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[v6,3/7] hw/char/pl011: Introduce pl011_xmit() as GSource

Message ID 20250208163911.54522-4-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 
Extract pl011_xmit() from pl011_write_txdata(). Use the
FIFO to pass the character to be transmitted.

Implement it using the FEWatchFunc prototype, since we want
to register it as GSource later. While the return value is
not yet used, we return G_SOURCE_REMOVE meaning the GSource
is removed from the main loop (because we only send one char).

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 hw/char/pl011.c      | 36 +++++++++++++++++++++++++++++-------
 hw/char/trace-events |  3 +++
 2 files changed, 32 insertions(+), 7 deletions(-)
diff mbox series

Patch

diff --git a/hw/char/pl011.c b/hw/char/pl011.c
index 807fcdee50b..b9c9e5b5983 100644
--- a/hw/char/pl011.c
+++ b/hw/char/pl011.c
@@ -226,6 +226,32 @@  static void pl011_loopback_tx(PL011State *s, uint32_t value)
     pl011_fifo_rx_put(s, value);
 }
 
+static gboolean pl011_xmit(void *do_not_use, GIOCondition cond, void *opaque)
+{
+    PL011State *s = opaque;
+    int bytes_consumed;
+    uint8_t data;
+    uint32_t count;
+
+    count = fifo8_num_used(&s->xmit_fifo);
+    trace_pl011_fifo_tx_xmit_used(count);
+
+    data = fifo8_pop(&s->xmit_fifo);
+    bytes_consumed = 1;
+
+    /*
+     * XXX this blocks entire thread. Rewrite to use
+     * qemu_chr_fe_write and background I/O callbacks
+     */
+    qemu_chr_fe_write_all(&s->chr, &data, bytes_consumed);
+    trace_pl011_fifo_tx_xmit_consumed(bytes_consumed);
+    s->int_level |= INT_TX;
+
+    pl011_update(s);
+
+    return G_SOURCE_REMOVE;
+}
+
 static void pl011_write_txdata(PL011State *s, uint8_t data)
 {
     if (!(s->cr & CR_UARTEN)) {
@@ -237,14 +263,10 @@  static void pl011_write_txdata(PL011State *s, uint8_t data)
                       "PL011 data written to disabled TX UART\n");
     }
 
-    /*
-     * XXX this blocks entire thread. Rewrite to use
-     * qemu_chr_fe_write and background I/O callbacks
-     */
-    qemu_chr_fe_write_all(&s->chr, &data, 1);
+    trace_pl011_fifo_tx_put(data);
     pl011_loopback_tx(s, data);
-    s->int_level |= INT_TX;
-    pl011_update(s);
+    fifo8_push(&s->xmit_fifo, data);
+    pl011_xmit(NULL, G_IO_OUT, s);
 }
 
 static uint32_t pl011_read_rxdata(PL011State *s)
diff --git a/hw/char/trace-events b/hw/char/trace-events
index b2e3d25ae34..3d07866be5c 100644
--- a/hw/char/trace-events
+++ b/hw/char/trace-events
@@ -65,6 +65,9 @@  pl011_write(uint32_t addr, uint32_t value, const char *regname) "addr 0x%03x val
 pl011_can_receive(uint32_t lcr, int read_count, int r) "LCR 0x%08x read_count %d returning %d"
 pl011_fifo_rx_put(uint32_t c, int read_count) "new char 0x%02x read_count now %d"
 pl011_fifo_rx_full(void) "RX FIFO now full, RXFF set"
+pl011_fifo_tx_put(uint8_t byte) "TX FIFO push char [0x%02x]"
+pl011_fifo_tx_xmit_used(unsigned sent) "TX FIFO used %u chars"
+pl011_fifo_tx_xmit_consumed(unsigned sent) "TX FIFO consumed %u chars"
 pl011_baudrate_change(unsigned int baudrate, uint64_t clock, uint32_t ibrd, uint32_t fbrd) "new baudrate %u (clk: %" PRIu64 "hz, ibrd: %" PRIu32 ", fbrd: %" PRIu32 ")"
 
 # cmsdk-apb-uart.c