On Wed, Sep 06, 2023 at 12:44:02AM +0000, Thinh Nguyen wrote:
On Mon, Sep 04, 2023, Michael Grzeschik wrote:Cc'ing: Stanley Chang <stanley_chang@xxxxxxxxxxx> On Mon, Sep 04, 2023 at 12:41:33AM +0200, Michael Grzeschik wrote: > Hi Thinh > > On Fri, Sep 01, 2023 at 01:35:16AM +0000, Thinh Nguyen wrote: > > On Fri, Sep 01, 2023, Michael Grzeschik wrote: > > > I just stumbled over a similar issue we already solved for the High > > > Speed Case when streaming ISOC packages and using a multiplier higher > > > then one. Last time we saw some bad frame artefacts when using the > > > higher multiplier value. The Frames were distorted due to truncated > > > transfers. > > > > > > Since the last case we have patch > > > > > > 8affe37c525d ("usb: dwc3: gadget: fix high speed multiplier setting") > > > > > > that fixes the calculation of the mult PCM1 parameter when using high > > > speed transfers. After that no truncations were reported again. > > > > > > However I came across a similar issue which is just a little less easy > > > to trigger and only occurs with Superspeed. Now, while the memory > > > bandwidth of the machine runs on higher load, the UVC frames are > > > similarly distorted when we use a multiplier higher then one. > > > > > > I looked over the implications the multiplier has on the Superspeed case > > > in the dwc3 gadget driver, but could only find some TXFIFO adjustments > > > and no other extra bits e.g. in the transfer descriptors. Do you have > > > some pointers how the multiplier parameter of the endpoint is used in > > > hardware? > > > > > > > As you already know, PCM1 is only for highspeed not Superspeed. What > > failure did the dwc3 driver reported? Missed isoc? What's the request > > transfer size? > > Yes, I see missed isoc errors. But this is just a symptom in this case. > > I can increase the maxburst or maxpacket parameters stepwise and on > one point see the flickering appear. But when I increase the TXFIFOSIZE > for the endpoint the flickering is gone again. Until I increase one of > the parameters maxpacket or maxburst to much again. > > So due to the memory bandwidth is under pressure, it seems like the > hardware is not fast enough with sending the expected data per transfer, > due to the txfifo is not long enough and needs to be refilled more > often. > > This sounds like a fifo underrun issue in the hardware. This whole issue sound like a case of stanleys patches: https://lore.kernel.org/all/20230828055212.5600-1-stanley_chang@xxxxxxxxxxx/ For now I was unluky while adjusting the paramaters. Are those registers anywhere documented?How does his change impact isoc endpoint? His change should only affect non-periodic endpoint. Also periodic settings is only for host.
Since I did not find proper documentation of the registers I was just hoping. In the device-tree documentation stanley added he mentioned some device mode properties. As I look again it seems the RXFIFO parameters are the only one affecting device mode. So nevermind. Thanks, Michael -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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