Felipe,
On Tue, Nov 20, 2018 at 11:16 PM Minas Harutyunyan minas.harutyunyan@synopsys.com wrote:
On 11/14/2018 3:30 AM, Doug Anderson wrote:
Hi,
On Sun, Sep 9, 2018 at 9:24 PM Terin Stock terin@terinstock.com wrote:
Modify the wait delay utilize the high resolution timer API to allow for more precisely scheduled callbacks.
A previous commit added a 1ms retry delay after multiple consecutive NAKed transactions using jiffies. On systems with a low timer interrupt frequency, this delay may be significantly longer than specified, resulting in misbehavior with some USB devices.
This scenario was reached on a Raspberry Pi 3B with a Macally FDD-USB floppy drive (identified as 0424:0fdc Standard Microsystems Corp. Floppy, based on the USB97CFDC USB FDC). With the relay delay, the drive would be unable to mount a disk, replying with NAKs until the device was reset.
Using ktime, the delta between starting the timer (in dwc2_hcd_qh_add) and the callback function can be determined. With the original delay implementation, this value was consistently approximately 12ms. (output in us).
<idle>-0 [000] ..s. 1600.559974: dwc2_wait_timer_fn: wait_timer delta: 11976 <idle>-0 [000] ..s. 1600.571974: dwc2_wait_timer_fn: wait_timer delta: 11977 <idle>-0 [000] ..s. 1600.583974: dwc2_wait_timer_fn: wait_timer delta: 11976 <idle>-0 [000] ..s. 1600.595974: dwc2_wait_timer_fn: wait_timer delta: 11977After converting the relay delay to using a higher resolution timer, the delay was much closer to 1ms.
<idle>-0 [000] d.h. 1956.553017: dwc2_wait_timer_fn: wait_timer delta: 1002 <idle>-0 [000] d.h. 1956.554114: dwc2_wait_timer_fn: wait_timer delta: 1002 <idle>-0 [000] d.h. 1957.542660: dwc2_wait_timer_fn: wait_timer delta: 1004 <idle>-0 [000] d.h. 1957.543701: dwc2_wait_timer_fn: wait_timer delta: 1002The floppy drive operates properly with delays up to approximately 5ms, and sends NAKs for any delays that are longer.
Fixes: 38d2b5fb75c1 ("usb: dwc2: host: Don't retry NAKed transactions right away") Signed-off-by: Terin Stock terin@terinstock.com
drivers/usb/dwc2/hcd.h | 2 +- drivers/usb/dwc2/hcd_queue.c | 19 ++++++++++++------- 2 files changed, 13 insertions(+), 8 deletions(-)
Reviewed-by: Douglas Anderson dianders@chromium.org Cc: stable@vger.kernel.org
Acked-by: Minas Harutyunyan hminas@synopsys.com
It looks like Terin missed CCing you on the original patch. I assume you are still picking up dwc2 changes like this? If so, should he resend the patch targeting you (and including Minas and my tags) or do you want to pick it up from one of the mailing lists he CCed?
Thanks!
-Doug