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Message-ID: <20120322032819.GA4689@shangw>
Date: Thu, 22 Mar 2012 11:28:19 +0800
From: Gavin Shan <shangw@...ux.vnet.ibm.com>
To: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc: sfr@...b.auug.org.au, grant.likely@...retlab.ca,
linux-kernel@...r.kernel.org, linux-next@...r.kernel.org,
paulus@...ba.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] EEH: remove eeh device from OF node
>> Originally, the PCI sensitive OF node is tracing the eeh device
>> through struct device_node::edev. However, it was regarded as
>> bad idea.
>>
>> The patch removes struct device_node::edev. In addition, the
>> global list of eeh devices is introduced, and do retrival of
>> eeh device according to the given OF node through the global
>> list.
>
>So I'm not too happy with that. The main problem I see is that
>the code -constantly- calls of_node_to_eeh_dev.
>
Yes, it's somewhat expensive.
>IE. On any MMIO that happens to return all 1's, we'll call
>eeh_check_failure() for example, which does that. In fact for a hot path
>it's pretty horrid, it will:
>
> - Do an address cache lookup to get the pci_dev
> - Get the device-node frokm the pci_dev
> - Lookup your list to get the eeh_dev
>
>Shouldn't we instead change the address cache to contain eeh_dev
>instead ? And if you prefer keeping pci_dev, then it shouldn't be hard
>to stick a pointer to the eeh_dev in there via either struct archdata or
>maybe platform_data.
>
>The EEH code still, even after your rework, constantly pass "dn"'s as
>argument to functions just to convert it back to a struct eeh_dev rather
>than trying to pass the eeh_dev.
>
I'm working on explicit PE support and hopefully, I can send out
the code next week for review. The basic idea is to introuce
struct eeh_pe and attached eeh_dev to the corresponding PE. In turn,
eeh core will use PE as parameter instead of current eeh_dev ;-)
>So turning that into a list lookup will slow things down to a crawl.
>Also your patch never seems to remove anything from your list, which
>doesn't look right vs. hotplug.
>
>I suggest we fix that with a two phase approach:
>
> 1- ASAP so we can still get that into 3.4, move the eeh_dev pointer to
>struct pci_dn instead of struct device_node. This structure is
>accessible directly via dn->data and is ppc specific, that will be a
>better temporary solution and and adding stuff to the generic struct
>device_node.
>
I've sent patch again it and please take a look when you have time.
> 2- Then, what we need to do is generalize the use of eeh_dev rather
>than device_node as the main object being worked on in the eeh layer and
>thus as the argument to most functions.
>
>Cheers,
>Ben.
>
Thanks,
Gavin
>> Signed-off-by: Gavin Shan <shangw@...ux.vnet.ibm.com>
>> ---
>> arch/powerpc/include/asm/eeh.h | 7 +++++++
>> arch/powerpc/platforms/pseries/eeh_dev.c | 29 ++++++++++++++++++++++++++++-
>> include/linux/of.h | 10 ----------
>> 3 files changed, 35 insertions(+), 11 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/eeh.h b/arch/powerpc/include/asm/eeh.h
>> index d60f998..591e0a1 100644
>> --- a/arch/powerpc/include/asm/eeh.h
>> +++ b/arch/powerpc/include/asm/eeh.h
>> @@ -56,6 +56,7 @@ struct eeh_dev {
>> struct pci_controller *phb; /* Associated PHB */
>> struct device_node *dn; /* Associated device node */
>> struct pci_dev *pdev; /* Associated PCI device */
>> + struct list_head list; /* Form the global link list */
>> };
>>
>> static inline struct device_node *eeh_dev_to_of_node(struct eeh_dev *edev)
>> @@ -115,6 +116,7 @@ extern int eeh_subsystem_enabled;
>> */
>> #define EEH_MAX_ALLOWED_FREEZES 5
>>
>> +struct eeh_dev *eeh_dev_from_of_node(struct device_node *dn);
>> void * __devinit eeh_dev_init(struct device_node *dn, void *data);
>> void __devinit eeh_dev_phb_init_dynamic(struct pci_controller *phb);
>> void __init eeh_dev_phb_init(void);
>> @@ -132,6 +134,11 @@ void eeh_add_device_tree_early(struct device_node *);
>> void eeh_add_device_tree_late(struct pci_bus *);
>> void eeh_remove_bus_device(struct pci_dev *);
>>
>> +static inline struct eeh_dev *of_node_to_eeh_dev(struct device_node *dn)
>> +{
>> + return eeh_dev_from_of_node(dn);
>> +}
>> +
>> /**
>> * EEH_POSSIBLE_ERROR() -- test for possible MMIO failure.
>> *
>> diff --git a/arch/powerpc/platforms/pseries/eeh_dev.c b/arch/powerpc/platforms/pseries/eeh_dev.c
>> index f3aed7d..925d3a3 100644
>> --- a/arch/powerpc/platforms/pseries/eeh_dev.c
>> +++ b/arch/powerpc/platforms/pseries/eeh_dev.c
>> @@ -34,6 +34,7 @@
>> #include <linux/export.h>
>> #include <linux/gfp.h>
>> #include <linux/init.h>
>> +#include <linux/list.h>
>> #include <linux/kernel.h>
>> #include <linux/pci.h>
>> #include <linux/string.h>
>> @@ -41,6 +42,30 @@
>> #include <asm/pci-bridge.h>
>> #include <asm/ppc-pci.h>
>>
>> +/* eeh device list */
>> +static LIST_HEAD(eeh_dev_list);
>> +
>> +/**
>> + * eeh_dev_from_of_node - Retrieve EEH device according to OF node
>> + * @dn: OF node
>> + *
>> + * All existing eeh devices have been put into the global list.
>> + * In addition, the eeh device is tracing the corresponding
>> + * OF node. The function is used to retrieve the corresponding
>> + * eeh device according to the given OF node.
>> + */
>> +struct eeh_dev *eeh_dev_from_of_node(struct device_node *dn)
>> +{
>> + struct eeh_dev *edev = NULL;
>> +
>> + list_for_each_entry(edev, &eeh_dev_list, list) {
>> + if (edev->dn && edev->dn == dn)
>> + return edev;
>> + }
>> +
>> + return NULL;
>> +}
>> +
>> /**
>> * eeh_dev_init - Create EEH device according to OF node
>> * @dn: device node
>> @@ -62,10 +87,12 @@ void * __devinit eeh_dev_init(struct device_node *dn, void *data)
>> }
>>
>> /* Associate EEH device with OF node */
>> - dn->edev = edev;
>> edev->dn = dn;
>> edev->phb = phb;
>>
>> + /* Add to global list */
>> + list_add_tail(&edev->list, &eeh_dev_list);
>> +
>> return NULL;
>> }
>>
>> diff --git a/include/linux/of.h b/include/linux/of.h
>> index 3e710d8..a75a831 100644
>> --- a/include/linux/of.h
>> +++ b/include/linux/of.h
>> @@ -58,9 +58,6 @@ struct device_node {
>> struct kref kref;
>> unsigned long _flags;
>> void *data;
>> -#if defined(CONFIG_EEH)
>> - struct eeh_dev *edev;
>> -#endif
>> #if defined(CONFIG_SPARC)
>> char *path_component_name;
>> unsigned int unique_id;
>> @@ -75,13 +72,6 @@ struct of_phandle_args {
>> uint32_t args[MAX_PHANDLE_ARGS];
>> };
>>
>> -#if defined(CONFIG_EEH)
>> -static inline struct eeh_dev *of_node_to_eeh_dev(struct device_node *dn)
>> -{
>> - return dn->edev;
>> -}
>> -#endif
>> -
>> #if defined(CONFIG_SPARC) || !defined(CONFIG_OF)
>> /* Dummy ref counting routines - to be implemented later */
>> static inline struct device_node *of_node_get(struct device_node *node)
>
>
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