sep: add simple SEP TRNG API

Signed-off-by: Sven Peter <sven@svenpeter.dev>

Makefile

@@ -101,6 +101,7 @@ OBJECTS := \
 	ringbuffer.o \
 	rtkit.o \
 	sart.o \
+	sep.o \
 	smp.o \
 	start.o \
 	startup.o \

src/main.c

@@ -20,6 +20,7 @@
 #include "payload.h"
 #include "pcie.h"
 #include "pmgr.h"
+#include "sep.h"
 #include "smp.h"
 #include "string.h"
 #include "uart.h"
@@ -148,6 +149,7 @@ void m1n1_main(void)
     pmgr_init();
     clk_init();
     cpufreq_init();
+    sep_init();
 
     printf("Initialization complete.\n");
 

src/sep.c

@@ -0,0 +1,68 @@
+/* SPDX-License-Identifier: MIT */
+
+#include <string.h>
+
+#include "asc.h"
+#include "sep.h"
+#include "types.h"
+#include "utils.h"
+
+#define SEP_MSG_EP   GENMASK(7, 0)
+#define SEP_MSG_CMD  GENMASK(23, 16)
+#define SEP_MSG_DATA GENMASK(63, 32)
+
+#define SEP_EP_ROM 0xff
+
+#define SEP_MSG_GETRAND   16
+#define SEP_REPLY_GETRAND 116
+
+#define SEP_TIMEOUT 1000
+
+static asc_dev_t *sep_asc = NULL;
+
+int sep_init(void)
+{
+    if (!sep_asc)
+        sep_asc = asc_init("/arm-io/sep");
+    if (!sep_asc)
+        return -1;
+    return 0;
+}
+
+size_t sep_get_random(void *buffer, size_t len)
+{
+    const struct asc_message msg_getrand = {.msg0 = FIELD_PREP(SEP_MSG_EP, SEP_EP_ROM) |
+                                                    FIELD_PREP(SEP_MSG_CMD, SEP_MSG_GETRAND)};
+    int ret;
+    size_t done = 0;
+
+    ret = sep_init();
+    if (ret)
+        return 0;
+
+    while (len) {
+        struct asc_message reply;
+        u32 rng;
+        size_t copy;
+
+        if (!asc_send(sep_asc, &msg_getrand))
+            return done;
+        if (!asc_recv_timeout(sep_asc, &reply, SEP_TIMEOUT))
+            return done;
+        if (FIELD_GET(SEP_MSG_CMD, reply.msg0) != SEP_REPLY_GETRAND) {
+            printf("SEP: unexpected getrand reply: %016lx\n", reply.msg0);
+            return done;
+        }
+
+        rng = FIELD_GET(SEP_MSG_DATA, reply.msg0);
+        copy = sizeof(rng);
+        if (copy > len)
+            copy = len;
+        memcpy(buffer, &rng, copy);
+        done += copy;
+        len -= copy;
+        buffer += copy;
+    }
+
+    return done;
+}

src/sep.h

@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: MIT */
+
+#ifndef SEP_H
+#define SEP_H
+
+#include "asc.h"
+#include "types.h"
+
+int sep_init(void);
+size_t sep_get_random(void *buffer, size_t len);
+
+#endif