[PATCH V6 5/8] vfio: platform: call _RST method when using ACPI

Sinan Kaya okaya at codeaurora.org
Sun Jun 12 20:41:04 PDT 2016

On 6/8/2016 6:31 PM, Rafael J. Wysocki wrote:
> On Sun, May 29, 2016 at 12:01 AM, Sinan Kaya <okaya at codeaurora.org> wrote:
>> The device tree code checks for the presence of a reset driver and calls
>> the of_reset function pointer by looking up the reset driver as a module.
>> ACPI defines _RST method to perform device level reset. After the _RST
>> method is executed, the OS can resume using the device. _RST method is
>> expected to stop DMA transfers and IRQs.
>> This patch checks the presence of _RST method and calls the _RST
>> method when reset is requested.

A little bit of misinformation here. The current code is checking the presence
during probe time. If the presence of _RST method is required then probe is
aborted. Otherwise, probe will complete execution.

When reset call is to be executed, presence of _RST method is no longer checked.
Instead, the method is directly called. 

I was talking about the contribution of this patch as both here. I'll clarify
the commit message. 

> You could check if _RST is present at probe time and store the ACPI
> handle of it instead of the HID pointer.
> This way you wouldn't need to repeat that check every time reset is used.

Based on the requirement that the code can be executed without the presence
of _RST method for development purposes, I'm hesitant to use the handle of the
reset method as a gating factor.

Sinan Kaya
Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project

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