Message-ID: <20170413204800.GB28316@bhelgaas-glaptop.roam.corp.google.com>
Date:   Thu, 13 Apr 2017 15:48:00 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Sinan Kaya <okaya@...eaurora.org>
Cc:     linux-pci@...r.kernel.org, timur@...eaurora.org,
        mayurkumar.patel@...el.com, David Daney <david.daney@...ium.com>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Julia Lawall <Julia.Lawall@...6.fr>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Rajat Jain <rajatja@...gle.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH V8 3/5] PCI/ASPM: add init hook to device_add

Hi Sinan,

On Sat, Apr 08, 2017 at 12:55:49AM -0400, Sinan Kaya wrote:
> For bridges, have pcie_aspm_init_link_state() allocate a link_state,
> regardless of whether it currently has any children.
> 
> pcie_aspm_init_link_state(): Called for bridges (upstream end of
> link) after all children have been enumerated.  No longer needs to
> check aspm_support_enabled or pdev->has_secondary_link or the VIA
> quirk: pci_aspm_init() already checked that stuff, so we only need
> to check pdev->link_state here.
> 
> Now that we are calling alloc_pcie_link_state() from pci_aspm_init()
> , get rid of pci_function_0 function and detect downstream link in
> pci_aspm_init_upstream() instead when the function number is 0.
> 
> Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=194895
> Signed-off-by: Sinan Kaya <okaya@...eaurora.org>
> ---
>  drivers/pci/pcie/aspm.c | 72 ++++++++++++++++++++++++-------------------------
>  1 file changed, 36 insertions(+), 36 deletions(-)
> 
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index a80d64b..e33f84b 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -422,20 +422,6 @@ static void pcie_aspm_check_latency(struct pci_dev *endpoint)
>  	}
>  }
>  
> -/*
> - * The L1 PM substate capability is only implemented in function 0 in a
> - * multi function device.
> - */
> -static struct pci_dev *pci_function_0(struct pci_bus *linkbus)
> -{
> -	struct pci_dev *child;
> -
> -	list_for_each_entry(child, &linkbus->devices, bus_list)
> -		if (PCI_FUNC(child->devfn) == 0)
> -			return child;
> -	return NULL;
> -}
> -
>  /* Calculate L1.2 PM substate timing parameters */
>  static void aspm_calc_l1ss_info(struct pcie_link_state *link,
>  				struct aspm_register_info *upreg,
> @@ -798,7 +784,6 @@ static struct pcie_link_state *alloc_pcie_link_state(struct pci_dev *pdev)
>  	INIT_LIST_HEAD(&link->children);
>  	INIT_LIST_HEAD(&link->link);
>  	link->pdev = pdev;
> -	link->downstream = pci_function_0(pdev->subordinate);
>  
>  	/*
>  	 * Root Ports and PCI/PCI-X to PCIe Bridges are roots of PCIe
> @@ -828,11 +813,33 @@ static struct pcie_link_state *alloc_pcie_link_state(struct pci_dev *pdev)
>  
>  static int pci_aspm_init_downstream(struct pci_dev *pdev)
>  {
> +	struct pcie_link_state *link;
> +	struct pci_dev *parent;
> +
> +	/*
> +	 * The L1 PM substate capability is only implemented in function 0 in a
> +	 * multi function device.
> +	 */
> +	if (PCI_FUNC(pdev->devfn) != 0)
> +		return -EINVAL;
> +
> +	parent = pdev->bus->self;
> +	if (!parent)
> +		return -EINVAL;
> +
> +	link = parent->link_state;
> +	link->downstream = pdev;
>  	return 0;
>  }
>  
>  static int pci_aspm_init_upstream(struct pci_dev *pdev)
>  {
> +	struct pcie_link_state *link;
> +
> +	link = alloc_pcie_link_state(pdev);
> +	if (!link)
> +		return -ENOMEM;

This allocates the link_state when we enumerate a Downstream Port
instead of when we enumerate a child device.  We want the link_state
lifetime to match that of the Downstream Port, so this seems good.

But we shouldn't at the same time change the link_state deallocation
so it happens when the Downstream Port is removed, not when the child
device is removed?

>  	return 0;
>  }
>  
> @@ -843,6 +850,17 @@ static int pci_aspm_init_upstream(struct pci_dev *pdev)
>   */
>  int pci_aspm_init(struct pci_dev *pdev)
>  {
> +	if (!aspm_support_enabled)
> +		return 0;
> +
> +	if (!pci_is_pcie(pdev))
> +		return -EINVAL;
> +
> +	/* VIA has a strange chipset, root port is under a bridge */
> +	if (pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT &&
> +	    pdev->bus->self)
> +		return 0;
> +
>  	if (!pdev->has_secondary_link)
>  		return pci_aspm_init_downstream(pdev);
>  
> @@ -859,33 +877,16 @@ void pcie_aspm_init_link_state(struct pci_dev *pdev)
>  	struct pcie_link_state *link;
>  	int blacklist = !!pcie_aspm_sanity_check(pdev);
>  
> -	if (!aspm_support_enabled)
> -		return;
> -
> -	if (pdev->link_state)
> -		return;
> -
> -	/*
> -	 * We allocate pcie_link_state for the component on the upstream
> -	 * end of a Link, so there's nothing to do unless this device has a
> -	 * Link on its secondary side.
> -	 */
> -	if (!pdev->has_secondary_link)
> -		return;
> -
> -	/* VIA has a strange chipset, root port is under a bridge */
> -	if (pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT &&
> -	    pdev->bus->self)
> +	if (!pdev->link_state)
>  		return;
>  
> +	link = pdev->link_state;
>  	down_read(&pci_bus_sem);
>  	if (list_empty(&pdev->subordinate->devices))
>  		goto out;
>  
>  	mutex_lock(&aspm_lock);
> -	link = alloc_pcie_link_state(pdev);
> -	if (!link)
> -		goto unlock;
> +
>  	/*
>  	 * Setup initial ASPM state. Note that we need to configure
>  	 * upstream links also because capable state of them can be
> @@ -910,7 +911,6 @@ void pcie_aspm_init_link_state(struct pci_dev *pdev)
>  		pcie_set_clkpm(link, policy_to_clkpm_state(link));
>  	}
>  
> -unlock:
>  	mutex_unlock(&aspm_lock);
>  out:
>  	up_read(&pci_bus_sem);
> -- 
> 1.9.1
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
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