On 9/10/2021 8:08 PM, Thinh Nguyen wrote: > Wesley Cheng wrote: >> >> >> On 9/9/2021 6:15 PM, Thinh Nguyen wrote: >>> Jack Pham wrote: >>>> Some functions may dynamically enable and disable their endpoints >>>> regularly throughout their operation, particularly when Set Interface >>>> is employed to switch between Alternate Settings. For instance the >>>> UAC2 function has its respective endpoints for playback & capture >>>> associated with AltSetting 1, in which case those endpoints would not >>>> get enabled until the host activates the AltSetting. And they >>>> conversely become disabled when the interfaces' AltSetting 0 is >>>> chosen. >>>> >>>> With the DWC3 FIFO resizing algorithm recently added, every >>>> usb_ep_enable() call results in a call to resize that EP's TXFIFO, >>>> but if the same endpoint is enabled again and again, this incorrectly >>>> leads to FIFO RAM allocation exhaustion as the mechanism did not >>>> account for the possibility that endpoints can be re-enabled many >>>> times. >>>> >>>> Example log splat: >>>> >>>> dwc3 a600000.dwc3: Fifosize(3717) > RAM size(3462) ep3in depth:217973127 >>>> configfs-gadget gadget: u_audio_start_capture:521 Error! >>>> dwc3 a600000.dwc3: request 000000000be13e18 was not queued to ep3in >>>> >>>> This is easily fixed by bailing out of dwc3_gadget_resize_tx_fifos() >>>> if an endpoint is already resized, avoiding the calculation error >>>> resulting from accumulating the EP's FIFO depth repeatedly. >>>> >>>> Fixes: 9f607a309fbe9 ("usb: dwc3: Resize TX FIFOs to meet EP bursting requirements") >>>> Signed-off-by: Jack Pham <jackp@xxxxxxxxxxxxxx> >>>> --- >>>> drivers/usb/dwc3/gadget.c | 4 ++++ >>>> 1 file changed, 4 insertions(+) >>>> >>>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c >>>> index 804b50548163..c647c76d7361 100644 >>>> --- a/drivers/usb/dwc3/gadget.c >>>> +++ b/drivers/usb/dwc3/gadget.c >>>> @@ -747,6 +747,10 @@ static int dwc3_gadget_resize_tx_fifos(struct dwc3_ep *dep) >>>> if (!usb_endpoint_dir_in(dep->endpoint.desc) || dep->number <= 1) >>>> return 0; >>>> >>>> + /* bail if already resized */ >>>> + if (dwc3_readl(dwc->regs, DWC3_GTXFIFOSIZ(dep->number >> 1))) >>>> + return 0; >>>> + >>>> ram1_depth = DWC3_RAM1_DEPTH(dwc->hwparams.hwparams7); >>>> >>>> if ((dep->endpoint.maxburst > 1 && >>>> >> >> Hi Thinh, >> >>> >>> This seems like a workaround more than a fix. As previously pointed out, >>> there will be problems when there are multiple alternate setting >>> interface [2]. If we're doing this way, are we properly allocating the >>> fifo size for the alternate setting that requires the most fifo size and >>> not just the first alt-setting 0? Also different alt-setting can have >> >> Each alt interface will call usb_ep_autoconfig() which should be >> assigned different endpoint numbers. This would mean that if alt intf#0 >> gets selected, and EP is enabled, then we will resize the TXFIFO and map >> that FIFO to the physical EP. Then when/if the host requests the other >> alt intf#1, and that calls EP enable, then the logic will then attempt >> to resize based on the parameters, and again map that FIFO to the >> physical EP. (since we call autoconfig on all interfaces, they should be >> assigned different endpoints) Hi Thinh, > > That's not true. Different alt-settings of an interface can share > endpoint numbers. This is often the case for UASP driver where > alt-setting 0 is for BOT protocol and alt-setting 1 is UASP. When we > switch alt-setting, we disable the current endpoints and enable the > old/new ones. > Thanks for pointing that use case out. Maybe we can consider seeing if we can walk through all alternate interfaces for a particular function, and resize for the largest setting? That might be a possible improvement made to the check_config() function. Let me start makign the changes for this and verifying it. >> >> I agree that there is currently a limitation because we are going to >> reserve at minimum 1 FIFO for BOTH alt interfaces, even though there is >> only 1 interface active at a time. The missing logic that we might be >> missing is seeing how we can re-purpose the FIFO that is being disabled. >> However, I think Jack's fix here would be applicable to the improvement >> in logic to re-use/re-assign FIFO space allocated by disabled EPs also. >> > > Improvement is always great. I just hope we don't just stop where we are > now. Since you're working on this feature at the moment, it would be > good to also resolve some of the outstanding issues as Jack's fix seems > to be incomplete. > If we implement the improvement mentioned above, I think Jack's fix will be applicable there as well. If we resize for the largest alternate interface, then there would be no reason for us to resize again. >>> different endpoints, the logic handling this may not be simple. >>> >>> There are a few review comments for Wesley. Hopefully they get resolved >>> eventually. >> >> As mentioned above, there is a lot of considerations we need to make >> when looking at the amount of combinations that can be done for a USB >> configuration. We obviously want to see if we can find a way to >> re-allocate FIFO space, but it gets complicated if we run into a >> "fragmented" situation where the RAM associated to the EP being >> re-allocated is in between 2 that are active. >> > > I'd like to have this feature added, and it would be great if it can > overcome some of the current limitations. At the moment, if this feature > is enabled, it may improve some applications, but it may also cause > regression for some. As I noted, the fix may not be simple, but I hope > this feature can work for various applications and not just a limited few. > Agreed, there are some use cases that we may not consider in our platform, so I appreciate the input. Thanks Wesley Cheng -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project