From 1e5b1899ccea8b69e3393c7ed2040aef8b33a9e8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= <philmd@linaro.org>
Date: Wed, 11 Jan 2023 09:50:15 +0100
Subject: [PATCH] hw/i2c/bitbang_i2c: Trace state changes
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Trace bitbang state machine changes with trace events.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Acked-by: Corey Minyard <cminyard@mvista.com>
Message-id: 20230111085016.44551-5-philmd@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 hw/i2c/bitbang_i2c.c | 33 ++++++++++++++++++++++++++++-----
 hw/i2c/trace-events  |  3 +++
 2 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/hw/i2c/bitbang_i2c.c b/hw/i2c/bitbang_i2c.c
index bf4b781393..efc49b7502 100644
--- a/hw/i2c/bitbang_i2c.c
+++ b/hw/i2c/bitbang_i2c.c
@@ -16,6 +16,7 @@
 #include "hw/sysbus.h"
 #include "qemu/module.h"
 #include "qom/object.h"
+#include "trace.h"
 
 //#define DEBUG_BITBANG_I2C
 
@@ -26,15 +27,41 @@ do { printf("bitbang_i2c: " fmt , ## __VA_ARGS__); } while (0)
 #define DPRINTF(fmt, ...) do {} while(0)
 #endif
 
+/* bitbang_i2c_state enum to name */
+static const char * const sname[] = {
+#define NAME(e) [e] = stringify(e)
+    NAME(STOPPED),
+    [SENDING_BIT7] = "SENDING_BIT7 (START)",
+    NAME(SENDING_BIT6),
+    NAME(SENDING_BIT5),
+    NAME(SENDING_BIT4),
+    NAME(SENDING_BIT3),
+    NAME(SENDING_BIT2),
+    NAME(SENDING_BIT1),
+    NAME(SENDING_BIT0),
+    NAME(WAITING_FOR_ACK),
+    [RECEIVING_BIT7] = "RECEIVING_BIT7 (ACK)",
+    NAME(RECEIVING_BIT6),
+    NAME(RECEIVING_BIT5),
+    NAME(RECEIVING_BIT4),
+    NAME(RECEIVING_BIT3),
+    NAME(RECEIVING_BIT2),
+    NAME(RECEIVING_BIT1),
+    NAME(RECEIVING_BIT0),
+    NAME(SENDING_ACK),
+    NAME(SENT_NACK)
+#undef NAME
+};
+
 static void bitbang_i2c_set_state(bitbang_i2c_interface *i2c,
                                   bitbang_i2c_state state)
 {
+    trace_bitbang_i2c_state(sname[i2c->state], sname[state]);
     i2c->state = state;
 }
 
 static void bitbang_i2c_enter_stop(bitbang_i2c_interface *i2c)
 {
-    DPRINTF("STOP\n");
     if (i2c->current_addr >= 0)
         i2c_end_transfer(i2c->bus);
     i2c->current_addr = -1;
@@ -73,7 +100,6 @@ int bitbang_i2c_set(bitbang_i2c_interface *i2c, int line, int level)
             return bitbang_i2c_nop(i2c);
         }
         if (level == 0) {
-            DPRINTF("START\n");
             /* START condition.  */
             bitbang_i2c_set_state(i2c, SENDING_BIT7);
             i2c->current_addr = -1;
@@ -122,7 +148,6 @@ int bitbang_i2c_set(bitbang_i2c_interface *i2c, int line, int level)
             /* NACK (either addressing a nonexistent device, or the
              * device we were sending to decided to NACK us).
              */
-            DPRINTF("Got NACK\n");
             bitbang_i2c_set_state(i2c, SENT_NACK);
             bitbang_i2c_enter_stop(i2c);
             return bitbang_i2c_ret(i2c, 1);
@@ -147,11 +172,9 @@ int bitbang_i2c_set(bitbang_i2c_interface *i2c, int line, int level)
 
     case SENDING_ACK:
         if (data != 0) {
-            DPRINTF("NACKED\n");
             bitbang_i2c_set_state(i2c, SENT_NACK);
             i2c_nack(i2c->bus);
         } else {
-            DPRINTF("ACKED\n");
             bitbang_i2c_set_state(i2c, RECEIVING_BIT7);
         }
         return bitbang_i2c_ret(i2c, 1);
diff --git a/hw/i2c/trace-events b/hw/i2c/trace-events
index 52dbd53a23..48aee4887c 100644
--- a/hw/i2c/trace-events
+++ b/hw/i2c/trace-events
@@ -1,5 +1,8 @@
 # See docs/devel/tracing.rst for syntax documentation.
 
+# bitbang_i2c.c
+bitbang_i2c_state(const char *old_state, const char *new_state) "state %s -> %s"
+
 # core.c
 
 i2c_event(const char *event, uint8_t address) "%s(addr:0x%02x)"