diff mbox series

[v6,2/7] hw/char/pl011: Add transmit FIFO to PL011State

Message ID 20250208163911.54522-3-philmd@linaro.org
State New
Headers show
Series hw/char/pl011: Implement TX (async) FIFO to avoid blocking the main loop | expand

Commit Message

Philippe Mathieu-Daudé Feb. 8, 2025, 4:39 p.m. UTC 
In order to make the next commit easier to review,
introduce the transmit FIFO, but do not yet use it.

We only migrate the TX FIFO if it is in use.

When migrating from new to old VM:
- if the fifo is empty, migration will still work because
   of the subsection.
- if the fifo is not empty, the subsection will be ignored,
  with the only consequence being that some characters will
  be dropped.

Since the FIFO is created empty, we don't need a migration
pre_load() handler.

Uninline pl011_reset_tx_fifo().

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 include/hw/char/pl011.h |  2 ++
 hw/char/pl011.c         | 37 +++++++++++++++++++++++++++++++++++--
 2 files changed, 37 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/include/hw/char/pl011.h b/include/hw/char/pl011.h
index 4fcaf3d7d30..e8d95961f66 100644
--- a/include/hw/char/pl011.h
+++ b/include/hw/char/pl011.h
@@ -18,6 +18,7 @@ 
 #include "hw/sysbus.h"
 #include "chardev/char-fe.h"
 #include "qom/object.h"
+#include "qemu/fifo8.h"
 
 #define TYPE_PL011 "pl011"
 OBJECT_DECLARE_SIMPLE_TYPE(PL011State, PL011)
@@ -52,6 +53,7 @@  struct PL011State {
     Clock *clk;
     bool migrate_clk;
     const unsigned char *id;
+    Fifo8 xmit_fifo;
 };
 
 DeviceState *pl011_create(hwaddr addr, qemu_irq irq, Chardev *chr);
diff --git a/hw/char/pl011.c b/hw/char/pl011.c
index 60cea1d9a16..807fcdee50b 100644
--- a/hw/char/pl011.c
+++ b/hw/char/pl011.c
@@ -167,11 +167,13 @@  static inline void pl011_reset_rx_fifo(PL011State *s)
     s->flags |= PL011_FLAG_RXFE;
 }
 
-static inline void pl011_reset_tx_fifo(PL011State *s)
+static void pl011_reset_tx_fifo(PL011State *s)
 {
     /* Reset FIFO flags */
     s->flags &= ~PL011_FLAG_TXFF;
     s->flags |= PL011_FLAG_TXFE;
+
+    fifo8_reset(&s->xmit_fifo);
 }
 
 static void pl011_fifo_rx_put(void *opaque, uint32_t value)
@@ -553,6 +555,24 @@  static const VMStateDescription vmstate_pl011_clock = {
     }
 };
 
+static bool pl011_xmit_fifo_state_needed(void *opaque)
+{
+    PL011State* s = opaque;
+
+    return pl011_is_fifo_enabled(s) && !fifo8_is_empty(&s->xmit_fifo);
+}
+
+static const VMStateDescription vmstate_pl011_xmit_fifo = {
+    .name = "pl011/xmit_fifo",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = pl011_xmit_fifo_state_needed,
+    .fields = (VMStateField[]) {
+        VMSTATE_FIFO8(xmit_fifo, PL011State),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 static int pl011_post_load(void *opaque, int version_id)
 {
     PL011State* s = opaque;
@@ -607,7 +627,11 @@  static const VMStateDescription vmstate_pl011 = {
     .subsections = (const VMStateDescription * const []) {
         &vmstate_pl011_clock,
         NULL
-    }
+    },
+    .subsections = (const VMStateDescription * []) {
+        &vmstate_pl011_xmit_fifo,
+        NULL
+    },
 };
 
 static const Property pl011_properties[] = {
@@ -621,6 +645,7 @@  static void pl011_init(Object *obj)
     PL011State *s = PL011(obj);
     int i;
 
+    fifo8_create(&s->xmit_fifo, PL011_FIFO_DEPTH);
     memory_region_init_io(&s->iomem, OBJECT(s), &pl011_ops, s, "pl011", 0x1000);
     sysbus_init_mmio(sbd, &s->iomem);
     for (i = 0; i < ARRAY_SIZE(s->irq); i++) {
@@ -633,6 +658,13 @@  static void pl011_init(Object *obj)
     s->id = pl011_id_arm;
 }
 
+static void pl011_finalize(Object *obj)
+{
+    PL011State *s = PL011(obj);
+
+    fifo8_destroy(&s->xmit_fifo);
+}
+
 static void pl011_realize(DeviceState *dev, Error **errp)
 {
     PL011State *s = PL011(dev);
@@ -676,6 +708,7 @@  static const TypeInfo pl011_arm_info = {
     .parent        = TYPE_SYS_BUS_DEVICE,
     .instance_size = sizeof(PL011State),
     .instance_init = pl011_init,
+    .instance_finalize = pl011_finalize,
     .class_init    = pl011_class_init,
 };