Subject: [PATCH 5/5] PCI: Rip out pci_bus_add_devices() from pci_scan_root_bus()

From: [email-masked] (Yijing Wang)
Date: Thu, 20 Nov 2014 09:14:39 +0800

On 2014/11/19 19:49, Lorenzo Pieralisi wrote:
> On Wed, Nov 19, 2014 at 07:32:49AM +0000, Yijing Wang wrote:
>> Just like pci_scan_bus(), we also should rip out
>> pci_bus_add_devices() from pci_scan_root_bus().
>> Lots platforms first call pci_scan_root_bus(), but
>> after that, they call pci_bus_size_bridges() and
>> pci_bus_assign_resources(). Place pci_bus_add_devices()
>> in pci_scan_root_bus() hurts PCI scan logic.
>> Should no functional change.
> 
> I agree with the patch, I do not agree it provides no functional change.
> You are actually fixing an issue on systems where the root bus
> is scanned at device_initcall time and pci drivers may have already been
> registered, so they end up being probed with possibly unassigned
> resources as you correctly mention in the log.
> 
> You could move the sequence:
> 
> if (!pci_has_flag(PCI_PROBE_ONLY)) {
> 	pci_bus_size_bridges();
> 	pci_bus_assign_resources();
> }
> 
> in pci_scan_root_bus() instead of taking pci_bus_add_devices() out ?

No, many drivers need additional setup before resources setup.

> 
> Would this break any code ? Or add a helper function:
> 
> pci_scan_root_bus(..., bool assign) ?

I don't think it's worth, this make scan function involved something not
scan business.

> 
> arm64 xgene code has already been fixed by reshuffling the scanning code
> sequence.
> 
> I think we should have a look at eg drivers/pci/host/pcie-xilinx.c, I
> think there is a possible initcall ordering issue there (drivers being probed
> with unassigned resources).

If pci device drivers(like network driver) are loaded before pcie host driver,
use pci_scan_root_bus() may cause problem, because pci_bus_add_devices() will
try to attach the device driver, but this time pci devices resources may not
be configured properly.

> 
> Lorenzo
> 
>>
>> Signed-off-by: Yijing Wang <[email-masked]>
>> CC: linux-alpha at vger.kernel.org
>> CC: linux-ia64 at vger.kernel.org
>> CC: linux-mips at linux-mips.org
>> CC: linux-xtensa at linux-xtensa.org
>> CC: linux-arm-kernel at lists.infradead.org
>> CC: linux-sh at vger.kernel.org
>> CC: sparclinux at vger.kernel.org
>> ---
>>  arch/alpha/kernel/pci.c          |    2 ++
>>  arch/frv/mb93090-mb00/pci-vdk.c  |    6 ++++--
>>  arch/ia64/sn/kernel/io_init.c    |    1 +
>>  arch/microblaze/pci/pci-common.c |    1 +
>>  arch/mips/pci/pci.c              |    1 +
>>  arch/mn10300/unit-asb2305/pci.c  |    5 ++++-
>>  arch/s390/pci/pci.c              |    2 +-
>>  arch/sh/drivers/pci/pci.c        |    1 +
>>  arch/sparc/kernel/leon_pci.c     |    1 +
>>  arch/tile/kernel/pci.c           |    2 ++
>>  arch/tile/kernel/pci_gx.c        |    2 ++
>>  arch/x86/pci/common.c            |    1 +
>>  arch/xtensa/kernel/pci.c         |    2 ++
>>  drivers/pci/host/pci-xgene.c     |    1 +
>>  drivers/pci/probe.c              |    1 -
>>  15 files changed, 24 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/alpha/kernel/pci.c b/arch/alpha/kernel/pci.c
>> index 076c35c..97f9730 100644
>> --- a/arch/alpha/kernel/pci.c
>> +++ b/arch/alpha/kernel/pci.c
>> @@ -334,6 +334,8 @@ common_init_pci(void)
>>  
>>  		bus = pci_scan_root_bus(NULL, next_busno, alpha_mv.pci_ops,
>>  					hose, &resources);
>> +		if (bus)
>> +			pci_bus_add_devices(bus);
>>  		hose->bus = bus;
>>  		hose->need_domain_info = need_domain_info;
>>  		next_busno = bus->busn_res.end + 1;
>> diff --git a/arch/frv/mb93090-mb00/pci-vdk.c b/arch/frv/mb93090-mb00/pci-vdk.c
>> index efa5d65..2b36044 100644
>> --- a/arch/frv/mb93090-mb00/pci-vdk.c
>> +++ b/arch/frv/mb93090-mb00/pci-vdk.c
>> @@ -316,6 +316,7 @@ void pcibios_fixup_bus(struct pci_bus *bus)
>>  
>>  int __init pcibios_init(void)
>>  {
>> +	struct pci_bus *bus;
>>  	struct pci_ops *dir = NULL;
>>  	LIST_HEAD(resources);
>>  
>> @@ -383,12 +384,13 @@ int __init pcibios_init(void)
>>  	printk("PCI: Probing PCI hardware\n");
>>  	pci_add_resource(&resources, &pci_ioport_resource);
>>  	pci_add_resource(&resources, &pci_iomem_resource);
>> -	pci_scan_root_bus(NULL, 0, pci_root_ops, NULL, &resources);
>> +	bus = pci_scan_root_bus(NULL, 0, pci_root_ops, NULL, &resources);
>>  
>>  	pcibios_irq_init();
>>  	pcibios_fixup_irqs();
>>  	pcibios_resource_survey();
>> -
>> +	if (bus)
>> +		pci_bus_add_devices(bus);
>>  	return 0;
>>  }
>>  
>> diff --git a/arch/ia64/sn/kernel/io_init.c b/arch/ia64/sn/kernel/io_init.c
>> index 0b5ce82..63b43a6 100644
>> --- a/arch/ia64/sn/kernel/io_init.c
>> +++ b/arch/ia64/sn/kernel/io_init.c
>> @@ -272,6 +272,7 @@ sn_pci_controller_fixup(int segment, int busnum, struct pci_bus *bus)
>>  		kfree(res);
>>  		kfree(controller);
>>  	}
>> +	pci_bus_add_devices(bus);
>>  }
>>  
>>  /*
>> diff --git a/arch/microblaze/pci/pci-common.c b/arch/microblaze/pci/pci-common.c
>> index 9037914..651e25d 100644
>> --- a/arch/microblaze/pci/pci-common.c
>> +++ b/arch/microblaze/pci/pci-common.c
>> @@ -1346,6 +1346,7 @@ static void pcibios_scan_phb(struct pci_controller *hose)
>>  	hose->bus = bus;
>>  
>>  	hose->last_busno = bus->busn_res.end;
>> +	pci_bus_add_devices(bus);
>>  }
>>  
>>  static int __init pcibios_init(void)
>> diff --git a/arch/mips/pci/pci.c b/arch/mips/pci/pci.c
>> index 1bf60b1..f083688 100644
>> --- a/arch/mips/pci/pci.c
>> +++ b/arch/mips/pci/pci.c
>> @@ -113,6 +113,7 @@ static void pcibios_scanbus(struct pci_controller *hose)
>>  		if (!pci_has_flag(PCI_PROBE_ONLY)) {
>>  			pci_bus_size_bridges(bus);
>>  			pci_bus_assign_resources(bus);
>> +			pci_bus_add_devices(bus);
>>  		}
>>  	}
>>  }
>> diff --git a/arch/mn10300/unit-asb2305/pci.c b/arch/mn10300/unit-asb2305/pci.c
>> index 6b4339f..860aa35 100644
>> --- a/arch/mn10300/unit-asb2305/pci.c
>> +++ b/arch/mn10300/unit-asb2305/pci.c
>> @@ -345,6 +345,7 @@ void pcibios_fixup_bus(struct pci_bus *bus)
>>   */
>>  static int __init pcibios_init(void)
>>  {
>> +	struct pci_bus *bus;
>>  	resource_size_t io_offset, mem_offset;
>>  	LIST_HEAD(resources);
>>  
>> @@ -376,11 +377,13 @@ static int __init pcibios_init(void)
>>  
>>  	pci_add_resource_offset(&resources, &pci_ioport_resource, io_offset);
>>  	pci_add_resource_offset(&resources, &pci_iomem_resource, mem_offset);
>> -	pci_scan_root_bus(NULL, 0, &pci_direct_ampci, NULL, &resources);
>> +	bus = pci_scan_root_bus(NULL, 0, &pci_direct_ampci, NULL, &resources);
>>  
>>  	pcibios_irq_init();
>>  	pcibios_fixup_irqs();
>>  	pcibios_resource_survey();
>> +	if (bus)
>> +		pci_bus_add_devices(bus);
>>  	return 0;
>>  }
>>  
>> diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c
>> index 552b990..98247f8 100644
>> --- a/arch/s390/pci/pci.c
>> +++ b/arch/s390/pci/pci.c
>> @@ -755,7 +755,7 @@ static int zpci_scan_bus(struct zpci_dev *zdev)
>>  		zpci_cleanup_bus_resources(zdev);
>>  		return -EIO;
>>  	}
>> -
>> +	pci_bus_add_devices(zdev->bus);
>>  	zdev->bus->max_bus_speed = zdev->max_bus_speed;
>>  	return 0;
>>  }
>> diff --git a/arch/sh/drivers/pci/pci.c b/arch/sh/drivers/pci/pci.c
>> index 1bc09ee..efc1051 100644
>> --- a/arch/sh/drivers/pci/pci.c
>> +++ b/arch/sh/drivers/pci/pci.c
>> @@ -69,6 +69,7 @@ static void pcibios_scanbus(struct pci_channel *hose)
>>  
>>  		pci_bus_size_bridges(bus);
>>  		pci_bus_assign_resources(bus);
>> +		pci_bus_add_devices(bus);
>>  	} else {
>>  		pci_free_resource_list(&resources);
>>  	}
>> diff --git a/arch/sparc/kernel/leon_pci.c b/arch/sparc/kernel/leon_pci.c
>> index 899b720..2971076 100644
>> --- a/arch/sparc/kernel/leon_pci.c
>> +++ b/arch/sparc/kernel/leon_pci.c
>> @@ -40,6 +40,7 @@ void leon_pci_init(struct platform_device *ofdev, struct leon_pci_info *info)
>>  
>>  		/* Assign devices with resources */
>>  		pci_assign_unassigned_resources();
>> +		pci_bus_add_devices(root_bus);
>>  	} else {
>>  		pci_free_resource_list(&resources);
>>  	}
>> diff --git a/arch/tile/kernel/pci.c b/arch/tile/kernel/pci.c
>> index 1f80a88..007466e 100644
>> --- a/arch/tile/kernel/pci.c
>> +++ b/arch/tile/kernel/pci.c
>> @@ -308,6 +308,8 @@ int __init pcibios_init(void)
>>  			pci_add_resource(&resources, &iomem_resource);
>>  			bus = pci_scan_root_bus(NULL, 0, controller->ops,
>>  						controller, &resources);
>> +			if (bus)
>> +				pci_bus_add_devices(bus);
>>  			controller->root_bus = bus;
>>  			controller->last_busno = bus->busn_res.end;
>>  		}
>> diff --git a/arch/tile/kernel/pci_gx.c b/arch/tile/kernel/pci_gx.c
>> index e39f9c5..3f8fb2c 100644
>> --- a/arch/tile/kernel/pci_gx.c
>> +++ b/arch/tile/kernel/pci_gx.c
>> @@ -889,6 +889,8 @@ int __init pcibios_init(void)
>>  		controller->first_busno = next_busno;
>>  		bus = pci_scan_root_bus(NULL, next_busno, controller->ops,
>>  					controller, &resources);
>> +		if (bus)
>> +			pci_bus_add_devices(bus);
>>  		controller->root_bus = bus;
>>  		next_busno = bus->busn_res.end + 1;
>>  	}
>> diff --git a/arch/x86/pci/common.c b/arch/x86/pci/common.c
>> index 7b20bcc..300d39e 100644
>> --- a/arch/x86/pci/common.c
>> +++ b/arch/x86/pci/common.c
>> @@ -475,6 +475,7 @@ void pcibios_scan_root(int busnum)
>>  		pci_free_resource_list(&resources);
>>  		kfree(sd);
>>  	}
>> +	pci_bus_add_devices(bus);
>>  }
>>  
>>  void __init pcibios_set_cache_line_size(void)
>> diff --git a/arch/xtensa/kernel/pci.c b/arch/xtensa/kernel/pci.c
>> index 5b34033..f2ae64e 100644
>> --- a/arch/xtensa/kernel/pci.c
>> +++ b/arch/xtensa/kernel/pci.c
>> @@ -185,6 +185,8 @@ static int __init pcibios_init(void)
>>  		pci_controller_apertures(pci_ctrl, &resources);
>>  		bus = pci_scan_root_bus(NULL, pci_ctrl->first_busno,
>>  					pci_ctrl->ops, pci_ctrl, &resources);
>> +		if (bus)
>> +			pci_bus_add_devices(bus);
>>  		pci_ctrl->bus = bus;
>>  		pci_ctrl->last_busno = bus->busn_res.end;
>>  		if (next_busno <= pci_ctrl->last_busno)
>> diff --git a/drivers/pci/host/pci-xgene.c b/drivers/pci/host/pci-xgene.c
>> index 9ecabfa..c17afe5 100644
>> --- a/drivers/pci/host/pci-xgene.c
>> +++ b/drivers/pci/host/pci-xgene.c
>> @@ -635,6 +635,7 @@ static int xgene_pcie_probe_bridge(struct platform_device *pdev)
>>  	if (!bus)
>>  		return -ENOMEM;
>>  
>> +	pci_bus_add_devices(bus);
>>  	platform_set_drvdata(pdev, port);
>>  	return 0;
>>  }
>> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
>> index 79775b5..2ab5a40 100644
>> --- a/drivers/pci/probe.c
>> +++ b/drivers/pci/probe.c
>> @@ -2084,7 +2084,6 @@ struct pci_bus *pci_scan_root_bus(struct device *parent, int bus,
>>  	if (!found)
>>  		pci_bus_update_busn_res_end(b, max);
>>  
>> -	pci_bus_add_devices(b);
>>  	return b;
>>  }
>>  EXPORT_SYMBOL(pci_scan_root_bus);
>> -- 
>> 1.7.1
>>
>> --
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> 
> .
> 

-- 
Thanks!
Yijing