CONFIG_QCOM_SMSM)	+= smsm.o
 obj-$(CONFIG_QCOM_WCNSS_CTRL) += wcnss_ctrl.o
 CFLAGS_scm.o :=$(call as-instr,.arch_extension sec,-DREQUIRES_SEC=1)
 obj-$(CONFIG_QCOM_SCM)  +=      scm.o
+obj-$(CONFIG_QCOM_EARLY_RANDOM)	+= early_random.o
 obj-$(CONFIG_SOC_BUS) += socinfo.o
 obj-$(CONFIG_MSM_BOOT_STATS) += boot_stats.o
 obj-$(CONFIG_MSM_CORE_HANG_DETECT) += core_hang_detect.o

drivers/soc/qcom/early_random.c

@@ -0,0 +1,56 @@
+/* Copyright (c) 2013-2014, 2016-2017, The Linux Foundation. All rights
+ * reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/random.h>
+#include <linux/io.h>
+
+#include <soc/qcom/scm.h>
+
+#include <asm/cacheflush.h>
+
+#define TZ_SVC_CRYPTO	10
+#define PRNG_CMD_ID	0x01
+
+struct tz_prng_data {
+	uint8_t		*out_buf;
+	uint32_t	out_buf_sz;
+} __packed;
+
+DEFINE_SCM_BUFFER(common_scm_buf);
+#define RANDOM_BUFFER_SIZE	PAGE_SIZE
+char random_buffer[RANDOM_BUFFER_SIZE] __aligned(PAGE_SIZE);
+
+void __init init_random_pool(void)
+{
+	struct tz_prng_data data;
+	int ret;
+	struct scm_desc desc;
+
+	data.out_buf = (uint8_t *) virt_to_phys(random_buffer);
+	desc.args[0] = (unsigned long) data.out_buf;
+	desc.args[1] = data.out_buf_sz = SZ_512;
+	desc.arginfo = SCM_ARGS(2, SCM_RW, SCM_VAL);
+
+	dmac_flush_range(random_buffer, random_buffer + RANDOM_BUFFER_SIZE);
+
+	ret = scm_call2(SCM_SIP_FNID(TZ_SVC_CRYPTO, PRNG_CMD_ID), &desc);
+
+	if (!ret) {
+		dmac_inv_range(random_buffer, random_buffer +
+						RANDOM_BUFFER_SIZE);
+		add_device_randomness(random_buffer, SZ_512);
+	}
+}
+