Subject: Re: [PATCH] - PCI EEH pci_restore_state fix allowing for repeated adapter recovery per state save

From: Benjamin Herrenschmidt <[email-masked]>
Date: Thu, 10 Jun 2010 16:48:09 +1000

On Thu, 2010-06-03 at 17:45 -0700, Brad Peters wrote:
> Patch Overview:
> The pci_restore_state API is shared by both power management code and Extended
> Error Handling (EEH) code on Power.  This patch adds an additional recovery
> function to pci_restore_state API.  The problem being addressed is that Power
> Management semantics only allow the saved state of PCI device to be restored
> once per save.  With this patch, EEH is able to restore the saved state
> each time a PCI error is detected, enabling recovery in the face of repeated errors.

You should at the very least send that to the PCI maintainer (Jesse
Barnes), though I would recommend the linux-pci list and CC lkml.

Cheers,
Ben.

> There was some discussion of renaming the existing and new functions to more
> clearly break out unconditional restore from the default conditional one, but a
> name change seemed a heavy-handed change to force on the 200+ current users.
> 
> Bit more detail:
> PCI device drivers which support EEH/AER save their  pci state once during
> driver initialization and during EEH/AER error recovery, restore the
> original saved state.  What we found was that our pci driver code would
> recover from the first EEH error and fail to recover on subsequent
> EEH errors. This issue results from pci_restore_state() function
> restoring the state during initialization on the first EEH error.
> 
> What this patch does is to provide the pci_force_restore_state() for use
> by PCI drivers which support EEH/AER that require the original saved
> state be restored each time an EEH/AER error is detected.
> 
> 
> Signed-off by: Brad Peters <[email-masked]>
> Signed-off by: Richard A Lary <[email-masked]>
> 
> -- 
> Brad Peters
> IBM
> Linux on System-P Platform Serviceability Team Lead
> [email-masked]
> 
> 
> -----------------
> 
> 
> diff -uNrp -X linux-2.6.34/Documentation/dontdiff
> linux-2.6.34.orig/drivers/pci/pci.c linux-2.6.34/drivers/pci/pci.c
> --- linux-2.6.34.orig/drivers/pci/pci.c	2010-05-16 14:17:36.000000000 -0700
> +++ linux-2.6.34/drivers/pci/pci.c	2010-05-26 17:16:20.000000000 -0700
> @@ -920,19 +920,11 @@ pci_save_state(struct pci_dev *dev)
>  	return 0;
>  }
> 
> -/**
> - * pci_restore_state - Restore the saved state of a PCI device
> - * @dev: - PCI device that we're dealing with
> - */
> -int
> -pci_restore_state(struct pci_dev *dev)
> +static void __pci_restore_state(struct pci_dev *dev)
>  {
>  	int i;
>  	u32 val;
> 
> -	if (!dev->state_saved)
> -		return 0;
> -
>  	/* PCI Express register must be restored first */
>  	pci_restore_pcie_state(dev);
> 
> @@ -953,12 +945,44 @@ pci_restore_state(struct pci_dev *dev)
>  	pci_restore_pcix_state(dev);
>  	pci_restore_msi_state(dev);
>  	pci_restore_iov_state(dev);
> +}
> +
> +
> +/**
> + * pci_restore_state - Restore the saved state of a PCI device
> + *                     only if dev->state_saved is not 0. Used by
> + *                     power management suspend/restore routines.
> + * @dev: - PCI device that we're dealing with
> + */
> +int
> +pci_restore_state(struct pci_dev *dev)
> +{
> +
> +	if (!dev->state_saved)
> +		return 0;
> +
> +	__pci_restore_state(dev);
> 
>  	dev->state_saved = false;
> 
>  	return 0;
>  }
> 
> +/**
> + * pci_force_restore_state - Restore the saved state of a PCI device
> + *                           even if dev->state_saved is 0. Used by
> + *                           EEH and AER PCI error recovery.
> + * @dev: - PCI device that we're dealing with
> + */
> +int
> +pci_force_restore_state(struct pci_dev *dev)
> +{
> +	__pci_restore_state(dev);
> +
> +	return 0;
> +}
> +
> +
> 
>  static int do_pci_enable_device(struct pci_dev *dev, int bars)
>  {
>  	int err;
> @@ -3039,6 +3063,7 @@ EXPORT_SYMBOL(pci_select_bars);
>  EXPORT_SYMBOL(pci_set_power_state);
>  EXPORT_SYMBOL(pci_save_state);
>  EXPORT_SYMBOL(pci_restore_state);
> +EXPORT_SYMBOL(pci_force_restore_state);
>  EXPORT_SYMBOL(pci_pme_capable);
>  EXPORT_SYMBOL(pci_pme_active);
>  EXPORT_SYMBOL(pci_wake_from_d3);
> diff -uNrp -X linux-2.6.34/Documentation/dontdiff
> linux-2.6.34.orig/include/linux/pci.h linux-2.6.34/include/linux/pci.h
> --- linux-2.6.34.orig/include/linux/pci.h	2010-05-16 14:17:36.000000000 -0700
> +++ linux-2.6.34/include/linux/pci.h	2010-05-26 17:16:21.000000000 -0700
> @@ -792,6 +792,7 @@ size_t pci_get_rom_size(struct pci_dev *
>  /* Power management related routines */
>  int pci_save_state(struct pci_dev *dev);
>  int pci_restore_state(struct pci_dev *dev);
> +int pci_force_restore_state(struct pci_dev *dev);
>  int __pci_complete_power_transition(struct pci_dev *dev, pci_power_t state);
>  int pci_set_power_state(struct pci_dev *dev, pci_power_t state);
>  pci_power_t pci_choose_state(struct pci_dev *dev, pm_message_t state);
> @@ -1155,6 +1156,11 @@ static inline int pci_restore_state(stru
>  	return 0;
>  }
> 
> +static inline int pci_force_restore_state(struct pci_dev *dev)
> +{
> +	return 0;
> +}
> +
>  static inline int pci_set_power_state(struct pci_dev *dev, pci_power_t state)
>  {
>  	return 0;
> 
> 
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