linux-kernel - Re: [PATCH 2/6] PCI: generic: Only fixup irqs for bus we are creating.

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Date:	Thu, 17 Sep 2015 10:13:21 -0700
From:	David Daney <ddaney@...iumnetworks.com>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
CC:	Will Deacon <Will.Deacon@....com>,
	David Daney <ddaney.cavm@...il.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Frank Rowand <frowand.list@...il.com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Pawel Moll <Pawel.Moll@....com>,
	Mark Rutland <Mark.Rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	David Daney <david.daney@...ium.com>
Subject: Re: [PATCH 2/6] PCI: generic: Only fixup irqs for bus we are creating.

On 09/16/2015 03:32 AM, Lorenzo Pieralisi wrote:
> On Tue, Sep 15, 2015 at 06:49:24PM +0100, David Daney wrote:
>> On 09/15/2015 10:36 AM, Will Deacon wrote:
>>> Hi David,
>>>
>>> On Sat, Sep 12, 2015 at 12:21:55AM +0100, David Daney wrote:
>>>> From: David Daney <david.daney@...ium.com>
>>>>
>>>> Use pci_walk_bus() to restrict the fixup irq actions to only the bus
>>>> being created.
>>>>
>>>> If we create multiple buses with pci-host-generic, or there are buses
>>>> created by other drivers, we don't want to call pci_fixup_irqs() which
>>>> operates on all devices, not just the devices on the bus being added.
>>>> The consequence is that either the fixups are done more than once, or
>>>> in some cases incorrect fixups could be applied.
>>>>
>>>> Signed-off-by: David Daney <david.daney@...ium.com>
>>>> ---
>>>>    drivers/pci/host/pci-host-generic.c | 8 +++++++-
>>>>    1 file changed, 7 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/pci/host/pci-host-generic.c b/drivers/pci/host/pci-host-generic.c
>>>> index 265dd25..a0fb241 100644
>>>> --- a/drivers/pci/host/pci-host-generic.c
>>>> +++ b/drivers/pci/host/pci-host-generic.c
>>>> @@ -205,6 +205,12 @@ static int gen_pci_parse_map_cfg_windows(struct gen_pci *pci)
>>>>    	return 0;
>>>>    }
>>>>
>>>> +static int gen_pci_fixup_irq_cb(struct pci_dev *dev, void *arg)
>>>> +{
>>>> +	pdev_fixup_irq(dev, pci_common_swizzle, of_irq_parse_and_map_pci);
>>>> +	return 0;
>>>> +}
>>>> +
>>>>    static int gen_pci_probe(struct platform_device *pdev)
>>>>    {
>>>>    	int err;
>>>> @@ -262,7 +268,7 @@ static int gen_pci_probe(struct platform_device *pdev)
>>>>    		return -ENODEV;
>>>>    	}
>>>>
>>>> -	pci_fixup_irqs(pci_common_swizzle, of_irq_parse_and_map_pci);
>>>> +	pci_walk_bus(bus, gen_pci_fixup_irq_cb, NULL);
>>>
>>> Any chance we could put something in the core PCI code for this? I think
>>> any host controller wanting to work with arm64 is potentially going to
>>> run into the same problem.
>>
>> Good idea.
>>
>> I will move the walking code into setup-irq.c (the current home of
>> pci_fixup_irqs()), and make it part of patch 1/6.
>
> For arm64 we could even compile out pci_fixup_irqs() since the IRQ mapping
> is done in pcibios_add_device() through DT, I agree on CONFIG_ARM this
> needs fixing though, so yes, make it common code and patch all host
> controllers that make use of pci_fixup_irqs() since that's a common
> issue as far as I can see (ARM pcibios works around it by having a
> IRQ mapping function per bus and it provides an API to initialize
> multiple host controllers at once and fixing up IRQs before devices
> are added, still, for host controllers that do not use that
> functionality - eg drivers/pci/host/pcie-designware.c - if there are
> multiple host controllers instances we run into the same problem).

Patching up other PCI bus drivers would be deferred to a different patch 
set, as I have no way to test it.

>
> Side note: do you have any PCI host controller where mapping IRQs through
> of_irq_parse_and_map_pci() does not work ? If yes, why ?
>

The of_irq_parse_and_map_pci() call in arch/arm64/kernel/pci.c 
(pcibios_add_device) seems to work for me.

I did send a patch recently to make it quite emitting erroneous error 
messages for PCI devices that have no irq pin.

David Daney
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