[Question] eDPC and DPC settings in BIOS or Kernel?

[Question] eDPC and DPC settings in BIOS or Kernel?

[Gabriele Paoloni]

Hi Keith and all

We are currently working on extending the current DPC driver
In Linux with eDPC features.

While working on it we are wondering on whether "RP PIO Mask Register"
and "RP PIO Severity Register" should be set in BIOS or Kernel.

If we look at the current DPC driver we see that DPC is enabled in
kernel and "DPC Trigger Enable" is set to 10b where instead the PCIe
specs says that "DPC is disabled by default".

Consistently for "RP PIO Severity Register" and "RP PIO Mask Register"
we see that their bits defaults to 0b and 1b respectively (i.e. by
defaults all RP PIO events are masked and treated as Advisory Non-Fatal).

So we have some questions:
1) Why the current "DPC Trigger Enable" is enabled in Kernel rather than
   BIOS? (enabling it in BIOS seems more scalable to fit different systems'
   scenarios)

2) Do you have any advice on where to enable and unmask RP PIO events?

Many thanks
Gab

RE: [Question] eDPC and DPC settings in BIOS or Kernel?

[Gabriele Paoloni]

Hello

Any feedback on this?

Thanks
Gab

> -----Original Message-----
> From: linux-pci-owner@vger.kernel.org [mailto:linux-pci-
> owner@vger.kernel.org] On Behalf Of Gabriele Paoloni
> Sent: 18 May 2017 11:02
> To: Keith Busch
> Cc: linux-pci@vger.kernel.org; Linuxarm; liudongdong (C)
> Subject: [Question] eDPC and DPC settings in BIOS or Kernel?
> 
> Hi Keith and all
> 
> We are currently working on extending the current DPC driver
> In Linux with eDPC features.
> 
> While working on it we are wondering on whether "RP PIO Mask Register"
> and "RP PIO Severity Register" should be set in BIOS or Kernel.
> 
> If we look at the current DPC driver we see that DPC is enabled in
> kernel and "DPC Trigger Enable" is set to 10b where instead the PCIe
> specs says that "DPC is disabled by default".
> 
> Consistently for "RP PIO Severity Register" and "RP PIO Mask Register"
> we see that their bits defaults to 0b and 1b respectively (i.e. by
> defaults all RP PIO events are masked and treated as Advisory Non-
> Fatal).
> 
> So we have some questions:
> 1) Why the current "DPC Trigger Enable" is enabled in Kernel rather
> than
>    BIOS? (enabling it in BIOS seems more scalable to fit different
> systems'
>    scenarios)
> 
> 2) Do you have any advice on where to enable and unmask RP PIO events?
> 
> Many thanks
> Gab