[PATCH v2 5/5] PCI/powerpc/eeh: Add pcibios hooks for preparing to rescan

[Sam Bobroff]

Hi Sergey,

On Thu, Sep 06, 2018 at 02:57:52PM +0300, Sergey Miroshnichenko wrote:
> Reading an empty slot returns all ones, which triggers a false
> EEH error event on PowerNV.
> 
> New callbacks pcibios_rescan_prepare/done are introduced to
> pause/resume the EEH during rescan.

If I understand it correctly, this temporarily disables EEH for config space
accesses on the whole PHB while the rescan runs. Is it possible that a
real EEH event could be missed if it occurred during the rescan?

Even if it's not possible, I think it would be good to mention that in a
comment.

> Signed-off-by: Sergey Miroshnichenko <s.miroshnichenko at yadro.com>
> ---
>  arch/powerpc/include/asm/eeh.h               |  2 ++
>  arch/powerpc/kernel/eeh.c                    | 12 +++++++++++
>  arch/powerpc/platforms/powernv/eeh-powernv.c | 22 ++++++++++++++++++++
>  drivers/pci/probe.c                          | 14 +++++++++++++
>  include/linux/pci.h                          |  2 ++
>  5 files changed, 52 insertions(+)
> 
> diff --git a/arch/powerpc/include/asm/eeh.h b/arch/powerpc/include/asm/eeh.h
> index 219637ea69a1..926c3e31df99 100644
> --- a/arch/powerpc/include/asm/eeh.h
> +++ b/arch/powerpc/include/asm/eeh.h
> @@ -219,6 +219,8 @@ struct eeh_ops {
>  	int (*next_error)(struct eeh_pe **pe);
>  	int (*restore_config)(struct pci_dn *pdn);
>  	int (*notify_resume)(struct pci_dn *pdn);
> +	int (*pause)(struct pci_bus *bus);
> +	int (*resume)(struct pci_bus *bus);

I think these names are a bit too generic, what about naming them
pause_bus()/resume_bus() or even prepare_rescan()/rescan_done()?

>  };
>  
>  extern int eeh_subsystem_flags;
> diff --git a/arch/powerpc/kernel/eeh.c b/arch/powerpc/kernel/eeh.c
> index 6ebba3e48b01..9fb5012f389d 100644
> --- a/arch/powerpc/kernel/eeh.c
> +++ b/arch/powerpc/kernel/eeh.c
> @@ -1831,3 +1831,15 @@ static int __init eeh_init_proc(void)
>  	return 0;
>  }
>  __initcall(eeh_init_proc);
> +
> +void pcibios_rescan_prepare(struct pci_bus *bus)
> +{
> +	if (eeh_ops && eeh_ops->pause)
> +		eeh_ops->pause(bus);
> +}
> +
> +void pcibios_rescan_done(struct pci_bus *bus)
> +{
> +	if (eeh_ops && eeh_ops->resume)
> +		eeh_ops->resume(bus);
> +}
> diff --git a/arch/powerpc/platforms/powernv/eeh-powernv.c b/arch/powerpc/platforms/powernv/eeh-powernv.c
> index 3c1beae29f2d..9724a58afcd2 100644
> --- a/arch/powerpc/platforms/powernv/eeh-powernv.c
> +++ b/arch/powerpc/platforms/powernv/eeh-powernv.c
> @@ -59,6 +59,26 @@ void pnv_pcibios_bus_add_device(struct pci_dev *pdev)
>  	eeh_sysfs_add_device(pdev);
>  }
>  
> +static int pnv_eeh_pause(struct pci_bus *bus)
> +{
> +	struct pci_controller *hose = pci_bus_to_host(bus);
> +	struct pnv_phb *phb = hose->private_data;
> +
> +	phb->flags &= ~PNV_PHB_FLAG_EEH;
> +	disable_irq(eeh_event_irq);
> +	return 0;
> +}
> +
> +static int pnv_eeh_resume(struct pci_bus *bus)
> +{
> +	struct pci_controller *hose = pci_bus_to_host(bus);
> +	struct pnv_phb *phb = hose->private_data;
> +
> +	enable_irq(eeh_event_irq);
> +	phb->flags |= PNV_PHB_FLAG_EEH;
> +	return 0;
> +}
> +
>  static int pnv_eeh_init(void)
>  {
>  	struct pci_controller *hose;
> @@ -1710,6 +1730,8 @@ static struct eeh_ops pnv_eeh_ops = {
>  	.write_config           = pnv_eeh_write_config,
>  	.next_error		= pnv_eeh_next_error,
>  	.restore_config		= pnv_eeh_restore_config,
> +	.pause			= pnv_eeh_pause,
> +	.resume			= pnv_eeh_resume,
>  	.notify_resume		= NULL
>  };
>  
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index ac876e32de4b..4a9045364809 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2801,6 +2801,14 @@ void __weak pcibios_remove_bus(struct pci_bus *bus)
>  {
>  }
>  
> +void __weak pcibios_rescan_prepare(struct pci_bus *bus)
> +{
> +}
> +
> +void __weak pcibios_rescan_done(struct pci_bus *bus)
> +{
> +}
> +
>  struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
>  		struct pci_ops *ops, void *sysdata, struct list_head *resources)
>  {
> @@ -3055,9 +3063,15 @@ unsigned int pci_rescan_bus_bridge_resize(struct pci_dev *bridge)
>  unsigned int pci_rescan_bus(struct pci_bus *bus)
>  {
>  	unsigned int max;
> +	struct pci_bus *root = bus;
> +
> +	while (!pci_is_root_bus(root))
> +		root = root->parent;
>  
> +	pcibios_rescan_prepare(root);
>  	max = pci_scan_child_bus(bus);
>  	pci_assign_unassigned_bus_resources(bus);
> +	pcibios_rescan_done(root);
>  	pci_bus_add_devices(bus);
>  
>  	return max;
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 340029b2fb38..42930731c5a7 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1929,6 +1929,8 @@ void pcibios_penalize_isa_irq(int irq, int active);
>  int pcibios_alloc_irq(struct pci_dev *dev);
>  void pcibios_free_irq(struct pci_dev *dev);
>  resource_size_t pcibios_default_alignment(void);
> +void pcibios_rescan_prepare(struct pci_bus *bus);
> +void pcibios_rescan_done(struct pci_bus *bus);
>  
>  #ifdef CONFIG_HIBERNATE_CALLBACKS
>  extern struct dev_pm_ops pcibios_pm_ops;
> -- 
> 2.17.1
> 
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