On Wed, 14 Dec 2016, Todd Brandt wrote:
> Add a kernel parameter that replaces the USB_RESUME_TIMEOUT
> and other hardcoded delay numbers with the USB spec minimums.
>
> The USB subsystem currently uses heavily padded values for TDRSMDN
> and TRSTRCY. This patch keeps the current values by default, but if
> the kernel is booted with usb_timing_minimum=1 they are set to the
> spec minimums with no padding. The result is significant performance
> improvement in usb device resume.
>
> Example analyze_suspend runs are provided here showing the benefits:
> https://01.org/suspendresume/blogs/tebrandt/2016/usb-resume-optimization-using-spec-minimum-delays
>
> Signed-off-by: Todd Brandt <todd.e.bra...@linux.intel.com>
...
> --- a/drivers/usb/common/common.c
> +++ b/drivers/usb/common/common.c
> @@ -19,6 +19,13 @@
> #include <linux/usb/otg.h>
> #include <linux/of_platform.h>
>
> +struct _usb_timing_config usb_timing = {
Initial '_'? Ugh. How about just struct usb_timing_config?
> + .tdrsmdn = USB_TIMING_TDRSMDN_DEF,
> + .trsmrcy = USB_TIMING_TRSMRCY_DEF,
> + .trstrcy = USB_TIMING_TRSTRCY_DEF
> +};
> +EXPORT_SYMBOL_GPL(usb_timing);
> --- a/drivers/usb/host/uhci-hub.c
> +++ b/drivers/usb/host/uhci-hub.c
> @@ -339,7 +339,7 @@ static int uhci_hub_control(struct usb_hcd *hcd, u16
> typeReq, u16 wValue,
>
> /* USB v2.0 7.1.7.5 */
> uhci->ports_timeout = jiffies +
> - msecs_to_jiffies(USB_RESUME_TIMEOUT);
> + msecs_to_jiffies(usb_timing.trstrcy);
Actually this was wrong from the beginning (it was a bug). It should
be 50 ms (TDRSTR), not TRSTRCY. I suppose that could be fixed in a
separate patch.
Alan Stern
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