linux-kernel - Re: [RFC PATCH 2/9] PCI: Extend Root Port Driver to support RCEC

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Date:   Mon, 27 Jul 2020 08:05:16 -0700
From:   "Sean V Kelley" <sean.v.kelley@...el.com>
To:     "Jonathan Cameron" <Jonathan.Cameron@...wei.com>
Cc:     bhelgaas@...gle.com, rjw@...ysocki.net, tony.luck@...el.com,
        "Raj, Ashok" <ashok.raj@...el.com>,
        sathyanarayanan.kuppuswamy@...ux.intel.com,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Qiuxu Zhuo" <qiuxu.zhuo@...el.com>
Subject: Re: [RFC PATCH 2/9] PCI: Extend Root Port Driver to support RCEC

On 27 Jul 2020, at 5:30, Jonathan Cameron wrote:

> On Fri, 24 Jul 2020 10:22:16 -0700
> Sean V Kelley <sean.v.kelley@...el.com> wrote:
>
>> From: Qiuxu Zhuo <qiuxu.zhuo@...el.com>
>>
>> If a Root Complex Integrated Endpoint (RCiEP) is implemented, errors 
>> may
>> optionally be sent to a corresponding Root Complex Event Collector 
>> (RCEC).
>> Each RCiEP must be associated with no more than one RCEC. Interface 
>> errors
>> are reported to the OS by RCECs.
>>
>> For an RCEC (technically not a Bridge), error messages "received" 
>> from
>> associated RCiEPs must be enabled for "transmission" in order to 
>> cause a
>> System Error via the Root Control register or (when the Advanced 
>> Error
>> Reporting Capability is present) reporting via the Root Error Command
>> register and logging in the Root Error Status register and Error 
>> Source
>> Identification register.
>>
>> Given the commonality with Root Ports and the need to also support 
>> AER
>> and PME services for RCECs, extend the Root Port driver to support 
>> RCEC
>> devices through the addition of the RCEC Class ID to the driver
>> structure.
>>
> Hi.
>
> I'm surprised it ended up this simple :) Seems we are a bit lucky that
> the existing code is rather flexible on what is there and what isn't
> and that there is never any reason to directly touch the various
> type1 specific registers (given as I read the spec, an RCEC uses a
> type0 config space header unlike the ports).

Which is part of the reason why I chose to refer to it as an RFC, 
because it seemed simpler and I was unsure if we were missing anything, 
and it turns out we were. Unfortunately, to avoid churn, I’ve left 
quite a bit of comments/naming intact with “root”/“port” terms.

>
> Given you mention PME, it's probably worth noting (I think) you aren't
> actually enabling the service yet as there is a check in that path on 
> whether we
> have a root port or not.
> https://elixir.bootlin.com/linux/v5.8-rc4/source/drivers/pci/pcie/portdrv_core.c#L241

Good catch, testing has been only done at this point with AER injection.
Will correct.

Thanks,

Sean

>
> Thanks,
>
> Jonathan
>
>
>> Co-developed-by: Sean V Kelley <sean.v.kelley@...el.com>
>> Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@...el.com>
>> Signed-off-by: Sean V Kelley <sean.v.kelley@...el.com>
>> ---
>>  drivers/pci/pcie/portdrv_pci.c | 5 ++++-
>>  1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/pci/pcie/portdrv_pci.c 
>> b/drivers/pci/pcie/portdrv_pci.c
>> index 3acf151ae015..d5b109499b10 100644
>> --- a/drivers/pci/pcie/portdrv_pci.c
>> +++ b/drivers/pci/pcie/portdrv_pci.c
>> @@ -106,7 +106,8 @@ static int pcie_portdrv_probe(struct pci_dev 
>> *dev,
>>  	if (!pci_is_pcie(dev) ||
>>  	    ((pci_pcie_type(dev) != PCI_EXP_TYPE_ROOT_PORT) &&
>>  	     (pci_pcie_type(dev) != PCI_EXP_TYPE_UPSTREAM) &&
>> -	     (pci_pcie_type(dev) != PCI_EXP_TYPE_DOWNSTREAM)))
>> +	     (pci_pcie_type(dev) != PCI_EXP_TYPE_DOWNSTREAM) &&
>> +	     (pci_pcie_type(dev) != PCI_EXP_TYPE_RC_EC)))
>>  		return -ENODEV;
>>
>>  	status = pcie_port_device_register(dev);
>> @@ -195,6 +196,8 @@ static const struct pci_device_id port_pci_ids[] 
>> = {
>>  	{ PCI_DEVICE_CLASS(((PCI_CLASS_BRIDGE_PCI << 8) | 0x00), ~0) },
>>  	/* subtractive decode PCI-to-PCI bridge, class type is 060401h */
>>  	{ PCI_DEVICE_CLASS(((PCI_CLASS_BRIDGE_PCI << 8) | 0x01), ~0) },
>> +	/* handle any Root Complex Event Collector */
>> +	{ PCI_DEVICE_CLASS(((PCI_CLASS_SYSTEM_RCEC << 8) | 0x00), ~0) },
>>  	{ },
>>  };
>>