Re: [Xen-devel] [PATCH v4] ns16550: Add ACPI support for ARM only

[Julien Grall <julien@xen.org>]

On 21/02/2020 14:02, Jan Beulich wrote:
> On 21.02.2020 03:22, Wei Xu wrote:
>> --- a/xen/drivers/char/ns16550.c
>> +++ b/xen/drivers/char/ns16550.c
>> @@ -1620,6 +1620,85 @@ DT_DEVICE_START(ns16550, "NS16550 UART", DEVICE_SERIAL)
>>   DT_DEVICE_END
>>
>>   #endif /* HAS_DEVICE_TREE */
>> +
>> +#if defined(CONFIG_ACPI) && defined(CONFIG_ARM)
>> +#include <xen/acpi.h>
>> +
>> +static int __init ns16550_acpi_uart_init(const void *data)
>> +{
>> +    struct acpi_table_header *table;
>> +    struct acpi_table_spcr *spcr;
>> +    acpi_status status;
>> +    /*
>> +     * Same as the DT part.
>> +     * Only support one UART on ARM which happen to be ns16550_com[0].
>> +     */
>> +    struct ns16550 *uart = &ns16550_com[0];
>> +
>> +    status = acpi_get_table(ACPI_SIG_SPCR, 0, &table);
>> +    if ( ACPI_FAILURE(status) )
>> +    {
>> +        printk("ns16550: Failed to get SPCR table\n");
>> +        return -EINVAL;
>> +    }
>> +
>> +    spcr = container_of(table, struct acpi_table_spcr, header);
>> +
>> +    /*
>> +     * The serial port address may be 0 for example
>> +     * if the console redirection is disabled.
>> +     */
>> +    if ( unlikely(!spcr->serial_port.address) )
>> +    {
>> +        printk("ns16550: Console redirection is disabled\n");
>> +        return -EINVAL;
>> +    }
>> +
>> +    if ( unlikely(spcr->serial_port.space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY) )
>> +    {
>> +        printk("ns16550: Address space type is not mmio\n");
>> +        return -EINVAL;
>> +    }
> 
> The space_id field qualifies the address one, i.e. whether a value of
> zero can sensibly mean "disabled" depends on the address space. Hence
> logically the address space check should come first.
> 
> This is the last thing I'd like to see changed. I won't give the
> patch my ack though, as I think it should be an Arm maintainer to ack
> it.

Acked-by: Julien Grall <julien@xen.org>

Although, a reviewed-by tag from you would be nice as you did most of 
the review for this patch.

Cheers,

-- 
Julien Grall

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