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

[Wei Xu <xuwei5@hisilicon.com>]

Hi Jan,

On 2020/2/21 23:07, Jan Beulich wrote:
> On 21.02.2020 15:57, Julien Grall wrote:
>> 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.
> 
> Well, to clarify - this is one of the very few (afaict) cases where our
> R-b implying A-b (when people are entitled to ack the respective code)
> gets in the way. If this wasn't the case, I'd have given the former,
> making it clear (also later from just looking at the resulting commit)
> that the (only) ack came from an Arm person.

I will check the address space in the v5 and add your R-b.
Thanks!

Best Regards,
Wei

> 
> Jan
> 
> .
> 


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