linux-kernel - Re: [PATCH] PCI: Allow PCI express root ports to find themselves

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Date:   Fri, 18 Aug 2017 09:29:17 +0800
From:   Shawn Lin <shawn.lin@...k-chips.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        David Miller <davem@...emloft.net>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Ding Tianhong <dingtianhong@...wei.com>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     shawn.lin@...k-chips.com, leedom@...lsio.com, ashok.raj@...el.com,
        werner@...lsio.com, ganeshgr@...lsio.com, asit.k.mallick@...el.com,
        patrick.j.cramer@...el.com, Suravee.Suthikulpanit@....com,
        Bob.Shaw@....com, l.stach@...gutronix.de, amira@...lanox.com,
        gabriele.paoloni@...wei.com, David.Laight@...lab.com,
        jeffrey.t.kirsher@...el.com, catalin.marinas@....com,
        will.deacon@....com, mark.rutland@....com, robin.murphy@....com,
        alexander.duyck@...il.com, eric.dumazet@...il.com,
        linux-arm-kernel@...ts.infradead.org, netdev@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        linuxarm@...wei.com
Subject: Re: [PATCH] PCI: Allow PCI express root ports to find themselves

Hi

On 2017/8/17 19:06, Thierry Reding wrote:
> From: Thierry Reding <treding@...dia.com>
> 
> If the pci_find_pcie_root_port() function is called on a root port
> itself, return the root port rather than NULL.
> 
> This effectively reverts commit 0e405232871d6 ("PCI: fix oops when
> try to find Root Port for a PCI device") which added an extra check
> that would now be redundant.
> 
> Fixes: a99b646afa8a ("PCI: Disable PCIe Relaxed Ordering if unsupported")
> Fixes: c56d4450eb68 ("PCI: Turn off Request Attributes to avoid Chelsio T5 Completion erratum")
> Signed-off-by: Thierry Reding <treding@...dia.com>

Tested-by: Shawn Lin <shawn.lin@...k-chips.com>

> ---
> This applies on top of and was tested on next-20170817.
> 
> Michael, it'd be great if you could test this one again to clarify
> whether or not the fix that's already in Linus' tree is still needed, or
> whether it's indeed obsoleted by this patch.
> 
>   drivers/pci/pci.c | 9 ++++-----
>   1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index b05c587e335a..dd56c1c05614 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -514,7 +514,7 @@ EXPORT_SYMBOL(pci_find_resource);
>    */
>   struct pci_dev *pci_find_pcie_root_port(struct pci_dev *dev)
>   {
> -	struct pci_dev *bridge, *highest_pcie_bridge = NULL;
> +	struct pci_dev *bridge, *highest_pcie_bridge = dev;
>   
>   	bridge = pci_upstream_bridge(dev);
>   	while (bridge && pci_is_pcie(bridge)) {
> @@ -522,11 +522,10 @@ struct pci_dev *pci_find_pcie_root_port(struct pci_dev *dev)
>   		bridge = pci_upstream_bridge(bridge);
>   	}
>   
> -	if (highest_pcie_bridge &&
> -	    pci_pcie_type(highest_pcie_bridge) == PCI_EXP_TYPE_ROOT_PORT)
> -		return highest_pcie_bridge;
> +	if (pci_pcie_type(highest_pcie_bridge) != PCI_EXP_TYPE_ROOT_PORT)
> +		return NULL;
>   
> -	return NULL;
> +	return highest_pcie_bridge;
>   }
>   EXPORT_SYMBOL(pci_find_pcie_root_port);
>   
>