From: dingtianhong@huawei.com (Ding Tianhong)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v9 2/4] PCI: Disable PCIe Relaxed Ordering if unsupported
Date: Wed, 9 Aug 2017 21:42:48 +0800 [thread overview]
Message-ID: <6a5b848d-1647-aa03-6af2-015b3a379adb@huawei.com> (raw)
In-Reply-To: <20170809032503.GB7191@bhelgaas-glaptop.roam.corp.google.com>
On 2017/8/9 11:25, Bjorn Helgaas wrote:
> On Tue, Aug 08, 2017 at 09:22:39PM -0500, Bjorn Helgaas wrote:
>> On Sat, Aug 05, 2017 at 03:15:11PM +0800, Ding Tianhong wrote:
>>> When bit4 is set in the PCIe Device Control register, it indicates
> After looking at the driver, I wonder if it would be simpler like
> this:
>
> int pcie_relaxed_ordering_enabled(struct pci_dev *dev)
> {
> u16 ctl;
>
> pcie_capability_read_word(dev, PCI_EXP_DEVCTL, &ctl);
> return ctl & PCI_EXP_DEVCTL_RELAX_EN;
> }
> EXPORT_SYMBOL(pcie_relaxed_ordering_enabled);
>
> static void pci_configure_relaxed_ordering(struct pci_dev *dev)
> {
> struct pci_dev *root;
>
> if (dev->is_virtfn)
> return; /* PCI_EXP_DEVCTL_RELAX_EN is RsvdP in VFs */
>
> if (!pcie_relaxed_ordering_enabled(dev))
> return;
>
> /*
> * For now, we only deal with Relaxed Ordering issues with Root
> * Ports. Peer-to-peer DMA is another can of worms.
> */
> root = pci_find_pcie_root_port(dev);
> if (!root)
> return;
>
> if (root->relaxed_ordering_broken)
> pcie_capability_clear_word(dev, PCI_EXP_DEVCTL,
> PCI_EXP_DEVCTL_RELAX_EN);
> }
>
> This doesn't check every intervening switch, but I don't think we know
> about any issues except with root ports.
>
Yes
> And the driver could do:
>
> if (!pcie_relaxed_ordering_enabled(pdev))
> adapter->flags |= ROOT_NO_RELAXED_ORDERING;
>
> The driver code wouldn't show anything about coherent memory vs.
> peer-to-peer, but we really don't have a clue about how to handle that
> yet anyway.
>
> I guess this is back to exactly what you proposed, except that I
> changed the name of pcie_relaxed_ordering_supported() to
> pcie_relaxed_ordering_enabled(), which I think is slightly more
> specific from the device's point of view.
>
OK, looks like we reach a consensus finally, I will follow your new opinion and resend, thanks.
Ding
> Bjorn
>
> .
>
next prev parent reply other threads:[~2017-08-09 13:42 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-05 7:15 [PATCH v9 0/4] Add new PCI_DEV_FLAGS_NO_RELAXED_ORDERING flag Ding Tianhong
2017-08-05 7:15 ` [PATCH v9 1/4] PCI: Add new PCIe Fabric End Node flag, PCI_DEV_FLAGS_NO_RELAXED_ORDERING Ding Tianhong
2017-08-08 23:22 ` Bjorn Helgaas
2017-08-09 1:40 ` Casey Leedom
2017-08-09 3:02 ` Bjorn Helgaas
2017-08-09 12:17 ` Ding Tianhong
2017-08-09 16:36 ` Casey Leedom
2017-08-09 15:58 ` Raj, Ashok
2017-08-09 16:46 ` Casey Leedom
2017-08-09 18:00 ` Raj, Ashok
2017-08-09 20:11 ` Casey Leedom
2017-08-05 7:15 ` [PATCH v9 2/4] PCI: Disable PCIe Relaxed Ordering if unsupported Ding Tianhong
2017-08-09 2:22 ` Bjorn Helgaas
2017-08-09 3:25 ` Bjorn Helgaas
2017-08-09 13:42 ` Ding Tianhong [this message]
2017-08-09 12:33 ` Casey Leedom
2017-08-09 13:23 ` Ding Tianhong
2017-08-05 7:15 ` [PATCH v9 3/4] net/cxgb4: Use new PCI_DEV_FLAGS_NO_RELAXED_ORDERING flag Ding Tianhong
2017-08-05 7:15 ` [PATCH v9 4/4] net/cxgb4vf: " Ding Tianhong
2017-08-07 3:47 ` [PATCH v9 0/4] Add " David Miller
2017-08-07 4:13 ` Ding Tianhong
2017-08-07 21:14 ` David Miller
2017-08-08 1:56 ` Bjorn Helgaas
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