Re: [PATCH] xhci: Add BayTrail to list of Intel switchable hosts

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On Tue, 21 May 2013, Heikki Krogerus wrote:

> From: "Chew, Chiau Ee" <chiau.ee.chew@xxxxxxxxx>
> 
> Like the xHCI controller on Intel Panther Point and Lynx Point
> chipsets, the xHCI controller on Intel BayTrail has also ports that
> can be switched between the EHCI host controller.
> 
> This patch should be backported to stable kernels as old as 3.0,
> that contain commit 69e848c2090aebba5698a1620604c7dccb448684
> "Intel xhci: Support EHCI/xHCI port switching.
> 
> Signed-off-by: Chew, Chiau Ee <chiau.ee.chew@xxxxxxxxx>
> Signed-off-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
>  drivers/usb/host/ehci-pci.c   |    3 ++-
>  drivers/usb/host/pci-quirks.c |   12 +++++++++++-
>  2 files changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/host/ehci-pci.c b/drivers/usb/host/ehci-pci.c
> index 595d210..a5708d9 100644
> --- a/drivers/usb/host/ehci-pci.c
> +++ b/drivers/usb/host/ehci-pci.c
> @@ -322,7 +322,8 @@ static bool usb_is_intel_switchable_ehci(struct pci_dev *pdev)
>  		(pdev->device == 0x1E26 ||
>  		 pdev->device == 0x8C2D ||
>  		 pdev->device == 0x8C26 ||
> -		 pdev->device == 0x9C26);
> +		 pdev->device == 0x9C26 ||
> +		 pdev->device == 0x0F34);

The entries should be kept sorted in numerical order.  In fact, you 
might even interchange the 0x8C2D and 0x8C26 entries.

>  }
>  
>  static void ehci_enable_xhci_companion(void)
> diff --git a/drivers/usb/host/pci-quirks.c b/drivers/usb/host/pci-quirks.c
> index 4c338ec..6062822 100644
> --- a/drivers/usb/host/pci-quirks.c
> +++ b/drivers/usb/host/pci-quirks.c
> @@ -724,6 +724,7 @@ static int handshake(void __iomem *ptr, u32 mask, u32 done,
>  
>  #define PCI_DEVICE_ID_INTEL_LYNX_POINT_XHCI	0x8C31
>  #define PCI_DEVICE_ID_INTEL_LYNX_POINT_LP_XHCI	0x9C31
> +#define PCI_DEVICE_ID_INTEL_BYT_XHCI		0x0F35
>  
>  bool usb_is_intel_ppt_switchable_xhci(struct pci_dev *pdev)
>  {
> @@ -741,10 +742,19 @@ bool usb_is_intel_lpt_switchable_xhci(struct pci_dev *pdev)
>  		 pdev->device == PCI_DEVICE_ID_INTEL_LYNX_POINT_LP_XHCI);
>  }
>  
> +/* And so does the Intel BayTrail. */
> +bool usb_is_intel_byt_switchable_xhci(struct pci_dev *pdev)
> +{
> +	return pdev->class == PCI_CLASS_SERIAL_USB_XHCI &&
> +		pdev->vendor == PCI_VENDOR_ID_INTEL &&
> +		pdev->device == PCI_DEVICE_ID_INTEL_BYT_XHCI;
> +}
> +
>  bool usb_is_intel_switchable_xhci(struct pci_dev *pdev)
>  {
>  	return usb_is_intel_ppt_switchable_xhci(pdev) ||
> -		usb_is_intel_lpt_switchable_xhci(pdev);
> +		usb_is_intel_lpt_switchable_xhci(pdev) ||
> +		usb_is_intel_byt_switchable_xhci(pdev);
>  }
>  EXPORT_SYMBOL_GPL(usb_is_intel_switchable_xhci);

This code cries out for refactoring.  Why test pdev->class and 
pdev->vendor in the same way in three different places?  Those two 
tests should be moved directly into usb_is_intel_switchable_xhci().

The other helper functions then become simple comparisons.  As far as
I'm concerned, they also could be moved inline into
usb_is_intel_switchable_xhci().  Sarah may disagree, however.

Alan Stern

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