On Wed, 31 Aug 2016, Felipe Balbi wrote:
> Hi John,
>
> John Youn <John.Youn@xxxxxxxxxxxx> writes:
> > On 8/31/2016 2:38 AM, Felipe Balbi wrote:
> >> If we don't know what are the actual U1/U2 exit
> >> latencies from the UDC, we're better off using
> >> maximum latencies as default. This should avoid
> >> any problems with too frequent U1/U2 entry.
> >>
> >> Signed-off-by: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>
> >> ---
> >> include/linux/usb/gadget.h | 12 ++++++++++--
> >> 1 file changed, 10 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
> >> index 3667d667cab1..20cb590c658e 100644
> >> --- a/include/linux/usb/gadget.h
> >> +++ b/include/linux/usb/gadget.h
> >> @@ -276,11 +276,19 @@ static inline void usb_ep_fifo_flush(struct usb_ep *ep)
> >>
> >> /*-------------------------------------------------------------------------*/
> >>
> >> +/**
> >> + * struct usb_dcd_config_params - Default U1/U2 exit latencies
> >> + * @bU1DevExitLat: U1 Exit Latency in us
> >> + * @bU2DevExitLat: U2 Exit Latency in us
> >> + *
> >> + * Note that we will be setting U1/U2 exit latencies to their maximum
> >> + * by default if no value is passed by the UDC Driver.
> >> + */
> >> struct usb_dcd_config_params {
> >> __u8 bU1DevExitLat; /* U1 Device exit Latency */
> >> -#define USB_DEFAULT_U1_DEV_EXIT_LAT 0x01 /* Less then 1 microsec */
> >> +#define USB_DEFAULT_U1_DEV_EXIT_LAT 10 /* us */
> >> __le16 wU2DevExitLat; /* U2 Device exit Latency */
> >> -#define USB_DEFAULT_U2_DEV_EXIT_LAT 0x1F4 /* Less then 500 microsec */
> >> +#define USB_DEFAULT_U2_DEV_EXIT_LAT 2047 /* us */
> >> };
> >>
> >>
> >>
> >
> > Hi Felipe,
> >
> > Speaking of this, how would you feel about adding module parameters in
> > the dwc3-pci to set these? And we also have several more settings in
> > our internal tree that we need for IP validation and debugging.
> >
> > As you know the IP is highly configurable, and we do much of the
> > testing against these configurations via software settings. And our
> > validation platform is not a typical platform. Basically we have a
> > single platform, but the instantiated IP and PHY could be configured
> > in any way so it could need different values passed in for
> > testing. Like the U1/U2 exit latencies, LPM NYET threshold, HIRD,
> > USB2/3 SUSPHY, LPM sleep mode, GFLADJ, etc.
> >
> > And some things that are automatically detected we need to restrict or
> > disable to get full coverage. Such as disabling U1/U2 and LPM, maximum
> > speed, dr_mode, NUMP, RX thresholding, RX thresholding packet count.
> >
> > I know module parameters are typically frowned upon so do you
> > recommend another approach?
>
> I completely understand the situation. Module parameters are, well,
> rather unsophisticated. FPGA validation is, however, a 'peculiar' use
> case.
>
> I want to avoid module parameters as much as possible, but apart from
> module parameters, the only thing I can think of is a specific
> sub-directory on debugfs which only gets compile if EXPERT &&
> DWC3_VALIDATION_MODE or whatever.
>
> Would debugfs work for you? The only problem is for things which get
> discovered during probe()
>
> It's an odd situation; whatever we do, I'd still like to be able to
> connect two HAPS DX to the same desktop (as PCIe cards) and validate
> both with different parameters.
>
> I'm open for suggestions which don't involve module parameters :-)
>
> Greg? Alan? Anybody?
debugfs seems like a good compromise. At least it does offer the
ability to set different values for different controllers. The
disadvantage is that you can't set the values right at probe time. For
testing that doesn't matter, but it might be important for actual use.
(Come to think of it, I don't know of any reasonable way to make
different values available for different controllers at probe time.
Specifying a controller ID or address along with the values in a module
parameter is not reasonable.)
Alan Stern
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