On DM355 with CPPI DMA enabled, operating as gadget serial, the USB driver RX side locks up when sent a 64-byte line of text. Up to and above 64 bytes are OK, exactly 64 bytes wedges it. I see the 64-byte line come out of "cat /dev/ttyGS0", but then nothing after. The TX side still works OK, but if the other end tries to send any more, it times out. If it helps at all, a few times when testing this I have seen extra 1-byte transfers appear at the g_serial layer rather than wedging when a 64-byte packet was sent. I haven't been able to reproduce this reliably. But that is to say I was seeing: Send 64 bytes, g_serial layer gets 64-byte transfer followed by a 1-byte transfer containing garbage: always the first character of some previous line received. Send any other line size e.g. 63 bytes, g_serial layer gets a single 63-byte transfer. Disabling DMA fixes the problem, but I'd like to have DMA if possible, and help fix this. I observed this problem in a 2.6.34 based kernel, I am now running the master of git://git.kernel.org/pub/scm/linux/kernel/git/khilman/linux-davinci.git with local board support etc. patches applied, and tried applying the 12 musb fix patches at the top of http://gitorious.org/usb/usb/commits/musb which did not help. loading musb_hdrc with debug=7 shows up some suspicious differences when receiving a 64-byte line, some console logs below. I note that bits 0x3 of csr are set in the problem case. 63-byte RX (ok): cppi_interrupt 1172: CPPI IRQ Tx0 Rx1 cppi_dump_rx 377: RX DMA0/K: 0 left, csr 2000, 00000000 H00000000 S873388c0 C873388c0, B86ec6c3f L003f01c1 0000003f .. 873388c0 cppi_rx_scan 1045: C/RXBD 873388c0: nxt 00000000 buf 86ec6c00 off.len 0000003f opt.len d000003f (0) cppi_dump_rx 377: RX DMA0/completed: 0 left, csr 2000, 00000000 H00000000 S873388c0 C873388c0, B86ec6c3f L003f01c1 0000003f .. 873388c0 musb_g_rx 757: <== ep1out, rxcsr 2000 (dma) c6e92dc0 musb_g_rx 800: RXCSR1 0000, dma off, 0000, len 63, req c6e92dc0 musb_g_giveback 143: ep1out done request c6e92dc0, 63/512 gs_read_complete: req c6e92dc0 cppi_next_rx_segment 831: RX DMA0 seg, maxp 512 onepacket bds 1 (cnt 0) dma 0x86854000 len 512 0/512 RXBD/S 873388a0: nxt 00000000 buf 86854000 off.blen 00000200 opt.plen e0000200 cppi_dump_rx 377: RX DMA0/S: 3 left, csr 0000, 00000000 H873388a0 S873388c0 C873388c0, B86ec6c3f L003f01c1 0000003f .. 873388c0 davinci_interrupt 292: IRQ 00000000 ttyGS 63 bytes to tty (s S . ... 0x39 0x0a) musb_gadget_queue 1120: <== to ep1out request=c6e92dc0 musb_gadget_queue 1120: <== to ep1in request=c6e927c0 musb_ep_restart 1088: <== TX/IN request c6e927c0 len 1 on hw_ep1 txstate 298: hw_ep1, maxpacket 512, fifo count 1, txcsr 2404 cppi_next_tx_segment 604: TX DMA0, pktSz 512 transparent bds 1 dma 0x86854a00 len 1 cppi_next_tx_segment 658: TXBD ff32a800: nxt 00000000 buf 86854a00 len 0001 opt e0000001 cppi_dump_tx 405: TX DMA0/S: csr 3403, H00000000 S86e71800 C86e71800 86854a01, F00020000 L00000001 .. 86e71800 txstate 410: ep1in TX/IN dma len 0/1, txcsr 3404, fifo 1/512 cppi_interrupt 1172: CPPI IRQ Tx1 Rx0 cppi_dump_tx 405: TX DMA0/E: csr 3404, H00000000 S86e71800 C86e71800 86854a01, F00020000 L00000001 .. 86e71800 cppi_interrupt 1217: C/TXBD ff32a800 n 0 b 86854a00 off 1 opt d0000000 musb_g_tx 430: <== ep1in, txcsr 3404 musb_g_tx 475: TXCSR1 2400, DMA off, len 1, req c6e927c0 musb_g_giveback 143: ep1in done request c6e927c0, 1/1 musb_g_tx 522: ep1in idle now 64-byte RX (wedges things, but gets to tty): cppi_interrupt 1172: CPPI IRQ Tx0 Rx1 cppi_dump_rx 377: RX DMA0/K: 0 left, csr 2003, 00000000 H00000000 S873388a0 C873388a0, B86854040 L004001c0 00000040 .. 873388a0 cppi_rx_scan 1045: C/RXBD 873388a0: nxt 00000000 buf 86854000 off.len 00000040 opt.len d0000040 (0) cppi_dump_rx 377: RX DMA0/completed: 0 left, csr 2003, 00000000 H00000000 S873388a0 C873388a0, B86854040 L004001c0 00000040 .. 873388a0 musb_g_rx 757: <== ep1out, rxcsr 2003 (dma) c6e92d00 musb_g_rx 800: RXCSR1 0003, dma off, 0003, len 64, req c6e92d00 musb_g_giveback 143: ep1out done request c6e92d00, 64/512 gs_read_complete: req c6e92d00 cppi_next_rx_segment 831: RX DMA0 seg, maxp 512 onepacket bds 1 (cnt 0) dma 0x86854200 len 512 0/512 RXBD/S 873388c0: nxt 00000000 buf 86854200 off.blen 00000200 opt.plen e0000200 cppi_dump_rx 377: RX DMA0/S: 3 left, csr 0003, 00000000 H873388c0 S873388a0 C873388a0, B86854040 L004001c0 00000040 .. 873388a0 davinci_interrupt 292: IRQ 00000000 ttyGS 64 bytes to tty (t T . ... 0x30 0x0a) musb_gadget_queue 1120: <== to ep1out request=c6e92d00 musb_gadget_queue 1120: <== to ep1in request=c6e927c0 musb_ep_restart 1088: <== TX/IN request c6e927c0 len 1 on hw_ep1 txstate 298: hw_ep1, maxpacket 512, fifo count 1, txcsr 2404 cppi_next_tx_segment 604: TX DMA0, pktSz 512 transparent bds 1 dma 0x86854a00 len 1 cppi_next_tx_segment 658: TXBD ff32a800: nxt 00000000 buf 86854a00 len 0001 opt e0000001 cppi_dump_tx 405: TX DMA0/S: csr 3403, H00000000 S86e71800 C86e71800 86854a01, F00020000 L00000001 .. 86e71800 txstate 410: ep1in TX/IN dma len 0/1, txcsr 3404, fifo 1/512 cppi_interrupt 1172: CPPI IRQ Tx1 Rx0 cppi_dump_tx 405: TX DMA0/E: csr 3404, H00000000 S86e71800 C86e71800 86854a01, F00020000 L00000001 .. 86e71800 cppi_interrupt 1217: C/TXBD ff32a800 n 0 b 86854a00 off 1 opt d0000000 musb_g_tx 430: <== ep1in, txcsr 3404 musb_g_tx 475: TXCSR1 2400, DMA off, len 1, req c6e927c0 musb_g_giveback 143: ep1in done request c6e927c0, 1/1 musb_g_tx 522: ep1in idle now Subsequent 63-byte RX (fails to arrive at tty) Not quite sure what's going on here, something very different: davinci_interrupt 292: IRQ 00000001 musb_interrupt 1583: ** IRQ peripheral usb0000 tx0001 rx0000 musb_g_ep0_irq 671: csr 0001, count 8, myaddr 3, ep0stage idle musb_read_fifo 283: RX ep0 fifo fec64420 count 8 buf c0363e36 musb_read_setup 605: SETUP req21.22 v0000 i0000 l0 musb_g_ep0_irq 853: handled 0, csr 0001, ep0stage wait g_serial gadget: acm ttyGS0 req21.22 v0000 i0000 l0 musb_g_ep0_queue 959: queue to ep0 (OUT/RX), length=0 musb_g_giveback 143: ep0 done request c6eca040, 0/0 -- Jon Povey jon.povey@xxxxxxxxxxxxxxx Racelogic is a limited company registered in England. 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