Hi，all：
我们产品A使用I.MX6DL（MCIMX6U7CVM08AC）和 2片MT41K256M16TW-107来组成32位的DDR3系统。在调试之初，我按照 https://community.nxp.com/docs/DOC-94917 文档，做了DDR3基本配置、校准和压力测试。
所有项都通过了，系统在正常运行时也没有异常。
硬件设计原理图如下：
当我将U盘插入板子时，我发现在"/dev/"目录下比没有产生类似 "sd*" 的设备节点，内核输出信息如下：
usb 2-1.2: new high-speed USB device number 6 using ci_hdrc usb 2-1.2: New USB device found, idVendor=0781, idProduct=556b usb 2-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3 usb 2-1.2: Product: Cruzer Edge usb 2-1.2: Manufacturer: SanDisk usb 2-1.2: SerialNumber: 4C530399950108110182 usb-storage 2-1.2:1.0: USB Mass Storage device detected scsi host3: usb-storage 2-1.2:1.0 scsi 3:0:0:0: scsi scan: INQUIRY result too short (5), using 36 scsi 3:0:0:0: Direct-Access PQ: 0 ANSI: 0 usb 2-1.2: USB disconnect, device number 6 sd 3:0:0:0: [sda] Read Capacity(10) failed: Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK sd 3:0:0:0: [sda] Sense not available. sd 3:0:0:0: [sda] Write Protect is off sd 3:0:0:0: [sda] Mode Sense: 55 53 42 53 sd 3:0:0:0: [sda] Incomplete mode parameter data sd 3:0:0:0: [sda] Assuming drive cache: write through sd 3:0:0:0: [sda] Read Capacity(10) failed: Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK sd 3:0:0:0: [sda] Sense not available. sd 3:0:0:0: [sda] Attached SCSI disk |
我们硬件工程师测试了DDR3相关的电源，发现没有异常（整个DDR3相关电源由MMPF0100F0AEP PMIC芯片提供）。
我在u-boot下使用usb命令是可以正常读取U盘中文件的内容的；并且在Linux下，我也用USB接口的WIFI网卡试过，可以进行网络通信，USB通信看起来也没有问题。
然后，我使用tcpdump和wireshark抓取USB发送的URB包，发现在 int usb_stor_Bulk_transport(struct scsi_cmnd *srb, struct us_data *us) 函数中发出的SCSI命令是错误的，而这发生在内存拷贝上。
为了修改这个问题我添加了以下修改内容
/** * CONFIG_USB_MEMORY_DATA_INCOHERENT_FIXED * * memset(bcb->CDB, 0, sizeof(bcb->CDB)); * memcpy(bcb->CDB, srb->cmnd, bcb->Length); * Does not work, data can not copy from srb->cmnd to bcb->CDB * I just use one temperary memory to avoid memory copy form srb->cmnd to bcb->CDB dirctly. * Wow!, it does work!! * Fix this problem, if find real reason */ int usb_stor_Bulk_transport(struct scsi_cmnd *srb, struct us_data *us) { struct bulk_cb_wrap *bcb = (struct bulk_cb_wrap *) us->iobuf; struct bulk_cs_wrap *bcs = (struct bulk_cs_wrap *) us->iobuf; unsigned int transfer_length = scsi_bufflen(srb); unsigned int residue; int result; int fake_sense = 0; unsigned int cswlen; unsigned int cbwlen = US_BULK_CB_WRAP_LEN; #ifdef CONFIG_USB_MEMORY_DATA_INCOHERENT_FIXED __u8 cdb[64], *tmp; #endif /* Take care of BULK32 devices; set extra byte to 0 */ if (unlikely(us->fflags & US_FL_BULK32)) { cbwlen = 32; us->iobuf[31] = 0; } /* set up the command wrapper */ bcb->Signature = cpu_to_le32(US_BULK_CB_SIGN); bcb->DataTransferLength = cpu_to_le32(transfer_length); bcb->Flags = srb->sc_data_direction == DMA_FROM_DEVICE ? US_BULK_FLAG_IN : 0; bcb->Tag = ++us->tag; bcb->Lun = srb->device->lun; if (us->fflags & US_FL_SCM_MULT_TARG) bcb->Lun |= srb->device->id << 4; bcb->Length = srb->cmd_len; /* copy the command payload */ #ifdef CONFIG_USB_MEMORY_DATA_INCOHERENT_FIXED memset(cdb, 0, sizeof(cdb)); memcpy(&cdb[1], srb->cmnd, srb->cmd_len); cdb[0] = srb->cmd_len; /* bcb->Length = srb->cmd_len */ tmp = &(bcb->Length); memcpy(tmp, cdb, srb->cmd_len + 1); /* bcb->Length + CDB */ #else memset(bcb->CDB, 0, sizeof(bcb->CDB)); memcpy(bcb->CDB, srb->cmnd, bcb->Length); #endif /* send it to out endpoint */ usb_stor_dbg(us, "Bulk Command S 0x%x T 0x%x L %d F %d Trg %d LUN %d CL %d\n", le32_to_cpu(bcb->Signature), bcb->Tag, le32_to_cpu(bcb->DataTransferLength), bcb->Flags, (bcb->Lun >> 4), (bcb->Lun & 0x0F), bcb->Length); result = usb_stor_bulk_transfer_buf(us, us->send_bulk_pipe, bcb, cbwlen, NULL); usb_stor_dbg(us, "Bulk command transfer result=%d\n", result); if (result != USB_STOR_XFER_GOOD) return USB_STOR_TRANSPORT_ERROR; /* DATA STAGE */ /* send/receive data payload, if there is any */ /* Some USB-IDE converter chips need a 100us delay between the * command phase and the data phase. Some devices need a little * more than that, probably because of clock rate inaccuracies. */ if (unlikely(us->fflags & US_FL_GO_SLOW)) udelay(125); if (transfer_length) { unsigned int pipe = srb->sc_data_direction == DMA_FROM_DEVICE ? us->recv_bulk_pipe : us->send_bulk_pipe; result = usb_stor_bulk_srb(us, pipe, srb); usb_stor_dbg(us, "Bulk data transfer result 0x%x\n", result); if (result == USB_STOR_XFER_ERROR) return USB_STOR_TRANSPORT_ERROR; /* If the device tried to send back more data than the * amount requested, the spec requires us to transfer * the CSW anyway. Since there's no point retrying the * the command, we'll return fake sense data indicating * Illegal Request, Invalid Field in CDB. */ if (result == USB_STOR_XFER_LONG) fake_sense = 1; /* * Sometimes a device will mistakenly skip the data phase * and go directly to the status phase without sending a * zero-length packet. If we get a 13-byte response here, * check whether it really is a CSW. */ if (result == USB_STOR_XFER_SHORT && srb->sc_data_direction == DMA_FROM_DEVICE && transfer_length - scsi_get_resid(srb) == US_BULK_CS_WRAP_LEN) { struct scatterlist *sg = NULL; unsigned int offset = 0; if (usb_stor_access_xfer_buf((unsigned char *) bcs, US_BULK_CS_WRAP_LEN, srb, &sg, &offset, FROM_XFER_BUF) == US_BULK_CS_WRAP_LEN && bcs->Signature == cpu_to_le32(US_BULK_CS_SIGN)) { usb_stor_dbg(us, "Device skipped data phase\n"); scsi_set_resid(srb, transfer_length); goto skipped_data_phase; } } } /* See flow chart on pg 15 of the Bulk Only Transport spec for * an explanation of how this code works. */ /* get CSW for device status */ usb_stor_dbg(us, "Attempting to get CSW...\n"); result = usb_stor_bulk_transfer_buf(us, us->recv_bulk_pipe, bcs, US_BULK_CS_WRAP_LEN, &cswlen); /* Some broken devices add unnecessary zero-length packets to the * end of their data transfers. Such packets show up as 0-length * CSWs. If we encounter such a thing, try to read the CSW again. */ if (result == USB_STOR_XFER_SHORT && cswlen == 0) { usb_stor_dbg(us, "Received 0-length CSW; retrying...\n"); result = usb_stor_bulk_transfer_buf(us, us->recv_bulk_pipe, bcs, US_BULK_CS_WRAP_LEN, &cswlen); } /* did the attempt to read the CSW fail? */ if (result == USB_STOR_XFER_STALLED) { /* get the status again */ usb_stor_dbg(us, "Attempting to get CSW (2nd try)...\n"); result = usb_stor_bulk_transfer_buf(us, us->recv_bulk_pipe, bcs, US_BULK_CS_WRAP_LEN, NULL); } /* if we still have a failure at this point, we're in trouble */ usb_stor_dbg(us, "Bulk status result = %d\n", result); if (result != USB_STOR_XFER_GOOD) return USB_STOR_TRANSPORT_ERROR; skipped_data_phase: /* check bulk status */ residue = le32_to_cpu(bcs->Residue); usb_stor_dbg(us, "Bulk Status S 0x%x T 0x%x R %u Stat 0x%x\n", le32_to_cpu(bcs->Signature), bcs->Tag, residue, bcs->Status); if (!(bcs->Tag == us->tag || (us->fflags & US_FL_BULK_IGNORE_TAG)) || bcs->Status > US_BULK_STAT_PHASE) { usb_stor_dbg(us, "Bulk logical error\n"); return USB_STOR_TRANSPORT_ERROR; } /* Some broken devices report odd signatures, so we do not check them * for validity against the spec. We store the first one we see, * and check subsequent transfers for validity against this signature. */ if (!us->bcs_signature) { us->bcs_signature = bcs->Signature; if (us->bcs_signature != cpu_to_le32(US_BULK_CS_SIGN)) usb_stor_dbg(us, "Learnt BCS signature 0x%08X\n", le32_to_cpu(us->bcs_signature)); } else if (bcs->Signature != us->bcs_signature) { usb_stor_dbg(us, "Signature mismatch: got %08X, expecting %08X\n", le32_to_cpu(bcs->Signature), le32_to_cpu(us->bcs_signature)); return USB_STOR_TRANSPORT_ERROR; } /* try to compute the actual residue, based on how much data * was really transferred and what the device tells us */ if (residue && !(us->fflags & US_FL_IGNORE_RESIDUE)) { /* Heuristically detect devices that generate bogus residues * by seeing what happens with INQUIRY and READ CAPACITY * commands. */ if (bcs->Status == US_BULK_STAT_OK && scsi_get_resid(srb) == 0 && ((srb->cmnd[0] == INQUIRY && transfer_length == 36) || (srb->cmnd[0] == READ_CAPACITY && transfer_length == 8))) { us->fflags |= US_FL_IGNORE_RESIDUE; } else { residue = min(residue, transfer_length); scsi_set_resid(srb, max(scsi_get_resid(srb), (int) residue)); } } /* based on the status code, we report good or bad */ switch (bcs->Status) { case US_BULK_STAT_OK: /* device babbled -- return fake sense data */ if (fake_sense) { memcpy(srb->sense_buffer, usb_stor_sense_invalidCDB, sizeof(usb_stor_sense_invalidCDB)); return USB_STOR_TRANSPORT_NO_SENSE; } /* command good -- note that data could be short */ return USB_STOR_TRANSPORT_GOOD; case US_BULK_STAT_FAIL: /* command failed */ return USB_STOR_TRANSPORT_FAILED; case US_BULK_STAT_PHASE: /* phase error -- note that a transport reset will be * invoked by the invoke_transport() function */ return USB_STOR_TRANSPORT_ERROR; } /* we should never get here, but if we do, we're in trouble */ return USB_STOR_TRANSPORT_ERROR; } |
作此修改后，可以暂时解决U盘不能识别问题。经过测试文件拷贝也正常。
现在我们开发了另一个项目B，项目B使用I.MX6Q，但由于硬件工程师设计失误，我们使用了1片MT41K256M16TW-107组成16位的DDR3，我们发现即使在内核不添加CONFIG_USB_MEMORY_DATA_INCOHERENT_FIXED相关代码时，插入U盘也能正常通信。因此我又修改了A项目的DDR3配置，将DDR3的位宽修改为16bits，同样在不添加CONFIG_USB_MEMORY_DATA_INCOHERENT_FIXED相关代码的情况下和U盘能正常通信。
因此我想问一下，I.MX6在使用32位的DDR3时是否有什么bugs？或者我在DDR3的配置上存在问题？
附件包括我们在u-boot中使用的DCD文件mx6dl_2x_mt41k256m16.cfg，mt41k256m16 数据手册
1 解答
