Re: [PATCH v16 8/9] PCI/DPC: Unify and plumb error handling into DPC

poza@xxxxxxxxxxxxxx · Wed, 16 May 2018 13:46:25 +0530

On 2018-05-16 05:26, Bjorn Helgaas wrote:
On Fri, May 11, 2018 at 05:22:08PM +0530, poza@xxxxxxxxxxxxxx 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@xxxxxxxxxxxxxx>
>
> 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.