linux-kernel - Re: [PATCH 1/2] PCI: Allow PCI_DEV_FLAGS_NO_BUS

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Date:   Tue, 16 May 2017 22:14:31 +0200
From:   Auger Eric <eric.auger@...hat.com>
To:     David Daney <david.daney@...ium.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org
Cc:     Jon Masters <jcm@...hat.com>,
        Robert Richter <robert.richter@...ium.com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/2] PCI: Allow PCI_DEV_FLAGS_NO_BUS_RESET to be used on
 bus device.

Hi,

On 16/05/2017 02:17, David Daney wrote:
> When checking to see if a PCI bus can safely be reset, we check to see
> if any of the children have their PCI_DEV_FLAGS_NO_BUS_RESET flag set.
> As these devices are know not to behave well after a bus reset.
nit: s/know/known
> 
> Some PCIe root port bridges also do not behave well after a bus reset,
> sometimes causing the devices behind the bridge to become unusable.
> 
> Add a check for the PCI_DEV_FLAGS_NO_BUS_RESET flag being set in the
> bridge device to allow these bridges to be flagged, and prevent their
> buses from being reset.
> 
> A follow on patch will add a quirk for this type of bridge.
> 
> Signed-off-by: David Daney <david.daney@...ium.com>

Thanks

Eric
> ---
>  drivers/pci/pci.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index b01bd5b..b64e4d1 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -4318,6 +4318,10 @@ static bool pci_bus_resetable(struct pci_bus *bus)
>  {
>  	struct pci_dev *dev;
>  
> +
> +	if (bus->self && (bus->self->dev_flags & PCI_DEV_FLAGS_NO_BUS_RESET))
> +		return false;
> +
>  	list_for_each_entry(dev, &bus->devices, bus_list) {
>  		if (dev->dev_flags & PCI_DEV_FLAGS_NO_BUS_RESET ||
>  		    (dev->subordinate && !pci_bus_resetable(dev->subordinate)))
>