diff options
| author | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-04-10 13:45:27 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-04-10 13:45:27 +0200 |
| commit | c8d1bc12c7986c166bd3504213d9df2bc11ad7d6 (patch) | |
| tree | 9882ae7d9eb103c73029050d62232cd83328be52 /include | |
| parent | b7a4abb67416aa07cd65446dd39e64525ccfe8e5 (diff) | |
| parent | bbc78c07a51f6fd29c227b1220a9016e585358ba (diff) | |
Merge tag 'usb-for-v4.1-part2' of git://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb into usb-testing
Felipe writes:
usb: generic resume timeout for v4.1
This part 2 pull request contains only the patches
which make sure everybody on linux uses the same
resume timeout value.
Signed-off-by: Felipe Balbi <balbi@ti.com>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/usb.h | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/include/linux/usb.h b/include/linux/usb.h index 7ee1b5c3b4cb..447fe29b55b4 100644 --- a/include/linux/usb.h +++ b/include/linux/usb.h @@ -205,6 +205,32 @@ void usb_put_intf(struct usb_interface *intf); #define USB_MAXINTERFACES 32 #define USB_MAXIADS (USB_MAXINTERFACES/2) +/* + * USB Resume Timer: Every Host controller driver should drive the resume + * signalling on the bus for the amount of time defined by this macro. + * + * That way we will have a 'stable' behavior among all HCDs supported by Linux. + * + * Note that the USB Specification states we should drive resume for *at least* + * 20 ms, but it doesn't give an upper bound. This creates two possible + * situations which we want to avoid: + * + * (a) sometimes an msleep(20) might expire slightly before 20 ms, which causes + * us to fail USB Electrical Tests, thus failing Certification + * + * (b) Some (many) devices actually need more than 20 ms of resume signalling, + * and while we can argue that's against the USB Specification, we don't have + * control over which devices a certification laboratory will be using for + * certification. If CertLab uses a device which was tested against Windows and + * that happens to have relaxed resume signalling rules, we might fall into + * situations where we fail interoperability and electrical tests. + * + * 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. + */ +#define USB_RESUME_TIMEOUT 40 /* ms */ + /** * struct usb_interface_cache - long-term representation of a device interface * @num_altsetting: number of altsettings defined. |