[U-Boot] [PATCH v1 7/7] x86: acpi: Don't touch hardware on HW reduced platforms

[Bin Meng]

Hi Andy,

On Sun, Jul 23, 2017 at 12:43 AM, Andy Shevchenko
<andy.shevchenko at gmail.com> wrote:
> On Sat, Jul 22, 2017 at 4:45 PM, Bin Meng <bmeng.cn at gmail.com> wrote:
>> Hi Andy,
>>
>> On Sat, Jul 22, 2017 at 3:32 AM, Andy Shevchenko
>> <andriy.shevchenko at linux.intel.com> wrote:
>>> If ACPI HW reduced bit in FADT is set we should ignore any ACPI hardware
>>> communications.
>>>
>>> Signed-off-by: Andy Shevchenko <andriy.shevchenko at linux.intel.com>
>>> ---
>>>  arch/x86/lib/acpi_table.c | 4 ++++
>>>  1 file changed, 4 insertions(+)
>>>
>>> diff --git a/arch/x86/lib/acpi_table.c b/arch/x86/lib/acpi_table.c
>>> index da6014fb41..3eb101105b 100644
>>> --- a/arch/x86/lib/acpi_table.c
>>> +++ b/arch/x86/lib/acpi_table.c
>>> @@ -463,6 +463,10 @@ ulong write_acpi_tables(ulong start)
>>>
>>>         debug("ACPI: done\n");
>>>
>>> +       /* Don't touch ACPI hardware on HW reduced platforms */
>>> +       if (fadt->flags & ACPI_FADT_HW_REDUCED_ACPI)
>>> +               return current;
>>> +
>>
>> Reviewed-by: Bin Meng <bmeng.cn at gmail.com>
>
> Thanks!
>
>>
>> I assume this is needed on Intel Edison.
>
> Actually it has very little with Edison, though I had stumbled over
> the bug on that platform.
>
> ARM64 support, if any will come, or I even can suggest to try ASUS
> T100 transformer (Baytrail based HW reduced).
>

Just out of curiosity, if the ASUS T100 transformer is BayTrail based,
why is that HW reduced? My understanding is that BayTrail has these
ACPI registers.

>> If that's the case, will you
>> support S3 resume on Edison? And if yes, I believe we will need update
>> acpi_resume() to add the same check there?
>
> It might affect any of HW reduced one, needs to be checked.
>
> I fixed only one issue I found, I didn't look at every places where
> U-Boot goes to ACPI HW,
>

Regards,
Bin