linux-kernel - Re: [PATCH] ohci-pci: add qemu quirk

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Date:   Tue, 14 Mar 2017 11:15:29 -0400 (EDT)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Gerd Hoffmann <kraxel@...hat.com>
cc:     linux-usb@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ohci-pci: add qemu quirk

On Tue, 14 Mar 2017, Gerd Hoffmann wrote:

> On a loaded virtualization host (dozen guests booting at the same time)
> it may happen that the ohci controller emulation doesn't manage to do
> timely frame processing, with the result that the io watchdog fires and
> considers the controller being dead, even though it's only the emulation
> being unusual slow due to the load peak.
> 
> So, add a quirk for qemu and don't use the watchdog in case we figure we
> are running on emulated ohci.  The virtual ohci controller masquerades
> as apple ohci controller, but we can identify it by subsystem id.
> 
> Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>
> ---
>  drivers/usb/host/ohci-hcd.c |  3 ++-
>  drivers/usb/host/ohci-pci.c | 16 ++++++++++++++++
>  drivers/usb/host/ohci.h     |  1 +
>  3 files changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/host/ohci-hcd.c b/drivers/usb/host/ohci-hcd.c
> index b6daf2e..b75ae28 100644
> --- a/drivers/usb/host/ohci-hcd.c
> +++ b/drivers/usb/host/ohci-hcd.c
> @@ -231,7 +231,8 @@ static int ohci_urb_enqueue (
>  
>  		/* Start up the I/O watchdog timer, if it's not running */
>  		if (!timer_pending(&ohci->io_watchdog) &&
> -				list_empty(&ohci->eds_in_use)) {
> +		    list_empty(&ohci->eds_in_use) &&
> +		    !(ohci->flags & OHCI_QUIRK_QEMU)) {

I would appreciate it if you do not change the indentation used by this 
driver.

>  			ohci->prev_frame_no = ohci_frame_no(ohci);
>  			mod_timer(&ohci->io_watchdog,
>  					jiffies + IO_WATCHDOG_DELAY);
> diff --git a/drivers/usb/host/ohci-pci.c b/drivers/usb/host/ohci-pci.c
> index bb15096..a84aebe 100644
> --- a/drivers/usb/host/ohci-pci.c
> +++ b/drivers/usb/host/ohci-pci.c
> @@ -164,6 +164,15 @@ static int ohci_quirk_amd700(struct usb_hcd *hcd)
>  	return 0;
>  }
>  
> +static int ohci_quirk_qemu(struct usb_hcd *hcd)
> +{
> +	struct ohci_hcd *ohci = hcd_to_ohci(hcd);
> +
> +	ohci->flags |= OHCI_QUIRK_QEMU;
> +	ohci_dbg(ohci, "enabled qemu quirk\n");
> +	return 0;
> +}
> +
>  /* List of quirks for OHCI */
>  static const struct pci_device_id ohci_pci_quirks[] = {
>  	{
> @@ -214,6 +223,13 @@ static int ohci_quirk_amd700(struct usb_hcd *hcd)
>  		PCI_DEVICE(PCI_VENDOR_ID_ATI, 0x4399),
>  		.driver_data = (unsigned long)ohci_quirk_amd700,
>  	},
> +	{
> +		.vendor		= PCI_VENDOR_ID_APPLE,
> +		.device		= 0x003f,
> +		.subvendor	= PCI_SUBVENDOR_ID_REDHAT_QUMRANET,
> +		.subdevice	= PCI_SUBDEVICE_ID_QEMU,
> +		.driver_data	= (unsigned long)ohci_quirk_qemu,
> +	},
>  
>  	/* FIXME for some of the early AMD 760 southbridges, OHCI
>  	 * won't work at all.  blacklist them.
> diff --git a/drivers/usb/host/ohci.h b/drivers/usb/host/ohci.h
> index 37f1725..a51b189 100644
> --- a/drivers/usb/host/ohci.h
> +++ b/drivers/usb/host/ohci.h
> @@ -418,6 +418,7 @@ struct ohci_hcd {
>  #define	OHCI_QUIRK_AMD_PLL	0x200			/* AMD PLL quirk*/
>  #define	OHCI_QUIRK_AMD_PREFETCH	0x400			/* pre-fetch for ISO transfer */
>  #define	OHCI_QUIRK_GLOBAL_SUSPEND	0x800		/* must suspend ports */
> +#define	OHCI_QUIRK_QEMU		0x1000			/* relax timing expectations */
>  
>  	// there are also chip quirks/bugs in init logic

Aside from that minor point,

Acked-by: Alan Stern <stern@...land.harvard.edu>

Alan Stern