[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [PATCH qemu.git v2 1/1] hw/arm/virt: make second UART available
From: |
Peter Maydell |
Subject: |
Re: [PATCH qemu.git v2 1/1] hw/arm/virt: make second UART available |
Date: |
Fri, 13 Jan 2023 12:49:07 +0000 |
On Thu, 1 Dec 2022 at 14:30, ~axelheider <axelheider@git.sr.ht> wrote:
>
> From: Axel Heider <axel.heider@hensoldt.net>
>
> The first UART always always exists. If the security extensions are
> enabled, the second UART also always exists. Otherwise, it only exists
> if a backend is configured explicitly via '-serial <backend>', where
> 'null' creates a dummy backend. This allows enabling the second UART
> explicitly on demand and does not interfere with any existing setup
> that just expect one (or two if security extensions are enabled)
> UARTs.
>
> Signed-off-by: Axel Heider <axel.heider@hensoldt.net>
Hi; just wanted to say that this is still on my to-review list.
As a preliminary note:
> @@ -2222,11 +2250,12 @@ static void machvirt_init(MachineState *machine)
>
> fdt_add_pmu_nodes(vms);
>
> - create_uart(vms, VIRT_UART, sysmem, serial_hd(0));
> + create_uart(vms, VIRT_UART0, sysmem, serial_hd(0));
> + create_uart(vms, VIRT_UART1, vms->secure ? secure_sysmem : sysmem,
> + serial_hd(1));
Creating the UARTs in this order in the code results in
them appearing in the DTB in reverse order. (I forget why;
I think dtb nodes put on a list in one order and then
put into the dtb proper in the other, or something.)
The result is that if you add an extra '-serial foo'
argument then Linux decides that UART0 is ttyAMA1 and
UART1 is ttyAMA0, which is a bit counter-intuitive.
This can be avoided by something like:
@@ -2289,9 +2289,20 @@ static void machvirt_init(MachineState *machine)
fdt_add_pmu_nodes(vms);
+ /*
+ * These end up in the DTB in reverse order of creation, so
+ * we must create UART0 last to ensure it appears as the
+ * first UART, ttyAMA0, for Linux.
+ * For back-compatibility with older QEMU versions, if UART1 is
+ * the secure UART and thus always created, we create it second.
+ */
+ if (!vms->secure) {
+ create_uart(vms, VIRT_UART1, sysmem, serial_hd(1));
+ }
create_uart(vms, VIRT_UART0, sysmem, serial_hd(0));
- create_uart(vms, VIRT_UART1, vms->secure ? secure_sysmem : sysmem,
- serial_hd(1));
+ if (vms->secure) {
+ create_uart(vms, VIRT_UART1, secure_sysmem, serial_hd(1));
+ }
if (vms->secure) {
create_secure_ram(vms, secure_sysmem, secure_tag_sysmem);
I still need to:
* look at what UEFI does if presented with this DTB
(may involve filing a bug report to see if they will
change the enumeration order if it's still silly)
* check what happens when we boot Linux passing it the
h/w info via ACPI
thanks
-- PMM
[Prev in Thread] |
Current Thread |
[Next in Thread] |
- Re: [PATCH qemu.git v2 1/1] hw/arm/virt: make second UART available,
Peter Maydell <=