On Fri, 2 Dec 2016, Todd Brandt wrote:
> Add a module parameter that replaces the USB_RESUME_TIMEOUT
> and other hardcoded delay numbers with the USB spec minimums.
> By default the patch retains the current values.
>
> 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 usbcore.padding=0 they are set to the
> spec minimums with no padding. The result is significant performance
> improvement in usb device resume.
>
> Signed-off-by: Todd Brandt <todd.e.brandt@xxxxxxxxxxxxxxx>
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -4237,6 +4237,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
> usbcore.blinkenlights=
> [USB] Set to cycle leds on hubs (default 0 = off).
>
> + usbcore.padding=
> + [USB] Pad the USB 2.0 spec timing values (default 1 = on).
> +
Whether or not you take Greg's suggestion and change this to a debugfs
entry, please don't call it "padding". The word is horribly imprecise
and will usually be interpreted differently from what you want.
You missed a spot on line 385 in uhci-hub.c; it should be tdrsmdn.
What happened to ohci-hub.c?
> --- a/include/linux/usb.h
> +++ b/include/linux/usb.h
> @@ -233,8 +233,30 @@ void usb_put_intf(struct usb_interface *intf);
> * In order to avoid both conditions, we're using a 40 ms resume timeout, which
> * should cope with both LPJ calibration errors and devices not following every
> * detail of the USB Specification.
> + *
> + * struct _usb_timing_config - USB timing value settings
> + * @tdrsmdn: TDRSMDN resume signal time 7.1.7.7
> + * @trsmrcy; TRSMRCY resume recovery time 7.1.7.7
> + * @trstrcy; TRSTRCY reset recovery time 7.1.7.5
> + * @name: timing config name
@name? What's that?
> + *
> + * These timing values are defined in the USB 2.0 spec sec 7.3.2 table 7-13
> + * Thir default values have been padded for various reasons and this config
> + * allows the system to use different values.
> */
> -#define USB_RESUME_TIMEOUT 40 /* ms */
> +#define USB_TIMING_TDRSMDN_MIN 20
> +#define USB_TIMING_TRSMRCY_MIN 10
> +#define USB_TIMING_TRSTRCY_MIN 0
> +#define USB_TIMING_TDRSMDN_DEF 40
> +#define USB_TIMING_TRSMRCY_DEF 10
> +#define USB_TIMING_TRSTRCY_DEF 50
> +
> +struct _usb_timing_config {
> + unsigned int tdrsmdn; /* resume signal time 20ms - infinity */
> + unsigned int trsmrcy; /* resume recovery time 0ms - 10ms */
> + unsigned int trstrcy; /* reset recovery time 0ms - infinity*/
> +};
> +extern struct _usb_timing_config usb_timing;
>
> /**
> * struct usb_interface_cache - long-term representation of a device interface
Alan Stern
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