[PATCH RFC v4 2/9] powerpc/powernv/pci: Suppress an EEH error when reading an empty slot

[Sergey Miroshnichenko]

On 3/5/19 9:14 AM, Oliver wrote:
> On Sat, Mar 2, 2019 at 3:04 AM Sergey Miroshnichenko
> <s.miroshnichenko at yadro.com> wrote:
>>
>> Reading an empty slot returns all ones, which triggers a false
>> EEH error event on PowerNV. This patch unfreezes the bus where
>> it has happened.
>>
>> Signed-off-by: Sergey Miroshnichenko <s.miroshnichenko at yadro.com>
>> ---
>>  arch/powerpc/include/asm/ppc-pci.h   |  1 +
>>  arch/powerpc/kernel/pci_dn.c         |  2 +-
>>  arch/powerpc/platforms/powernv/pci.c | 34 ++++++++++++++++++++++++----
>>  3 files changed, 32 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/ppc-pci.h b/arch/powerpc/include/asm/ppc-pci.h
>> index f67da277d652..737393c54f58 100644
>> --- a/arch/powerpc/include/asm/ppc-pci.h
>> +++ b/arch/powerpc/include/asm/ppc-pci.h
>> @@ -40,6 +40,7 @@ void *traverse_pci_dn(struct pci_dn *root,
>>                       void *(*fn)(struct pci_dn *, void *),
>>                       void *data);
>>  extern void pci_devs_phb_init_dynamic(struct pci_controller *phb);
>> +struct pci_dn *pci_bus_to_pdn(struct pci_bus *bus);
>>
>>  /* From rtas_pci.h */
>>  extern void init_pci_config_tokens (void);
>> diff --git a/arch/powerpc/kernel/pci_dn.c b/arch/powerpc/kernel/pci_dn.c
>> index ab147a1909c8..341ed71250f1 100644
>> --- a/arch/powerpc/kernel/pci_dn.c
>> +++ b/arch/powerpc/kernel/pci_dn.c
>> @@ -40,7 +40,7 @@
>>   * one of PF's bridge. For other devices, their firmware
>>   * data is linked to that of their bridge.
>>   */
>> -static struct pci_dn *pci_bus_to_pdn(struct pci_bus *bus)
>> +struct pci_dn *pci_bus_to_pdn(struct pci_bus *bus)
>>  {
>>         struct pci_bus *pbus;
>>         struct device_node *dn;
>> diff --git a/arch/powerpc/platforms/powernv/pci.c b/arch/powerpc/platforms/powernv/pci.c
>> index 3260250d2029..73c2d0aed996 100644
>> --- a/arch/powerpc/platforms/powernv/pci.c
>> +++ b/arch/powerpc/platforms/powernv/pci.c
>> @@ -761,6 +761,21 @@ static inline pnv_pci_cfg_check(struct pci_dn *pdn)
>>  }
>>  #endif /* CONFIG_EEH */
>>
>> +static int get_bus_pe_number(struct pci_bus *bus)
>> +{
>> +       struct pci_dn *pdn = pci_bus_to_pdn(bus);
>> +       struct pci_dn *child;
>> +
>> +       if (!pdn)
>> +               return IODA_INVALID_PE;
>> +
>> +       list_for_each_entry(child, &pdn->child_list, list)
>> +               if (child->pe_number != IODA_INVALID_PE)
>> +                       return child->pe_number;
>> +
>> +       return IODA_INVALID_PE;
>> +}
>> +
>>  static int pnv_pci_read_config(struct pci_bus *bus,
>>                                unsigned int devfn,
>>                                int where, int size, u32 *val)
>> @@ -769,12 +784,23 @@ static int pnv_pci_read_config(struct pci_bus *bus,
>>         struct pci_controller *hose = pci_bus_to_host(bus);
>>         struct pnv_phb *phb = hose->private_data;
>>         int ret;
>> +       u32 empty_val = 0xFFFFFFFF;
>>
>> -       *val = 0xFFFFFFFF;
>> +       *val = empty_val;
>>         pdn = pci_get_pdn_by_devfn(bus, devfn);
>> -       if (!pdn)
>> -               return pnv_pci_cfg_read_raw(phb->opal_id, bus->number, devfn,
>> -                                           where, size, val);
>> +       if (!pdn) {
>> +               int pe_number = get_bus_pe_number(bus);
>> +
>> +               ret = pnv_pci_cfg_read_raw(phb->opal_id, bus->number, devfn,
>> +                                          where, size, val);
>> +
>> +               if (!ret && (*val == empty_val) && phb->unfreeze_pe)
> 
> Do this empty val check work when using 1 or 2 byte cfg accesses?
> 

That was intentional because 0xff and 0xffff are valid values, but the
0xffffffff is the only reliable sign of an empty slot. And the kernel
pokes a slot by the pci_bus_generic_read_dev_vendor_id() function, which
in turn tries to pci_bus_read_config_dword(PCI_VENDOR_ID).

But I haven't tried actually to read 1-2 bytes from an empty slot to
test if that triggers an EEH. If it does, I'll change that to
EEH_IO_ERROR_VALUE(size).

>> +                       phb->unfreeze_pe(phb, (pe_number == IODA_INVALID_PE) ?
>> +                                        0xff : pe_number,
> 
> Use phb->ioda.reserved_pe_idx rather than guessing that 0xff is safe
> to use. On P9 we have PHBs with 512 PEs and some older P8 firmware
> releases used 0 as the reserved PE rather than 0xff.
> 

Thanks for the catch! I'll fix that in v5.

Best regards,
Serge

>> +                                        OPAL_EEH_ACTION_CLEAR_FREEZE_ALL);
>> +
>> +               return ret;
>> +       }
>>
>>         if (!pnv_pci_cfg_check(pdn))
>>                 return PCIBIOS_DEVICE_NOT_FOUND;
>> --
>> 2.20.1
>>

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