linux-kernel - Re: [PATCH v11 6/7] PCI: Unify wait for link active into generic pci

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Date:   Sat, 24 Feb 2018 09:41:15 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Oza Pawandeep <poza@...eaurora.org>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Dongdong Liu <liudongdong3@...wei.com>,
        Keith Busch <keith.busch@...el.com>, Wei Zhang <wzhang@...com>,
        Sinan Kaya <okaya@...eaurora.org>,
        Timur Tabi <timur@...eaurora.org>
Subject: Re: [PATCH v11 6/7] PCI: Unify wait for link active into generic pci

In subject:

s/pci/PCI/

On Fri, Feb 23, 2018 at 01:54:03PM +0530, Oza Pawandeep wrote:
> Clients such as pciehp, dpc are using pcie_wait_link_active, which waits
> till the link becomes active or inactive.

Use "()" after function names so we have a visual clue that they are
functions.

> Made generic function and moved it to drivers/pci/pci.c
> 
> Signed-off-by: Oza Pawandeep <poza@...eaurora.org>
> 
> diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
> index 18a42f8..de9b0ea 100644
> --- a/drivers/pci/hotplug/pciehp_hpc.c
> +++ b/drivers/pci/hotplug/pciehp_hpc.c
> @@ -231,25 +231,11 @@ bool pciehp_check_link_active(struct controller *ctrl)
>  	return ret;
>  }
>  
> -static void __pcie_wait_link_active(struct controller *ctrl, bool active)
> +static bool pcie_wait_link_active(struct controller *ctrl)
>  {
> -	int timeout = 1000;
> -
> -	if (pciehp_check_link_active(ctrl) == active)
> -		return;
> -	while (timeout > 0) {
> -		msleep(10);
> -		timeout -= 10;
> -		if (pciehp_check_link_active(ctrl) == active)
> -			return;
> -	}
> -	ctrl_dbg(ctrl, "Data Link Layer Link Active not %s in 1000 msec\n",
> -			active ? "set" : "cleared");
> -}
> +	struct pci_dev *pdev = ctrl_dev(ctrl);
>  
> -static void pcie_wait_link_active(struct controller *ctrl)
> -{
> -	__pcie_wait_link_active(ctrl, true);
> +	return pci_wait_for_link(pdev, true);
>  }
>  
>  static bool pci_bus_check_dev(struct pci_bus *bus, int devfn)
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index f6a4dd1..f8d44b4 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -4176,6 +4176,37 @@ static int pci_pm_reset(struct pci_dev *dev, int probe)
>  	return 0;
>  }
>  
> +/**
> + * pci_wait_for_link - Wait for link till its active/inactive

s/its/it's/

> + * @pdev: Bridge device
> + * @active: waiting for active or inactive ?
> + *
> + * Use this to wait till link becomes active or inactive.
> + */
> +bool pci_wait_for_link(struct pci_dev *pdev, bool active)

I think this should be "pcie_wait_for_link()".  There's no concept of a
link in conventional PCI.

> +{
> +	int timeout = 1000;
> +	bool ret;
> +	u16 lnk_status;
> +
> +	for (;;) {
> +		pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status);
> +		ret = !!(lnk_status & PCI_EXP_LNKSTA_DLLLA);
> +		if (ret == active)
> +			return true;
> +		if (timeout <= 0)
> +			break;
> +		timeout -= 10;
> +	}
> +
> +	dev_printk(KERN_DEBUG, &pdev->dev,

pci_info().  Distros often seem to have logging configured so
KERN_DEBUG things aren't captured, and this definitely seems worth
capturing.

> +		   "Data Link Layer Link Active not %s in 1000 msec\n",
> +		   active ? "set" : "cleared");
> +
> +	return false;
> +}
> +EXPORT_SYMBOL(pci_wait_for_link);

I don't think this needs to be exported.

>  void pci_reset_secondary_bus(struct pci_dev *dev)
>  {
>  	u16 ctrl;
> diff --git a/drivers/pci/pcie/pcie-dpc.c b/drivers/pci/pcie/pcie-dpc.c
> index 5c01c63..e15bcda 100644
> --- a/drivers/pci/pcie/pcie-dpc.c
> +++ b/drivers/pci/pcie/pcie-dpc.c
> @@ -120,19 +120,9 @@ static int dpc_wait_rp_inactive(struct dpc_dev *dpc)
>  
>  static void dpc_wait_link_inactive(struct dpc_dev *dpc)
>  {
> -	unsigned long timeout = jiffies + HZ;
>  	struct pci_dev *pdev = dpc->dev->port;
> -	struct device *dev = &dpc->dev->device;
> -	u16 lnk_status;
>  
> -	pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status);
> -	while (lnk_status & PCI_EXP_LNKSTA_DLLLA &&
> -					!time_after(jiffies, timeout)) {
> -		msleep(10);
> -		pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status);
> -	}
> -	if (lnk_status & PCI_EXP_LNKSTA_DLLLA)
> -		dev_warn(dev, "Link state not disabled for DPC event\n");
> +	pci_wait_for_link(pdev, false);
>  }
>  
>  /**
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 024a1be..cb674c3 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1195,6 +1195,7 @@ int pci_add_ext_cap_save_buffer(struct pci_dev *dev,
>  int pci_request_selected_regions(struct pci_dev *, int, const char *);
>  int pci_request_selected_regions_exclusive(struct pci_dev *, int, const char *);
>  void pci_release_selected_regions(struct pci_dev *, int);
> +bool pci_wait_for_link(struct pci_dev *pdev, bool active);

I don't think this needs to be available outside the PCI core, so this
could probably be declared in drivers/pci/pci.h

>  /* drivers/pci/bus.c */
>  struct pci_bus *pci_bus_get(struct pci_bus *bus);
> -- 
> Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.,
> a Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
>