From ea7db5c21e98d39c95dd520b864c0b69e8f0e65d Mon Sep 17 00:00:00 2001
From: Sebastian Huber <sebastian.huber@embedded-brains.de>
Date: Thu, 20 Jul 2023 19:47:31 +0200
Subject: Add basic DSU support present on GR712RC

Only the time tag counter register is implemented so far.  It may be
used by clock drivers as a free-running counter to measure time.
---
 grlib.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 grlib.h |  3 ++-
 leon3.c |  1 +
 3 files changed, 60 insertions(+), 1 deletion(-)

diff --git a/grlib.c b/grlib.c
index 29785d3..a1ef781 100644
--- a/grlib.c
+++ b/grlib.c
@@ -1784,3 +1784,60 @@ s5test_add (int irq, uint32 addr, uint32 mask)
 const struct grlib_ipcore s5test = {
   NULL, NULL, NULL, s5test_write, s5test_add
 };
+
+
+/* -------------------  Debug Support Unit (DSU)  -----------------------*/
+
+#define DSU_TIME_TAG_COUNTER	0x08
+
+static void
+dsu_init (void)
+{
+}
+
+static void
+dsu_add (int irq, uint32 addr, uint32 mask)
+{
+  grlib_ahbspp_add (GRLIB_PP_ID (VENDOR_GAISLER, GAISLER_DSU, 0, 0),
+		    GRLIB_PP_AHBADDR (addr, mask, 1, 1, 2), 0, 0, 0);
+  if (sis_verbose)
+    printf (" DSU                                0x%08x\n", addr);
+}
+
+static void
+dsu_reset (void)
+{
+}
+
+static int
+dsu_read (uint32 addr, uint32 * data)
+{
+  switch (addr & 0xff)
+    {
+    case DSU_TIME_TAG_COUNTER:		/* 0x08 */
+      /*
+       * On some implementations, a number of upper bits are zero.  For
+       * example, the GR712RC time tag has only 30 bits implemented.  Assume
+       * that the software knows how many bits are present and performs the
+       * necessary masking operations.
+       */
+      *data = sregs[cpu].simtime;
+      break;
+
+    default:
+      *data = 0;
+      break;
+    }
+
+  return 1;
+}
+
+static int
+dsu_write (uint32 addr, uint32 * data, uint32 sz)
+{
+  return 1;
+}
+
+const struct grlib_ipcore dsu = {
+  dsu_init, dsu_reset, dsu_read, dsu_write, dsu_add
+};
diff --git a/grlib.h b/grlib.h
index b182884..a88cb6b 100644
--- a/grlib.h
+++ b/grlib.h
@@ -32,6 +32,7 @@
 /* Devices */
 
 #define GAISLER_LEON3	0x003
+#define GAISLER_DSU	0x004
 #define GAISLER_APBMST	0x006
 #define GAISLER_SRCTRL	0x008
 #define GAISLER_SDCTRL	0x009
@@ -105,4 +106,4 @@ extern void apbuart_restore_stdio (void);
 extern void apbuart_close_port (void);
 extern void apbuart_flush (void);
 extern const struct grlib_ipcore gptimer, irqmp, apbuart, apbmst,
-  greth, l2c, leon3s, srctrl, ns16550, clint, plic, sdctrl, s5test;
+  dsu, greth, l2c, leon3s, srctrl, ns16550, clint, plic, sdctrl, s5test;
diff --git a/leon3.c b/leon3.c
index d833689..0bf6cbe 100644
--- a/leon3.c
+++ b/leon3.c
@@ -65,6 +65,7 @@ init_sim (void)
 
   grlib_ahbs_add (&apbmst, 0, APBSTART, 0xFFF);
   grlib_ahbs_add (&sdctrl, 0, RAM_START, RAM_MASKPP);
+  grlib_ahbs_add (&dsu, 0, 0x90000000, 0xFFF);
 
   grlib_apb_add (&apbuart, 3, APBSTART + 0x100, 0xFFF);
   grlib_apb_add (&irqmp, 0, APBSTART + 0x200, 0xFFF);
-- 
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