[PATCH V7 5/7] ACPI: Delay the enumeration on the devices whose dependency has not met

Arnd Bergmann arnd at arndb.de
Thu Mar 16 03:13:01 PDT 2017

On Thu, Mar 16, 2017 at 3:21 AM, zhichang.yuan
<yuanzhichang at hisilicon.com> wrote:
> Hi, Rafael,
> Thanks for your review!
> On 2017/3/14 5:24, Rafael J. Wysocki wrote:
>> On Monday, March 13, 2017 10:42:41 AM zhichang.yuan wrote:
>>> In commit 40e7fcb1929(ACPI: Add _DEP support to fix battery issue on Asus
>>> T100TA), the '_DEP' was supported to solve the dependency of Asus battery. But
>>> this patch is specific to Asus battery device.
>>> In the real world, there are other devices which need the dependency to play the
>>> role on the enumeration order. For example, all the Hip06 LPC
>>> periperals(IPMI-BT, uart, etc) must be scanned after the LPC host driver
>>> finished the probing. So, it makes sense to add a checking whether the ACPI
>>> device meet all the dependencies during its enumeration slot, if not, the
>>> enumeration will be delayed till all dependency master finish their work.
>>> This patch adds the dependency checking in ACPI enumeration, also the
>>> corresponding handling to retrigger the Hip06 LPC peripherals' scanning.
>> AFAICS, _DEP is generally abused in the wild and cannot be made generic.  Sorry.
> From the ACPI specification, _DEP is for operation region accesses.
> You are right...
> How about we add a ACPI handler for our LPC bus?? Just like amba.
> In this way, we also can solve the issue about LPC enumeration order.

As far as I can tell, PCI and LPC have exactly the same requirement here,
so whatever you end up doing for one should be used for the other as well.


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