linux-kernel - Re: [PATCH v2 1/8] pci: Create pci_reset_bridge_secondary

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Message-ID: <518AA420.5020900@redhat.com>
Date:	Wed, 08 May 2013 15:14:40 -0400
From:	Don Dutile <ddutile@...hat.com>
To:	Alex Williamson <alex.williamson@...hat.com>
CC:	bhelgaas@...gle.com, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/8] pci: Create pci_reset_bridge_secondary_bus()

On 05/07/2013 10:57 PM, Alex Williamson wrote:
> Move the secondary bus reset code from pci_parent_bus_reset() into its own
> function.  Export it as we'll later be calling it from hotplug controllers.
>
> Signed-off-by: Alex Williamson<alex.williamson@...hat.com>
> ---
>   drivers/pci/pci.c   |   32 +++++++++++++++++++++++---------
>   include/linux/pci.h |    1 +
>   2 files changed, 24 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index b099e00..d0f313f 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -3210,9 +3210,30 @@ static int pci_pm_reset(struct pci_dev *dev, int probe)
>   	return 0;
>   }
>
> -static int pci_parent_bus_reset(struct pci_dev *dev, int probe)
> +/**
> + * pci_reset_bridge_secondary_bus - Reset the secondary bus on a PCI bridge.
> + * @dev: Bridge device
> + *
> + * Use the bridge control register to assert reset on the secondary bus.
> + * Devices on the secondary bus are left in power-on state.
> + */
> +void pci_reset_bridge_secondary_bus(struct pci_dev *dev)
see recommended api change below...

>   {
>   	u16 ctrl;
> +
> +	pci_read_config_word(dev, PCI_BRIDGE_CONTROL,&ctrl);
> +	ctrl |= PCI_BRIDGE_CTL_BUS_RESET;
> +	pci_write_config_word(dev, PCI_BRIDGE_CONTROL, ctrl);
> +	msleep(100);
> +
> +	ctrl&= ~PCI_BRIDGE_CTL_BUS_RESET;
> +	pci_write_config_word(dev, PCI_BRIDGE_CONTROL, ctrl);
> +	msleep(100);
> +}
> +EXPORT_SYMBOL_GPL(pci_reset_bridge_secondary_bus);
> +
> +static int pci_parent_bus_reset(struct pci_dev *dev, int probe)
> +{
>   	struct pci_dev *pdev;
>
>   	if (pci_is_root_bus(dev->bus) || dev->subordinate || !dev->bus->self)
> @@ -3225,14 +3246,7 @@ static int pci_parent_bus_reset(struct pci_dev *dev, int probe)
>   	if (probe)
>   		return 0;
>
> -	pci_read_config_word(dev->bus->self, PCI_BRIDGE_CONTROL,&ctrl);
> -	ctrl |= PCI_BRIDGE_CTL_BUS_RESET;
> -	pci_write_config_word(dev->bus->self, PCI_BRIDGE_CONTROL, ctrl);
> -	msleep(100);
> -
> -	ctrl&= ~PCI_BRIDGE_CTL_BUS_RESET;
> -	pci_write_config_word(dev->bus->self, PCI_BRIDGE_CONTROL, ctrl);
> -	msleep(100);
> +	pci_reset_bridge_secondary_bus(dev->bus->self);
>
It makes more sense to pass the pci-bus struct of the bus you want to reset,
instead of the pdev of the bridge that bus is sourced by.
i.e, dev->bus,  and above, extract the pdev from the bus-struct.
That way, devices asking for bus-reset, don't have to know the bus-struct details
to make the call right... just their own pdev->bus reference.
(more object-like/clean).

>   	return 0;
>   }
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 710067f..695620c 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -905,6 +905,7 @@ int pcie_set_mps(struct pci_dev *dev, int mps);
>   int __pci_reset_function(struct pci_dev *dev);
>   int __pci_reset_function_locked(struct pci_dev *dev);
>   int pci_reset_function(struct pci_dev *dev);
> +void pci_reset_bridge_secondary_bus(struct pci_dev *dev);
and final tweak.

>   void pci_update_resource(struct pci_dev *dev, int resno);
>   int __must_check pci_assign_resource(struct pci_dev *dev, int i);
>   int __must_check pci_reassign_resource(struct pci_dev *dev, int i, resource_size_t add_size, resource_size_t align);
>
> --
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