linux-kernel - Re: [PATCH 1/2] PCI: save and restore device state during bus reset

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Message-ID: <f01a23c1-3540-02b7-25e6-fc0537195111@codeaurora.org>
Date:   Tue, 13 Sep 2016 19:31:18 -0400
From:   Sinan Kaya <okaya@...eaurora.org>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     linux-pci@...r.kernel.org, timur@...eaurora.org,
        cov@...eaurora.org, alex.williamson@...hat.com,
        vikrams@...eaurora.org, linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] PCI: save and restore device state during bus reset

On 9/13/2016 7:20 PM, Sinan Kaya wrote:
> On 9/13/2016 5:53 PM, Bjorn Helgaas wrote:
>>> +	pci_bus_restore(dev->bus);
>> This path eventually writes the Bridge Control register:
>>
>>   pci_reset_bridge_secondary_bus
>>     pcibios_reset_secondary_bus
>>       pci_reset_secondary_bus
>>         pci_write_config_word(dev, PCI_BRIDGE_CONTROL, ctrl)
>>
>> But I think it'd be easy to call this on a non-bridge device, and I
>> don't think there's anything in the path that checks whether this is
>> actually a bridge.  I wonder if we should check that somewhere, or
>> maybe even change the interface so it takes a struct pci_bus instead
>> of a pci_dev.
>>
> 
> I'll change it to pci_bus.
> 
>>>> +}
> 
> 

Changing the API seems to become a bigger mess. pcibios_reset_secondary_bus has
weaker friends in different architectures.

I can move the check in pci_parent_bus_reset 

         if (pci_is_root_bus(dev->bus) || dev->subordinate ||
             !dev->bus->self || dev->dev_flags & PCI_DEV_FLAGS_NO_BUS_RESET)
                 return -ENOTTY;

inside pci_reset_bridge_secondary_bus instead.

-- 
Sinan Kaya
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.