target/hppa: Add "diag 0x101" for console output support

For debugging purposes at the early stage of the bootup process,
the SeaBIOS-hppa firmware sometimes needs to output characters to the
serial console. Note that the serial console is the default output
method for parisc machines.

At this stage PCI busses and other devices haven't been initialized
yet. So, SeaBIOS-hppa will not be able to find the correct I/O ports
for the serial ports yet.

Instead, add an emulation for the "diag 0x101" opcode to assist here.
Without any other dependencies, SeaBIOS-hppa can then load the character
to be printed in register %r26 and issue the diag assembly instruction.

The qemu diag_console_output() helper function will then print
that character to the first serial port.

Signed-off-by: Helge Deller <deller@gmx.de>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

diff --git a/target/hppa/helper.h b/target/hppa/helper.h
index 20698f68ed0cb47534920ad5a47a9a2c9cb8b90c..1bdbcd8f98dd4fad44c26c71afcfe0d4fc4b8b7b 100644 (file)
--- a/target/hppa/helper.h
+++ b/target/hppa/helper.h
@@ -103,4 +103,5 @@ DEF_HELPER_FLAGS_1(ptlbe, TCG_CALL_NO_RWG, void, env)
 DEF_HELPER_FLAGS_2(lpa, TCG_CALL_NO_WG, tl, env, tl)
 DEF_HELPER_FLAGS_1(change_prot_id, TCG_CALL_NO_RWG, void, env)
 DEF_HELPER_1(diag_btlb, void, env)
+DEF_HELPER_1(diag_console_output, void, env)
 #endif

diff --git a/target/hppa/sys_helper.c b/target/hppa/sys_helper.c
index a59245eed3672c2d25fffa085f428f7d0a030a4b..4a31748342ff4dfb61bc5ddb9af3b316bc39793b 100644 (file)
--- a/target/hppa/sys_helper.c
+++ b/target/hppa/sys_helper.c
@@ -23,6 +23,8 @@
 #include "exec/helper-proto.h"
 #include "qemu/timer.h"
 #include "sysemu/runstate.h"
+#include "sysemu/sysemu.h"
+#include "chardev/char-fe.h"
 
 void HELPER(write_interval_timer)(CPUHPPAState *env, target_ulong val)
 {
@@ -109,3 +111,37 @@ void HELPER(rfi_r)(CPUHPPAState *env)
     helper_getshadowregs(env);
     helper_rfi(env);
 }
+
+#ifndef CONFIG_USER_ONLY
+/*
+ * diag_console_output() is a helper function used during the initial bootup
+ * process of the SeaBIOS-hppa firmware.  During the bootup phase, addresses of
+ * serial ports on e.g. PCI busses are unknown and most other devices haven't
+ * been initialized and configured yet.  With help of a simple "diag" assembler
+ * instruction and an ASCII character code in register %r26 firmware can easily
+ * print debug output without any dependencies to the first serial port and use
+ * that as serial console.
+ */
+void HELPER(diag_console_output)(CPUHPPAState *env)
+{
+    CharBackend *serial_backend;
+    Chardev *serial_port;
+    unsigned char c;
+
+    /* find first serial port */
+    serial_port = serial_hd(0);
+    if (!serial_port) {
+        return;
+    }
+
+    /* get serial_backend for the serial port */
+    serial_backend = serial_port->be;
+    if (!serial_backend ||
+        !qemu_chr_fe_backend_connected(serial_backend)) {
+        return;
+    }
+
+    c = (unsigned char)env->gr[26];
+    qemu_chr_fe_write(serial_backend, &c, sizeof(c));
+}
+#endif

diff --git a/target/hppa/translate.c b/target/hppa/translate.c
index 08d09d50d766b0f5d14968dd2b18b165526764e7..53ec57ee8667b1025418a19d241fd5099c4a7817 100644 (file)
--- a/target/hppa/translate.c
+++ b/target/hppa/translate.c
@@ -4411,6 +4411,12 @@ static bool trans_diag(DisasContext *ctx, arg_diag *a)
         gen_helper_diag_btlb(tcg_env);
         return nullify_end(ctx);
     }
+    if (a->i == 0x101) {
+        /* print char in %r26 to first serial console, used by SeaBIOS-hppa */
+        nullify_over(ctx);
+        gen_helper_diag_console_output(tcg_env);
+        return nullify_end(ctx);
+    }
 #endif
     qemu_log_mask(LOG_UNIMP, "DIAG opcode 0x%04x ignored\n", a->i);
     return true;