Commit 9111971f33 for qemu.org

commit 9111971f3350e00df2fe10112e5796a434915579
Author: julia <midnight@trainwit.ch>
Date:   Thu Jan 15 15:26:29 2026 +0000

    hw/char/cmsdk-apb-uart.c: log guest_errors for r/w to disabled uart

    I don't want to admit how many hours I spent trying to figure out why
    nothing was being printed (as the enable-ing code hadn't yet run,
    even thought it existed).

    Signed-off-by: julia <midnight@trainwit.ch>
    Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
    Message-id: 20251217-cmsdk-uart-disabled-warning2-v1-1-847de48840bc@trainwit.ch
    Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

diff --git a/hw/char/cmsdk-apb-uart.c b/hw/char/cmsdk-apb-uart.c
index bf891081dc..edb80f6181 100644
--- a/hw/char/cmsdk-apb-uart.c
+++ b/hw/char/cmsdk-apb-uart.c
@@ -159,6 +159,10 @@ static uint64_t uart_read(void *opaque, hwaddr offset, unsigned size)
     switch (offset) {
     case A_DATA:
         r = s->rxbuf;
+        if (!(s->ctrl & R_CTRL_RX_EN_MASK)) {
+            qemu_log_mask(LOG_GUEST_ERROR,
+                          "CMSDK APB UART: receive data read with Rx disabled\n");
+        }
         s->state &= ~R_STATE_RXFULL_MASK;
         cmsdk_apb_uart_update(s);
         qemu_chr_fe_accept_input(&s->chr);
@@ -248,6 +252,10 @@ static void uart_write(void *opaque, hwaddr offset, uint64_t value,
     switch (offset) {
     case A_DATA:
         s->txbuf = value;
+        if (!(s->ctrl & R_CTRL_TX_EN_MASK)) {
+            qemu_log_mask(LOG_GUEST_ERROR,
+                          "CMSDK APB UART: transmit data write with Tx disabled\n");
+        }
         if (s->state & R_STATE_TXFULL_MASK) {
             /* Buffer already full -- note the overrun and let the
              * existing pending transmit callback handle the new char.