Re: [Xen-devel] [PATCH 3/3 v3] xen: Fix 16550 UART console for HP Moonshot (Aarch64) platform

[Graeme Gregory <graeme.gregory@xxxxxxxxxx>]

On 27 November 2017 at 10:30, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
> + Graeme
>
> On 27/11/17 10:06, Jan Beulich wrote:
>>>>>
>>>>> On 24.11.17 at 12:39, <bhupinder.thakur@xxxxxxxxxx> wrote:
>>>
>>> --- a/xen/drivers/char/ns16550.c
>>> +++ b/xen/drivers/char/ns16550.c
>>> @@ -1571,6 +1571,30 @@ DT_DEVICE_END
>>>   #endif /* HAS_DEVICE_TREE */
>>>     #if defined(CONFIG_ACPI) && defined(CONFIG_ARM)
>>> +/*
>>> + * APM X-Gene v1 and v2 UART hardware is an 16550 like device but has
>>> its
>>> + * register aligned to 32-bit. In addition, the BIOS also encoded the
>>> + * access width to be 8 bits. This function detects this errata
>>> condition.
>>> + */
>>> +static bool xgene_8250_erratum_present(struct acpi_table_spcr *tb)
>>
>>
>> Is this really to be considered an erratum? From the description it
>> doesn't sound like this couldn't have been a deliberate decision.
>> IOW - does their behavior contradict any spec? (ACPI not providing
>> information in field and access width looks suspicious too - GAS fields
>> exist for both.)
>
>
> I believe the problem here is the firmware table does not describe correctly
> the hardware. I have CCed Graeme which might be able to confirm.
>
Yup, their firmware is wrong, we did tell them many times!

Graeme

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