[1/2] pci: add option to ignore slot capabilities

This adds flags to struct pci_dev that can be set to request ignoring
attention and power indicators. This is in prepration for devices that
advertise these capabilities, but do not support it.

Signed-off-by: Keith Busch <keith.busch@intel.com>
---
 drivers/pci/hotplug/pciehp_hpc.c | 6 ++++++
 include/linux/pci.h              | 2 ++
 2 files changed, 8 insertions(+)

Hi Keith,

On Mon, Aug 08, 2016 at 02:19:01PM -0600, Keith Busch wrote:
> This adds flags to struct pci_dev that can be set to request ignoring
> attention and power indicators. This is in prepration for devices that
> advertise these capabilities, but do not support it.
> 
> Signed-off-by: Keith Busch <keith.busch@intel.com>
> ---
>  drivers/pci/hotplug/pciehp_hpc.c | 6 ++++++
>  include/linux/pci.h              | 2 ++
>  2 files changed, 8 insertions(+)
> 
> diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
> index 08e84d6..3e6646c 100644
> --- a/drivers/pci/hotplug/pciehp_hpc.c
> +++ b/drivers/pci/hotplug/pciehp_hpc.c
> @@ -804,6 +804,12 @@ struct controller *pcie_init(struct pcie_device *dev)
>  	}
>  	ctrl->pcie = dev;
>  	pcie_capability_read_dword(pdev, PCI_EXP_SLTCAP, &slot_cap);
> +
> +	if (pdev->ignore_aip)
> +		slot_cap &= ~PCI_EXP_SLTCAP_AIP;
> +	if (pdev->ignore_pip)
> +		slot_cap &= ~PCI_EXP_SLTCAP_PIP;
> +

I think we should clear these bits after the ctrl_info() below.
If we clear it immediately, the ctrl_info() will report these bits as cleared,
even though they may be set in hardware.

I don't think we want to put a value into the log that differs from what hardware reports.

>  	ctrl->slot_cap = slot_cap;
>  	mutex_init(&ctrl->ctrl_lock);
>  	init_waitqueue_head(&ctrl->queue);
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 9890906..d8bc530 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -308,6 +308,8 @@ struct pci_dev {
>  						   powered on/off by the
>  						   corresponding bridge */
>  	unsigned int	ignore_hotplug:1;	/* Ignore hotplug events */
> +	unsigned int	ignore_aip:1;		/* Ignore attention indicator */
> +	unsigned int	ignore_pip:1;		/* Ignore power indicator */
>  	unsigned int	d3_delay;	/* D3->D0 transition time in ms */
>  	unsigned int	d3cold_delay;	/* D3cold->D0 transition time in ms */
>  
> -- 
> 2.7.2
> 
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On Fri, Aug 12, 2016 at 05:03:58PM -0700, Sean O. Stalley wrote:
> I think we should clear these bits after the ctrl_info() below.
> If we clear it immediately, the ctrl_info() will report these bits as cleared,
> even though they may be set in hardware.
> 
> I don't think we want to put a value into the log that differs from what hardware reports.

Maybe, I didn't think of it that way. I thought if a user saw the
capabilities in the kernel message, she could reasonably expect what
the pciehp driver is going to do, even though the driver masked off
that behavior.

'lspci' would still show the hardware capabilities if that's okay for
a user. Had I my way, the hardware wouldn't advertise this capability
at all.
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