[v2] hw/openrisc/openrisc_sim: keep serial@90000000 as default

Commit Message

Stafford Horne Sept. 8, 2024, 6:27 a.m. UTC

From: Ahmad Fatoum <[e-mail]>

We used to only have a single UART on the platform and it was located at
address 0x90000000. When the number of UARTs was increased to 4, the
first UART remained at it's location, but instead of being the first one
to be registered, it became the last.

This caused QEMU to pick 0x90000300 as the default UART, which broke
software that hardcoded the address of 0x90000000 and expected it's
output to be visible when the user configured only a single console.

This caused regressions[1] in the barebox test suite when updating to a
newer QEMU. As there seems to be no good reason to register the UARTs in
inverse order, let's register them by ascending address, so existing
software can remain oblivious to the additional UART ports.

Changing the order of uart registration alone breaks Linux which
was choosing the UART at 0x90000300 as the default for ttyS0.  To fix
Linux we fix two things in the device tree:

 1. Define stdout-path only one time for the first registerd UART
    instead of incorrectly defining for each UART.
 2. Change the UART alias name from 'uart0' to 'serial0' as almost all
    Linux tty drivers look for an alias starting with "serial".

[1]: https://lore.barebox.org/barebox/[e-mail]/T/#m5da26e8a799033301489a938b5d5667b81cef6ad

Fixes: 777784bda468 ("hw/openrisc: support 4 serial ports in or1ksim")
Signed-off-by: Ahmad Fatoum <[e-mail]>
[stafford: Change to serial0 alias and update change message]
Signed-off-by: Stafford Horne <[e-mail]>
---
Since v1:
 - Stafford is sending the patch for Ahmad now.
 - Added 'Fixes'
 - Only define stdout-path one time.
 - Change alias name from 'uartN' to 'serialN'

 hw/openrisc/openrisc_sim.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

Patch

diff --git a/hw/openrisc/openrisc_sim.c b/hw/openrisc/openrisc_sim.c
index bffd6f721f..2a15a3a4f0 100644
--- a/hw/openrisc/openrisc_sim.c
+++ b/hw/openrisc/openrisc_sim.c
@@ -250,7 +250,7 @@  static void openrisc_sim_serial_init(Or1ksimState *state, hwaddr base,
     void *fdt = state->fdt;
     char *nodename;
     qemu_irq serial_irq;
-    char alias[sizeof("uart0")];
+    char alias[sizeof("serial0")];
     int i;
 
     if (num_cpus > 1) {
@@ -265,7 +265,7 @@  static void openrisc_sim_serial_init(Or1ksimState *state, hwaddr base,
         serial_irq = get_cpu_irq(cpus, 0, irq_pin);
     }
     serial_mm_init(get_system_memory(), base, 0, serial_irq, 115200,
-                   serial_hd(OR1KSIM_UART_COUNT - uart_idx - 1),
+                   serial_hd(uart_idx),
                    DEVICE_NATIVE_ENDIAN);
 
     /* Add device tree node for serial. */
@@ -277,10 +277,13 @@  static void openrisc_sim_serial_init(Or1ksimState *state, hwaddr base,
     qemu_fdt_setprop_cell(fdt, nodename, "clock-frequency", OR1KSIM_CLK_MHZ);
     qemu_fdt_setprop(fdt, nodename, "big-endian", NULL, 0);
 
-    /* The /chosen node is created during fdt creation. */
-    qemu_fdt_setprop_string(fdt, "/chosen", "stdout-path", nodename);
-    snprintf(alias, sizeof(alias), "uart%d", uart_idx);
+    if (uart_idx == 0) {
+        /* The /chosen node is created during fdt creation. */
+        qemu_fdt_setprop_string(fdt, "/chosen", "stdout-path", nodename);
+    }
+    snprintf(alias, sizeof(alias), "serial%d", uart_idx);
     qemu_fdt_setprop_string(fdt, "/aliases", alias, nodename);
+
     g_free(nodename);
 }