Date:   Mon, 27 Jul 2020 18:14:40 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Sean V Kelley <sean.v.kelley@...el.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 7/9] PCI/AER: Add RCEC AER handling

On Mon, 27 Jul 2020 08:19:39 -0700
Sean V Kelley <sean.v.kelley@...el.com> wrote:

> On 27 Jul 2020, at 5:22, Jonathan Cameron wrote:
> 
> > On Fri, 24 Jul 2020 10:22:21 -0700
> > Sean V Kelley <sean.v.kelley@...el.com> wrote:
> >  
> >> The Root Complex Event Collectors(RCEC) appear as peers to Root Ports
> >> and also have the AER capability. So add RCEC support to the current 
> >> AER
> >> service driver and attach the AER service driver to the RCEC device.
> >>
> >> Co-developed-by: Qiuxu Zhuo <qiuxu.zhuo@...el.com>
> >> Signed-off-by: Sean V Kelley <sean.v.kelley@...el.com>
> >> Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@...el.com>  
> >
> > A few questions and comments for this patch.
> >
> > See inline.
> >
> > Jonathan
> >
> >  
> >> ---
> >>  drivers/pci/pcie/aer.c | 34 +++++++++++++++++++++++++++-------
> >>  1 file changed, 27 insertions(+), 7 deletions(-)
> >>
> >> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> >> index f1bf06be449e..7cc430c74c46 100644
> >> --- a/drivers/pci/pcie/aer.c
> >> +++ b/drivers/pci/pcie/aer.c
> >> @@ -303,7 +303,7 @@ int pci_aer_raw_clear_status(struct pci_dev *dev)
> >>  		return -EIO;
> >>
> >>  	port_type = pci_pcie_type(dev);
> >> -	if (port_type == PCI_EXP_TYPE_ROOT_PORT) {
> >> +	if (port_type == PCI_EXP_TYPE_ROOT_PORT || port_type == 
> >> PCI_EXP_TYPE_RC_EC) {
> >>  		pci_read_config_dword(dev, aer + PCI_ERR_ROOT_STATUS, &status);
> >>  		pci_write_config_dword(dev, aer + PCI_ERR_ROOT_STATUS, status);
> >>  	}
> >> @@ -389,6 +389,12 @@ void pci_aer_init(struct pci_dev *dev)
> >>  	pci_add_ext_cap_save_buffer(dev, PCI_EXT_CAP_ID_ERR, sizeof(u32) * 
> >> n);
> >>
> >>  	pci_aer_clear_status(dev);
> >> +
> >> +	if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_EC) {
> >> +		if (!pci_find_ext_capability(dev, PCI_EXT_CAP_ID_RCEC))
> >> +			return;
> >> +		pci_info(dev, "AER: RCEC CAP FOUND and cap_has_rtctl = %d\n", n);  
> >
> > It feels like failing to find an RC_EC extended cap in a RCEC deserved
> > a nice strong error message.  Perhaps this isn't the right place to do 
> > it
> > though.  For that matter, why are we checking for it here?  
> 
> Sorry, I’ve left an in-development output in the code.  Will replace 
> with a check with more meaningful output elsewhere.
> 
> >  
> >> +	}
> >>  }
> >>
> >>  void pci_aer_exit(struct pci_dev *dev)
> >> @@ -577,7 +583,8 @@ static umode_t aer_stats_attrs_are_visible(struct 
> >> kobject *kobj,
> >>  	if ((a == &dev_attr_aer_rootport_total_err_cor.attr ||
> >>  	     a == &dev_attr_aer_rootport_total_err_fatal.attr ||
> >>  	     a == &dev_attr_aer_rootport_total_err_nonfatal.attr) &&  
> >
> > It is a bit ugly to have these called rootport_total_err etc for the 
> > rcec.
> > Perhaps we should just add additional attributes to reflect we are 
> > looking at
> > an RCEC?  
> 
> I was trying to avoid any renaming to reduce churn as I did with my 
> first patch for ACPI / CLX_OSC support.
> Will take a look.
> 
> >  
> >> -	    pci_pcie_type(pdev) != PCI_EXP_TYPE_ROOT_PORT)
> >> +	    ((pci_pcie_type(pdev) != PCI_EXP_TYPE_ROOT_PORT) &&
> >> +	    (pci_pcie_type(pdev) != PCI_EXP_TYPE_RC_EC)))
> >>  		return 0;
> >>
> >>  	return a->mode;
> >> @@ -894,7 +901,10 @@ static bool find_source_device(struct pci_dev 
> >> *parent,
> >>  	if (result)
> >>  		return true;
> >>
> >> -	pci_walk_bus(parent->subordinate, find_device_iter, e_info);
> >> +	if (pci_pcie_type(parent) == PCI_EXP_TYPE_RC_EC)
> >> +		pcie_walk_rcec(parent, find_device_iter, e_info);
> >> +	else
> >> +		pci_walk_bus(parent->subordinate, find_device_iter, e_info);
> >>
> >>  	if (!e_info->error_dev_num) {
> >>  		pci_info(parent, "can't find device of ID%04x\n", e_info->id);
> >> @@ -1030,6 +1040,7 @@ int aer_get_device_error_info(struct pci_dev 
> >> *dev, struct aer_err_info *info)
> >>  		if (!(info->status & ~info->mask))
> >>  			return 0;
> >>  	} else if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT ||
> >> +		   pci_pcie_type(dev) == PCI_EXP_TYPE_RC_EC ||
> >>  	           pci_pcie_type(dev) == PCI_EXP_TYPE_DOWNSTREAM ||
> >>  		   info->severity == AER_NONFATAL) {
> >>
> >> @@ -1182,6 +1193,8 @@ static int set_device_error_reporting(struct 
> >> pci_dev *dev, void *data)
> >>  	int type = pci_pcie_type(dev);
> >>
> >>  	if ((type == PCI_EXP_TYPE_ROOT_PORT) ||
> >> +	    (type == PCI_EXP_TYPE_RC_EC) ||
> >> +	    (type == PCI_EXP_TYPE_RC_END) ||  
> >
> > Why add RC_END here?  
> 
> I’m not clear on your question.  Errors can come from RCEC or RCiEPs.  
> We still need to enable reporting by the RCiEPs.

I was curious to see that we need it in this code path for an RCiEP but
not for a normal EP.  From a quick glance it looks like that is often
done in the drivers for the EPs themselves rather than here.

> 
> >  
> >>  	    (type == PCI_EXP_TYPE_UPSTREAM) ||
> >>  	    (type == PCI_EXP_TYPE_DOWNSTREAM)) {
> >>  		if (enable)
> >> @@ -1206,9 +1219,11 @@ static void 
> >> set_downstream_devices_error_reporting(struct pci_dev *dev,
> >>  {
> >>  	set_device_error_reporting(dev, &enable);
> >>
> >> -	if (!dev->subordinate)
> >> -		return;
> >> -	pci_walk_bus(dev->subordinate, set_device_error_reporting, 
> >> &enable);
> >> +	if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_EC)
> >> +		pcie_walk_rcec(dev, set_device_error_reporting, &enable);
> >> +	else if (dev->subordinate)
> >> +		pci_walk_bus(dev->subordinate, set_device_error_reporting, 
> >> &enable);
> >> +
> >>  }
> >>
> >>  /**
> >> @@ -1306,6 +1321,11 @@ static int aer_probe(struct pcie_device *dev)
> >>  	struct device *device = &dev->device;
> >>  	struct pci_dev *port = dev->port;
> >>
> >> +	/* Limit to Root Ports or Root Complex Event Collectors */
> >> +	if ((pci_pcie_type(port) != PCI_EXP_TYPE_RC_EC) &&
> >> +	    (pci_pcie_type(port) != PCI_EXP_TYPE_ROOT_PORT))
> >> +		return -ENODEV;
> >> +
> >>  	rpc = devm_kzalloc(device, sizeof(struct aer_rpc), GFP_KERNEL);
> >>  	if (!rpc)
> >>  		return -ENOMEM;
> >> @@ -1362,7 +1382,7 @@ static pci_ers_result_t aer_root_reset(struct 
> >> pci_dev *dev)
> >>
> >>  static struct pcie_port_service_driver aerdriver = {
> >>  	.name		= "aer",
> >> -	.port_type	= PCI_EXP_TYPE_ROOT_PORT,
> >> +	.port_type	= PCIE_ANY_PORT,  
> >
> > Why this particular change?  Seems that is a lot wider than simply
> > adding RCEC.  Obviously we'll then drop out in the aer_probe but it
> > is still rather inelegant.  
> 
> In order to extend the service drivers to non-root-port devices (i.e., 
> RCEC), the simple path appeared to only require setting the type to 
> ANY_PORT and catching the needed types arriving in the probe.  Would you 
> prefer extending to a type2?  I’m not sure how one is more elegant 
> than another but open to that approach.  However, this seems to require 
> less code perhaps and seems consistent with most ‘drop-out’ 
> conditional patterns in the kernel.  The same applies to pme.

I'd miss understood this bit.  It's fine as you have it here.

Jonathan

> 
> Thanks,
> 
> Sean
> 
> 
> >  
> >>  	.service	= PCIE_PORT_SERVICE_AER,
> >>
> >>  	.probe		= aer_probe,  

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