Re: [PATCH 03/14] rtc: block registration of rtc-cmos when CMOS RTC Not Present

H. Peter Anvin
2013-12-20T04:20:54Z

On 12/19/2013 07:54 PM, joeyli wrote:
> Hi hpa,
>
> 於 四，2013-12-19 於 06:38 -0800，H. Peter Anvin 提到：
>> Where did you find a platform with "no CMOS" set and a PNP RTC? I find the expect behavior in that case to be quite ambiguous and it is not at all clear to me that what you have here is the right thing.
>
> Actually there doesn't have the box both with "No CMOS" and PNP device.
> I choice to totally block rtc-cmos driver when "No CMOS RTC" because the
> definition in ACPI spec:
>
> CMOS RTC Not Present
>
> If set, indicates that the CMOS RTC is either not implemented, or
> does not exist at the legacy addresses. OSPM uses the Control
> Method Time and Alarm Namespace device instead.
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
> It suggest us using ACPI TAD interface when this flag present. But, I
> agreed your point for this is ambiguous due to ACPI spec didn't clear
> define the relationship between PNP0B0x.
>
> Maybe we can do more detail check in cmos_init when "No CMOS RTC" set:
> + check if have ACPI TAD device, then block rtc-cmos
> + check if no ACPI TAD device, but have PNP0B0x, then we use PNP0b0x.
>

I think the only thing we should use that bit for is to inhibit the
last-resort probing of I/O ports 0x70-0x73... if at all.

-hpa

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