Date:	Fri, 12 Jun 2009 21:51:07 +0000
From:	Andrew Patterson <andrew.patterson@...com>
To:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	Jesse Barnes <jbarnes@...tuousgeek.org>
Subject: Re: [PATCH V4: 2/3] pci: Provide aer support when the error source
 id is bad

On Fri, 2009-06-12 at 11:08 +0800, Zhang, Yanmin wrote:
> When the bus id part of error source id is equal to 0 or nosourceid=1,
> kernel probes the AER status registers of all devices under the root port
> to find the initial error reporter.
> 
> Signed-off-by: Zhang Yanmin <yanmin.zhang@...ux.intel.com>
> 
> ---
> 
> --- linux-2.6_next_pciwalk/drivers/pci/pcie/aer/aerdrv_core.c	2009-06-12 05:31:53.000000000 +0800
> +++ linux-2.6_next_aernoid/drivers/pci/pcie/aer/aerdrv_core.c	2009-06-12 05:39:24.000000000 +0800
> @@ -26,7 +26,9 @@
>  #include "aerdrv.h"
>  
>  static int forceload;
> +static int nosourceid;
>  module_param(forceload, bool, 0);
> +module_param(nosourceid, bool, 0);
>  
>  int pci_enable_pcie_error_reporting(struct pci_dev *dev)
>  {
> @@ -143,34 +145,82 @@ static void set_downstream_devices_error
>  	pci_walk_bus(dev->subordinate, set_device_error_reporting, &enable);
>  }
>  
> -static int find_device_iter(struct device *device, void *data)
> +static int compare_device_id(struct pci_dev *dev, struct aer_err_info *e_info)
>  {
> -	struct pci_dev *dev;
> -	u16 id = *(unsigned long *)data;
> -	u8 secondary, subordinate, d_bus = id >> 8;
> -
> -	if (device->bus == &pci_bus_type) {
> -		dev = to_pci_dev(device);
> -		if (id == ((dev->bus->number << 8) | dev->devfn)) {
> -			/*
> -			 * Device ID match
> -			 */
> -			*(unsigned long*)data = (unsigned long)device;
> -			return 1;
> -		}
> -
> +	if (e_info->id == ((dev->bus->number << 8) | dev->devfn)) {
>  		/*
> -		 * If device is P2P, check if it is an upstream?
> +		 * Device ID match
>  		 */
> -		if (dev->hdr_type & PCI_HEADER_TYPE_BRIDGE) {
> -			pci_read_config_byte(dev, PCI_SECONDARY_BUS,
> -				&secondary);
> -			pci_read_config_byte(dev, PCI_SUBORDINATE_BUS,
> -				&subordinate);
> -			if (d_bus >= secondary && d_bus <= subordinate) {
> -				*(unsigned long*)data = (unsigned long)device;
> -				return 1;
> -			}
> +		e_info->dev = dev;
> +		return 1;
> +	}
> +
> +	return 0;
> +}
> +
> +#define	PCI_BUS(x)	(((x) >> 8) & 0xff)
> +
> +static int find_device_iter(struct pci_dev *dev, void *data)
> +{
> +	int pos;
> +	u32 status;
> +	u32 mask;
> +	u16 reg16;
> +	struct aer_err_info *e_info = (struct aer_err_info *)data;
> +
> +	/*
> +	 * When bus id is equal to 0, it might be a bad id
> +	 * reported by root port.
> +	 */
> +	if (!nosourceid && (PCI_BUS(e_info->id) != 0))
> +		return compare_device_id(dev, e_info);
> +
> +	/*
> +	 * Next is to check when bus id is equal to 0 or
> +	 * nosourceid==y. Some ports might lose the bus
> +	 * id of error source id. We check AER status
> +	 * registers to find the initial reporter.
> +	 */
> +	if (atomic_read(&dev->enable_cnt) == 0)
> +		return 0;
> +	pos = pci_find_capability(dev, PCI_CAP_ID_EXP);
> +	if (!pos)
> +		return 0;
> +	/* Check if AER is enabled */
> +	pci_read_config_word(dev, pos+PCI_EXP_DEVCTL, &reg16);
> +	if (!(reg16 & (
> +		PCI_EXP_DEVCTL_CERE |
> +		PCI_EXP_DEVCTL_NFERE |
> +		PCI_EXP_DEVCTL_FERE |
> +		PCI_EXP_DEVCTL_URRE)))
> +		return 0;
> +	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ERR);
> +	if (!pos)
> +		return 0;
> +
> +	status = 0;
> +	mask = 0;
> +	if (e_info->severity == AER_CORRECTABLE) {
> +		pci_read_config_dword(dev,
> +				pos + PCI_ERR_COR_STATUS,
> +				&status);
> +		pci_read_config_dword(dev,
> +				pos + PCI_ERR_COR_MASK,
> +				&mask);
> +		if (status & ERR_CORRECTABLE_ERROR_MASK & ~mask) {
> +			e_info->dev = dev;
> +			return 1;
> +		}
> +	} else {
> +		pci_read_config_dword(dev,
> +				pos + PCI_ERR_UNCOR_STATUS,
> +				&status);
> +		pci_read_config_dword(dev,
> +				pos + PCI_ERR_UNCOR_MASK,
> +				&mask);
> +		if (status & ERR_UNCORRECTABLE_ERROR_MASK & ~mask) {
> +			e_info->dev = dev;
> +			return 1;
>  		}
>  	}
>  
> @@ -180,33 +230,23 @@ static int find_device_iter(struct devic
>  /**
>   * find_source_device - search through device hierarchy for source device
>   * @parent: pointer to Root Port pci_dev data structure
> - * @id: device ID of agent who sends an error message to this Root Port
> + * @err_info: including detailed error information such like id
>   *
>   * Invoked when error is detected at the Root Port.
>   */
> -static struct device* find_source_device(struct pci_dev *parent, u16 id)
> +static void find_source_device(struct pci_dev *parent,
> +		struct aer_err_info *e_info)
>  {
>  	struct pci_dev *dev = parent;
> -	struct device *device;
> -	unsigned long device_addr;
> -	int status;
> +	int result;
>  
>  	/* Is Root Port an agent that sends error message? */
> -	if (id == ((dev->bus->number << 8) | dev->devfn))
> -		return &dev->dev;
> -
> -	do {
> -		device_addr = id;
> - 		if ((status = device_for_each_child(&dev->dev,
> -			&device_addr, find_device_iter))) {
> -			device = (struct device*)device_addr;
> -			dev = to_pci_dev(device);
> -			if (id == ((dev->bus->number << 8) | dev->devfn))
> -				return device;
> -		}
> - 	}while (status);
> +	result = find_device_iter(dev, e_info);
> +	if (result)
> +		return;
>  
> -	return NULL;
> +	pci_walk_bus(parent->subordinate, find_device_iter, e_info);

Minor nit. This return is redundant.

> +	return;
>  }
>  

Minor. The e_info goes to pointer changes probably belong in a separate
patch.

>  static int report_error_detected(struct pci_dev *dev, void *data)
> @@ -501,12 +541,12 @@ static pci_ers_result_t do_recovery(stru
>   */
>  static void handle_error_source(struct pcie_device * aerdev,
>  	struct pci_dev *dev,
> -	struct aer_err_info info)
> +	struct aer_err_info *info)
>  {
>  	pci_ers_result_t status = 0;
>  	int pos;
>  
> -	if (info.severity == AER_CORRECTABLE) {
> +	if (info->severity == AER_CORRECTABLE) {
>  		/*
>  		 * Correctable error does not need software intevention.
>  		 * No need to go through error recovery process.
> @@ -514,9 +554,9 @@ static void handle_error_source(struct p
>  		pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ERR);
>  		if (pos)
>  			pci_write_config_dword(dev, pos + PCI_ERR_COR_STATUS,
> -					info.status);
> +					info->status);
>  	} else {
> -		status = do_recovery(aerdev, dev, info.severity);
> +		status = do_recovery(aerdev, dev, info->severity);
>  		if (status == PCI_ERS_RESULT_RECOVERED) {
>  			dev_printk(KERN_DEBUG, &dev->dev, "AER driver "
>  				   "successfully recovered\n");
> @@ -673,10 +713,13 @@ static int get_device_error_info(struct 
>  static void aer_isr_one_error(struct pcie_device *p_device,
>  		struct aer_err_source *e_src)
>  {
> -	struct device *s_device;
> -	struct aer_err_info e_info = {0, 0, 0,};
> +	struct aer_err_info *e_info;
>  	int i;
> -	u16 id;
> +
> +	/* struct aer_err_info might be big, so we allocate it with slab */
> +	e_info = kmalloc(sizeof(struct aer_err_info), GFP_KERNEL);
> +	if (e_info == NULL)
> +		return;
>  
Should we get some sort of warning here? We might be concealing PCIe
errors when out of memory.

>  	/*
>  	 * There is a possibility that both correctable error and
> @@ -688,31 +731,37 @@ static void aer_isr_one_error(struct pci
>  		if (!(e_src->status & i))
>  			continue;
>  
> +		memset(e_info, 0, sizeof(struct aer_err_info));
> +
>  		/* Init comprehensive error information */
>  		if (i & PCI_ERR_ROOT_COR_RCV) {
> -			id = ERR_COR_ID(e_src->id);
> -			e_info.severity = AER_CORRECTABLE;
> +			e_info->id = ERR_COR_ID(e_src->id);
> +			e_info->severity = AER_CORRECTABLE;
>  		} else {
> -			id = ERR_UNCOR_ID(e_src->id);
> -			e_info.severity = ((e_src->status >> 6) & 1);
> +			e_info->id = ERR_UNCOR_ID(e_src->id);
> +			e_info->severity = ((e_src->status >> 6) & 1);
>  		}
>  		if (e_src->status &
>  			(PCI_ERR_ROOT_MULTI_COR_RCV |
>  			 PCI_ERR_ROOT_MULTI_UNCOR_RCV))
> -			e_info.flags |= AER_MULTI_ERROR_VALID_FLAG;
> -		if (!(s_device = find_source_device(p_device->port, id))) {
> +			e_info->flags |= AER_MULTI_ERROR_VALID_FLAG;
> +
> +		find_source_device(p_device->port, e_info);
> +		if (e_info->dev == NULL) {
>  			printk(KERN_DEBUG "%s->can't find device of ID%04x\n",
> -				__func__, id);
> +				__func__, e_info->id);
>  			continue;
>  		}
> -		if (get_device_error_info(to_pci_dev(s_device), &e_info) ==
> +		if (get_device_error_info(e_info->dev, e_info) ==
>  				AER_SUCCESS) {
> -			aer_print_error(to_pci_dev(s_device), &e_info);
> +			aer_print_error(e_info->dev, e_info);
>  			handle_error_source(p_device,
> -				to_pci_dev(s_device),
> +				e_info->dev,
>  				e_info);
>  		}
>  	}
> +
> +	kfree(e_info);
>  }
>  
>  /**
> --- linux-2.6_next_pciwalk/drivers/pci/pcie/aer/aerdrv.h	2009-06-12 05:27:46.000000000 +0800
> +++ linux-2.6_next_aernoid/drivers/pci/pcie/aer/aerdrv.h	2009-06-12 05:39:24.000000000 +0800
> @@ -58,6 +58,8 @@ struct header_log_regs {
>  };
>  
>  struct aer_err_info {
> +	struct pci_dev *dev;
> +	u16 id;
>  	int severity;			/* 0:NONFATAL | 1:FATAL | 2:COR */
>  	int flags;
>  	unsigned int status;		/* COR/UNCOR Error Status */
> --- linux-2.6_next_pciwalk/Documentation/PCI/pcieaer-howto.txt	2009-06-12 05:27:40.000000000 +0800
> +++ linux-2.6_next_aernoid/Documentation/PCI/pcieaer-howto.txt	2009-06-12 05:39:24.000000000 +0800
> @@ -60,6 +60,8 @@ forceload, a parameter of type bool, cou
>  be initiated although firmwares have no _OSC support. To enable the
>  walkaround, pls. add aerdriver.forceload=y to kernel boot parameter line
>  when booting kernel. Note that forceload=n by default.


We need a new paragraph here.
> +nosourceid, another parameter of type bool, is used when hardware (mostly
> +chipset) has errata that root ports couldn't get error reporting source id.
>  

Perhaps ".. can be used when broken hardware (mostly chipsets) has root
ports that cannot obtain the reporting source ID."

>  2.3 AER error output
>  When a PCI-E AER error is captured, an error message will be outputed to
> 
> 
> --
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> 
-- 
Andrew Patterson
Hewlett-Packard

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