Dne 27. 05. 21 v 15:47 Stefan Wahren napsal(a): >> I think I see the problem. >> >> IIUC the calculations and checks, all g-tx-fifo-size values + >> g-rx-fifo-size + g-np-tx-fifo-size must not exceed total_fifo_size. My >> RPi4 reports the total_fifo_size as 4080 (in >> /sys/kernel/debug/usb/fe980000.usb/hw_params). >> >> Linux mainline >> https://github.com/torvalds/linux/search?p=3&q=g-tx-fifo-size : >> >> The increase in value of g-rx-fifo-size exceeds the limit for the DTSI >> files we patched: >> >> Both bcm283x-rpi-usb-peripheral.dtsi and bcm283x-rpi-usb-otg.dtsi: >> 558 + 32 + 256 + 256 + 512 + 512 + 512 + 768 + 768 = 4174 > 4080 >> >> while the sum with the previous value of 256 reached just 3872 < 4080. >> >> >> The raspberrypi repo >> https://github.com/raspberrypi/linux/search?q=g-tx-fifo-size : >> >> It has a different mix of the DTSI files >> dwc2-overlay.dts >> upstream-overlay.dts >> upstream-pi4-overlay.dts > yes these overlay files are vendor specific and doesn't exist in > mainline. The upstream*dts were intended to "simulate" mainline > behavior, but unfortunately differ in this case. >> >> all of which define >> g-tx-fifo-size = <512 512 512 512 512 256 256>; >> >> Here the calculation holds: >> 558 + 32 + 512 + 512 + 512 + 512 + 512 + 256 + 256 = 3662 < 4080 >> >> My RPi4 uses one of these DTSIs, because my >> /sys/kernel/debug/usb/fe980000.usb/params says: >> >> g_rx_fifo_size : 558 >> g_np_tx_fifo_size : 32 >> g_tx_fifo_size[0] : 0 >> g_tx_fifo_size[1] : 512 >> g_tx_fifo_size[2] : 512 >> g_tx_fifo_size[3] : 512 >> g_tx_fifo_size[4] : 512 >> g_tx_fifo_size[5] : 512 >> g_tx_fifo_size[6] : 256 >> g_tx_fifo_size[7] : 256 >> >> >> IIUC the tx_fifo values in bcm283x-rpi-usb-peripheral.dtsi and >> bcm283x-rpi-usb-otg.dtsi files can be lowered to the values used and >> tested (at least by me) in the RPi repo. But this is outside of my >> knowledge, honestly I do not know what is the most appropriate >> distribution of the remaining fifo space among the g_tx_fifo buffers. >> Please can the RPi developers (Phil?) suggest a fix? > > As author of the mainline bcm283x-rpi-usb-otg.dtsi i was trying to > optimize the fifo sizes for EP 6 and 7. But i don't remember why. So my > suggestion for a fix would be: > > g-tx-fifo-size = <256 256 256 512 512 768 768>; > > But i'm also unsure about the values. > IIUC this code https://github.com/torvalds/linux/blob/master/drivers/usb/dwc2/gadget.c#L4091 optimizes the FIFO assignment to endpoints. From that I would conclude that correct values are specific for each use-case configuration of endpoints. Maybe a varied selection (256, 512, 768) is more convenient than just 256 and 512. I really do not know what use cases need what TX fifo values. BTW perhaps this comment https://github.com/torvalds/linux/blob/master/drivers/usb/dwc2/gadget.c#L327 is a bit misleading since that code does not do the assignment, just stores the size distribution to the DPTXFSIZN register, IIUC. Best regards, Pavel.
