Date:   Wed, 16 May 2018 13:46:25 +0530
From:   poza@...eaurora.org
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Dongdong Liu <liudongdong3@...wei.com>,
        Keith Busch <keith.busch@...el.com>, Wei Zhang <wzhang@...com>,
        Sinan Kaya <okaya@...eaurora.org>,
        Timur Tabi <timur@...eaurora.org>
Subject: Re: [PATCH v16 8/9] PCI/DPC: Unify and plumb error handling into DPC

On 2018-05-16 05:26, Bjorn Helgaas wrote:
> On Fri, May 11, 2018 at 05:22:08PM +0530, poza@...eaurora.org wrote:
>> On 2018-05-11 16:13, Oza Pawandeep wrote:
>> > DPC driver implements link_reset callback, and calls
>> > pci_do_fatal_recovery().
>> >
>> > Which follows standard path of ERR_FATAL recovery.
>> >
>> > Signed-off-by: Oza Pawandeep <poza@...eaurora.org>
>> >
>> > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
>> > index 5e8857a..6af7595 100644
>> > --- a/drivers/pci/pci.h
>> > +++ b/drivers/pci/pci.h
>> > @@ -354,7 +354,7 @@ static inline resource_size_t
>> > pci_resource_alignment(struct pci_dev *dev,
>> >  void pci_enable_acs(struct pci_dev *dev);
>> >
>> >  /* PCI error reporting and recovery */
>> > -void pcie_do_fatal_recovery(struct pci_dev *dev);
>> > +void pcie_do_fatal_recovery(struct pci_dev *dev, u32 service);
>> >  void pcie_do_nonfatal_recovery(struct pci_dev *dev);
>> >
>> >  bool pcie_wait_for_link(struct pci_dev *pdev, bool active);
>> > diff --git a/drivers/pci/pcie/aer/aerdrv_core.c
>> > b/drivers/pci/pcie/aer/aerdrv_core.c
>> > index fdfc474..36e622d 100644
>> > --- a/drivers/pci/pcie/aer/aerdrv_core.c
>> > +++ b/drivers/pci/pcie/aer/aerdrv_core.c
>> > @@ -254,7 +254,7 @@ static void handle_error_source(struct pcie_device
>> > *aerdev,
>> >  	} else if (info->severity == AER_NONFATAL)
>> >  		pcie_do_nonfatal_recovery(dev);
>> >  	else if (info->severity == AER_FATAL)
>> > -		pcie_do_fatal_recovery(dev);
>> > +		pcie_do_fatal_recovery(dev, PCIE_PORT_SERVICE_AER);
>> >  }
>> >
>> >  #ifdef CONFIG_ACPI_APEI_PCIEAER
>> > @@ -321,7 +321,7 @@ static void aer_recover_work_func(struct work_struct
>> > *work)
>> >  		if (entry.severity == AER_NONFATAL)
>> >  			pcie_do_nonfatal_recovery(pdev);
>> >  		else if (entry.severity == AER_FATAL)
>> > -			pcie_do_fatal_recovery(pdev);
>> > +			pcie_do_fatal_recovery(pdev, PCIE_PORT_SERVICE_AER);
>> >  		pci_dev_put(pdev);
>> >  	}
>> >  }
>> > diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
>> > index 80ec384..5680c13 100644
>> > --- a/drivers/pci/pcie/dpc.c
>> > +++ b/drivers/pci/pcie/dpc.c
>> > @@ -73,29 +73,31 @@ static void dpc_wait_link_inactive(struct dpc_dev
>> > *dpc)
>> >  	pcie_wait_for_link(pdev, false);
>> >  }
>> >
>> > -static void dpc_work(struct work_struct *work)
>> > +static pci_ers_result_t dpc_reset_link(struct pci_dev *pdev)
>> >  {
>> > -	struct dpc_dev *dpc = container_of(work, struct dpc_dev, work);
>> > -	struct pci_dev *dev, *temp, *pdev = dpc->dev->port;
>> > -	struct pci_bus *parent = pdev->subordinate;
>> > -	u16 cap = dpc->cap_pos, ctl;
>> > -
>> > -	pci_lock_rescan_remove();
>> > -	list_for_each_entry_safe_reverse(dev, temp, &parent->devices,
>> > -					 bus_list) {
>> > -		pci_dev_get(dev);
>> > -		pci_dev_set_disconnected(dev, NULL);
>> > -		if (pci_has_subordinate(dev))
>> > -			pci_walk_bus(dev->subordinate,
>> > -				     pci_dev_set_disconnected, NULL);
>> > -		pci_stop_and_remove_bus_device(dev);
>> > -		pci_dev_put(dev);
>> > -	}
>> > -	pci_unlock_rescan_remove();
>> > -
>> > +	struct dpc_dev *dpc;
>> > +	struct pcie_device *pciedev;
>> > +	struct device *devdpc;
>> > +	u16 cap, ctl;
>> > +
>> > +	/*
>> > +	 * DPC disables the Link automatically in hardware, so it has
>> > +	 * already been reset by the time we get here.
>> > +	 */
>> > +
>> > +	devdpc = pcie_port_find_device(pdev, PCIE_PORT_SERVICE_DPC);
>> > +	pciedev = to_pcie_device(devdpc);
>> > +	dpc = get_service_data(pciedev);
>> > +	cap = dpc->cap_pos;
>> > +
>> > +	/*
>> > +	 * Waiting until the link is inactive, then clearing DPC
>> > +	 * trigger status to allow the port to leave DPC.
>> > +	 */
>> >  	dpc_wait_link_inactive(dpc);
>> > +
>> >  	if (dpc->rp_extensions && dpc_wait_rp_inactive(dpc))
>> > -		return;
>> > +		return PCI_ERS_RESULT_DISCONNECT;
>> >  	if (dpc->rp_extensions && dpc->rp_pio_status) {
>> >  		pci_write_config_dword(pdev, cap + PCI_EXP_DPC_RP_PIO_STATUS,
>> >  				       dpc->rp_pio_status);
>> > @@ -108,6 +110,17 @@ static void dpc_work(struct work_struct *work)
>> >  	pci_read_config_word(pdev, cap + PCI_EXP_DPC_CTL, &ctl);
>> >  	pci_write_config_word(pdev, cap + PCI_EXP_DPC_CTL,
>> >  			      ctl | PCI_EXP_DPC_CTL_INT_EN);
>> > +
>> > +	return PCI_ERS_RESULT_RECOVERED;
>> > +}
>> > +
>> > +static void dpc_work(struct work_struct *work)
>> > +{
>> > +	struct dpc_dev *dpc = container_of(work, struct dpc_dev, work);
>> > +	struct pci_dev *pdev = dpc->dev->port;
>> > +
>> > +	/* From DPC point of view error is always FATAL. */
>> > +	pcie_do_fatal_recovery(pdev, PCIE_PORT_SERVICE_DPC);
>> >  }
>> >
>> >  static void dpc_process_rp_pio_error(struct dpc_dev *dpc)
>> > @@ -288,6 +301,7 @@ static struct pcie_port_service_driver dpcdriver = {
>> >  	.service	= PCIE_PORT_SERVICE_DPC,
>> >  	.probe		= dpc_probe,
>> >  	.remove		= dpc_remove,
>> > +	.reset_link	= dpc_reset_link,
>> >  };
>> >
>> >  static int __init dpc_service_init(void)
>> > diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
>> > index 33a16b1..29ff148 100644
>> > --- a/drivers/pci/pcie/err.c
>> > +++ b/drivers/pci/pcie/err.c
>> > @@ -185,7 +185,7 @@ static pci_ers_result_t default_reset_link(struct
>> > pci_dev *dev)
>> >  	return PCI_ERS_RESULT_RECOVERED;
>> >  }
>> >
>> > -static pci_ers_result_t reset_link(struct pci_dev *dev)
>> > +static pci_ers_result_t reset_link(struct pci_dev *dev, u32 service)
>> >  {
>> >  	struct pci_dev *udev;
>> >  	pci_ers_result_t status;
>> > @@ -200,7 +200,7 @@ static pci_ers_result_t reset_link(struct pci_dev
>> > *dev)
>> >  	}
>> >
>> >  	/* Use the aer driver of the component firstly */
>> > -	driver = pcie_port_find_service(udev, PCIE_PORT_SERVICE_AER);
>> > +	driver = pcie_port_find_service(udev, service);
>> >
>> >  	if (driver && driver->reset_link) {
>> >  		status = driver->reset_link(udev);
>> > @@ -287,7 +287,7 @@ static pci_ers_result_t
>> > broadcast_error_message(struct pci_dev *dev,
>> >   * followed by re-enumeration of devices.
>> >   */
>> >
>> > -void pcie_do_fatal_recovery(struct pci_dev *dev)
>> > +void pcie_do_fatal_recovery(struct pci_dev *dev, u32 service)
>> >  {
>> >  	struct pci_dev *udev;
>> >  	struct pci_bus *parent;
>> > @@ -313,7 +313,7 @@ void pcie_do_fatal_recovery(struct pci_dev *dev)
>> >  		pci_dev_put(pdev);
>> >  	}
>> >
>> > -	result = reset_link(udev);
>> > +	result = reset_link(udev, service);
>> >
>> >  	if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
>> >  		/*
>> > diff --git a/include/linux/aer.h b/include/linux/aer.h
>> > index 8f87bbe..0c506fe 100644
>> > --- a/include/linux/aer.h
>> > +++ b/include/linux/aer.h
>> > @@ -14,6 +14,7 @@
>> >  #define AER_NONFATAL			0
>> >  #define AER_FATAL			1
>> >  #define AER_CORRECTABLE			2
>> > +#define DPC_FATAL			4
> 
> I think DPC_FATAL can be 3, since these values are not used as a bit 
> mask.
> 
>> >  struct pci_dev;
>> 
>> 
>> Hi Bjorn,
>> 
>> 
>> I have addressed all the comments, and I hope we are heading towards
>> closure.
>> 
>> I just figure that pcie_do_fatal_recovery  (which is getting executed 
>> for
>> DPC as well)
>> 
>> if (result == PCI_ERS_RESULT_RECOVERED) {
>>                 if (pcie_wait_for_link(udev, true))
>>                         pci_rescan_bus(udev->bus);
>>                 pci_info(dev, "Device recovery successful\n");
>>         }
>> 
>> I have to correct it to
>> 
>> if (service==AER  && result == PCI_ERS_RESULT_RECOVERED) {
>>                 if (pcie_wait_for_link(udev, true))
>>                         pci_rescan_bus(udev->bus);
>>                 pci_info(dev, "Device recovery successful\n");
>>         }
> 
> This patch is mostly a restructuring of DPC and doesn't really change 
> its
> behavior.  DPC didn't previously call pcie_wait_for_link() or
> pci_rescan_bus(), so I agree that adding the "service==AER" test will
> help preserve the existing DPC behavior.
> 
> However, the rescan should happen with DPC *somewhere* and we should
> clarify where that is.  Maybe for now we only need a comment about 
> where
> that happens.  Ideally, we could eventually converge this so the same
> mechanism is used for AER and DPC, so we wouldn't need a test like
> "service=AER".
> 
>> rest of the things look okay to me.
>> If you have any more comments,
>> I can fix them with this one and hopefully v17 will be the final one.


I am sorry I pasted the wrong snippet.
following needs to be fixed in v17.
from:
    if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
                 /*
                  * If the error is reported by a bridge, we think this 
error
                  * is related to the downstream link of the bridge, so 
we
                  * do error recovery on all subordinates of the bridge 
instead
                  * of the bridge and clear the error status of the 
bridge.
                  */
                 pci_walk_bus(dev->subordinate, report_resume, 
&result_data);
                 pci_cleanup_aer_uncorrect_error_status(dev);
         }


to

    if (service==AER  && dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
                 /*
                  * If the error is reported by a bridge, we think this 
error
                  * is related to the downstream link of the bridge, so 
we
                  * do error recovery on all subordinates of the bridge 
instead
                  * of the bridge and clear the error status of the 
bridge.
                  */
                 pci_walk_bus(dev->subordinate, report_resume, 
&result_data);
                 pci_cleanup_aer_uncorrect_error_status(dev);
         }

this is only needed in case of AER.

by the way I can not find pci/oza-v16 branch when I cloned
  git clone 
https://kernel.googlesource.com/pub/scm/linux/kernel/git/helgaas/pci

Regards,
Oza.


>> 
>> 
>> PS: I am going though the code more, and we can have some follow up 
>> patches
>> (probably some cleanup)
>> for e.g. pcie_portdrv_slot_reset()  checks
>> if (dev->error_state == pci_channel_io_frozen) {
>> 		dev->state_saved = true;
>> 		pci_restore_state(dev);
>> 		pcie_portdrv_restore_config(dev);
>> 		pci_enable_pcie_error_reporting(dev);
>> 	}
>> 
>> 
>> but now since the ERR_FATAL path does not call pcie_portdrv_slot_reset 
>> the
>> check is meaning less.
>> 
>> besides driver's shut_down callbacks might want to handle
>> pci_channel_io_frozen, but that something left to be discussed later.
>> So, I am not touching dev->error_state anywhere as of now in ERR_FATAL 
>> case.
>> 
>> Regards,
>> Oza.
>> 
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