> On 21 Jul 2025, at 12:41, Jonathan Cameron <jonathan.came...@huawei.com>
> wrote:
>
> On Fri, 18 Jul 2025 19:20:44 +0300
> Vadim Chichikalyuk <chichikal...@gmail.com> wrote:
>
>> On the ARM virt machine, there is currently no way to programmatically
>> discover the frequency of the UART reference clock solely through the use of
>> UEFI/ACPI (without the DTB). The SPCR table can include this information
>> as of revision 3.
>>
>> Bump the revision to 3 and add the clock frequency of 24 MHz to the table.
>
> Maybe add something on why you aren't just skipping forwards to 4 and filling
> in the rest of the stuff?
Haven’t really considered that – you’re right, might as well upgrade it to
revision 4.
Based on build_dsdt() and acpi_dsdt_add_uart(), the NamespaceString would be
“\_SB.COM0”, right? Although, for some reason, it’s just “.” for RISC-V virt
(indicating
that there isn’t a corresponding device in the ACPI namespace), despite there
being
entries for the UART in the DSDT, just as for ARM?
The relevant lines, for reference (hw/arm/virt-acpi-build.c):
scope = aml_scope("\\_SB");
acpi_dsdt_add_uart(scope, &memmap[VIRT_UART0], (irqmap[VIRT_UART0] +
ARM_SPI_BASE), 0);
static void acpi_dsdt_add_uart(Aml *scope, const MemMapEntry *uart_memmap,
uint32_t uart_irq) {
Aml *dev = aml_device("COM%d", uartidx);
...
}
Thanks for the review,
Vadim
