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Date:   Tue, 15 May 2018 18:56:33 -0500
From:   Bjorn Helgaas <helgaas@kernel.org>
To:     poza@codeaurora.org
Cc:     Bjorn Helgaas <bhelgaas@google.com>,
        Philippe Ombredanne <pombredanne@nexb.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Kate Stewart <kstewart@linuxfoundation.org>,
        linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
        Dongdong Liu <liudongdong3@huawei.com>,
        Keith Busch <keith.busch@intel.com>, Wei Zhang <wzhang@fb.com>,
        Sinan Kaya <okaya@codeaurora.org>,
        Timur Tabi <timur@codeaurora.org>
Subject: Re: [PATCH v16 8/9] PCI/DPC: Unify and plumb error handling into DPC
Message-ID: <20180515235632.GB11156@bhelgaas-glaptop.roam.corp.google.com>
References: <1526035408-31328-1-git-send-email-poza@codeaurora.org>
 <1526035408-31328-9-git-send-email-poza@codeaurora.org>
 <a497fae20a326bdf67395c907a5b6b0d@codeaurora.org>
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On Fri, May 11, 2018 at 05:22:08PM +0530, poza@codeaurora.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@codeaurora.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.
> 
> 
> 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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