From: Yongji Xie <xyjxie@linux.vnet.ibm.com>
To: Gavin Shan <gwshan@linux.vnet.ibm.com>
Cc: nikunj@linux.vnet.ibm.com, zhong@linux.vnet.ibm.com,
linux-doc@vger.kernel.org, aik@ozlabs.ru,
linux-pci@vger.kernel.org, corbet@lwn.net,
linux-kernel@vger.kernel.org, warrier@linux.vnet.ibm.com,
alex.williamson@redhat.com, paulus@samba.org,
bhelgaas@google.com, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v3 3/7] PCI: Do not disable memory decoding in pci_reassigndev_resource_alignment()
Date: Fri, 1 Jul 2016 14:35:04 +0800 [thread overview]
Message-ID: <a968e6af-3a17-0c79-bdfe-34329f38b2f9@linux.vnet.ibm.com> (raw)
In-Reply-To: <20160701005036.GA18999@gwshan>
Hi Gavin,
On 2016/7/1 8:50, Gavin Shan wrote:
> On Thu, Jun 30, 2016 at 06:53:09PM +0800, Yongji Xie wrote:
>> We should not disable memory decoding when we reassign alignment
>> in pci_reassigndev_resource_alignment(). It's meaningless and
>> have some side effect. For example, some fixup functions such as
>> quirk_e100_interrupt() read PCI_COMMAND_MEMORY to know whether
>> the devices has been initialized by the firmware or not. If we
>> disable memory decoding here, these functions will get a wrong
>> information that the devices was not initialized by the firmware
>> which may cause a wrong fixup. Besides, disabling memory decoding
>> may also break some devices that need to have memory decoding
>> always-on during probing.
>>
> It seems the changelog isn't correct enough if it's talking about
> below check in code:
>
> if (!(command & PCI_COMMAND_MEMORY) || !pci_resource_start(dev, 0))
> return;
Could you give me more details? It seems that we couldn't disable
e100 interrupts which enabled by some firmware if we disabling
memory decoding here.
>> Signed-off-by: Yongji Xie <xyjxie@linux.vnet.ibm.com>
>> ---
>> drivers/pci/pci.c | 8 +-------
>> 1 file changed, 1 insertion(+), 7 deletions(-)
>>
>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
>> index 6ae02de..6241cfc 100644
>> --- a/drivers/pci/pci.c
>> +++ b/drivers/pci/pci.c
>> @@ -4820,7 +4820,6 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev)
>> int i;
>> struct resource *r;
>> resource_size_t align, size;
>> - u16 command;
>>
>> /* We should never try to reassign VF's alignment */
>> if (dev->is_virtfn)
>> @@ -4838,12 +4837,7 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev)
>> return;
>> }
>>
>> - dev_info(&dev->dev,
>> - "Disabling memory decoding and releasing memory resources.\n");
>> - pci_read_config_word(dev, PCI_COMMAND, &command);
>> - command &= ~PCI_COMMAND_MEMORY;
>> - pci_write_config_word(dev, PCI_COMMAND, command);
>> -
>> + dev_info(&dev->dev, "Releasing memory resources.\n");
> Is there a problem you found with PCI_COMMAND removed? If so, could you
> please share more details, thanks.
Disabling memory decoding may break some devices which
have flag mmio_always_on. Besides the mmio_always_on case,
I also found this would break some P2P bridge such as
PEX 8718 controller.
Thanks,
Yongji
next prev parent reply other threads:[~2016-07-01 8:07 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-30 10:53 [PATCH v3 0/7] PCI: Add support for enforcing all MMIO BARs not to share PAGE_SIZE Yongji Xie
2016-06-30 10:53 ` [PATCH v3 1/7] PCI: Ignore enforced alignment when kernel uses existing firmware setup Yongji Xie
2016-07-01 0:28 ` Gavin Shan
2016-07-01 4:49 ` Yongji Xie
2016-06-30 10:53 ` [PATCH v3 2/7] PCI: Ignore enforced alignment to VF BARs Yongji Xie
2016-07-01 0:39 ` Gavin Shan
2016-07-01 5:27 ` Yongji Xie
2016-07-01 6:05 ` Gavin Shan
2016-07-01 6:40 ` Yongji Xie
2016-07-02 0:31 ` Gavin Shan
2016-06-30 10:53 ` [PATCH v3 3/7] PCI: Do not disable memory decoding in pci_reassigndev_resource_alignment() Yongji Xie
2016-07-01 0:50 ` Gavin Shan
2016-07-01 6:35 ` Yongji Xie [this message]
2016-06-30 10:53 ` [PATCH v3 4/7] PCI: Add a new option for resource_alignment to reassign alignment Yongji Xie
2016-07-01 2:25 ` Gavin Shan
2016-07-01 6:53 ` Yongji Xie
2016-06-30 10:53 ` [PATCH v3 5/7] PCI: Do not use IORESOURCE_STARTALIGN to identify bridge resources Yongji Xie
2016-07-01 2:34 ` Gavin Shan
2016-07-01 7:04 ` Yongji Xie
2016-07-02 0:37 ` Gavin Shan
2016-06-30 10:53 ` [PATCH v3 6/7] PCI: Add support for enforcing all MMIO BARs to be page aligned Yongji Xie
2016-06-30 10:53 ` [PATCH v3 7/7] PCI: Add a macro to set default alignment for all PCI devices Yongji Xie
2016-07-12 5:09 ` [PATCH v3 0/7] PCI: Add support for enforcing all MMIO BARs not to share PAGE_SIZE Yongji Xie
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