3.8.1 Handling Babble Conditions DWC_otg handles two cases of babble: packet babble and port babble. Packet babble occurs if the device sends more data than the maximum packet size for the channel. Port babble occurs if the controller continues to receive data from the device at EOF2 (the end of frame 2, which is very close to SOF). When DWC_otg detects a packet babble, it stops writing data into the Rx buffer and waits for the end of packet (EOP). When it detects an EOP, it flushes already-written data in the Rx buffer and generates a Babble interrupt to the application |
At 2025-03-11 16:41:11, "Xin Dai" <daixin_tkzc@xxxxxxx> wrote:
>When the DWC2 controller detects a packet Babble Error, where a device >transmits more data over USB than the host controller anticipates for a >transaction. It follows this process: > >1. The interrupt handler marks the transfer result of the URB as > `OVERFLOW` and returns it to the USB storage driver. >2. The USB storage driver interprets the data phase transfer result of > the BOT (Bulk-Only Transport) as `USB_STOR_XFER_LONG`. >3. The USB storage driver initiates the CSW (Command Status Wrapper) > phase of the BOT, requests an IN transaction, and retrieves the > execution status of the corresponding CBW (Command Block Wrapper) > command. >4. The USB storage driver evaluates the CSW and finds it does not meet > expectations. It marks the entire BOT transfer result as > `USB_STOR_XFER_ERROR` and notifies the SCSI layer that a `DID_ERROR` > has occurred during the transfer. >5. The USB storage driver requests the DWC2 controller to initiate a > port reset, notifying the device of an issue with the previous > transmission. >6. The SCSI layer implements a retransmission mechanism. > >In step 3, the device remains unaware of the Babble Error until the >connected port is reset. We observed that the device continues to send >512 bytes of data to the host (according to the BBB Transport protocol, >it should send only 13 bytes). However, the USB storage driver >pre-allocates a default buffer size of 64 bytes for CBW/CSW, posing a >risk of memory overflow. To mitigate this risk, we have adjusted the >buffer size to 512 bytes to prevent potential errors. > >Signed-off-by: Xin Dai <daixin_tkzc@xxxxxxx> >--- > drivers/usb/storage/usb.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > >diff --git a/drivers/usb/storage/usb.h b/drivers/usb/storage/usb.h >index 97c6196d639b..fd8dcb21137a 100644 >--- a/drivers/usb/storage/usb.h >+++ b/drivers/usb/storage/usb.h >@@ -71,7 +71,7 @@ struct us_unusual_dev { > * size we'll allocate. > */ > >-#define US_IOBUF_SIZE 64 /* Size of the DMA-mapped I/O buffer */ >+#define US_IOBUF_SIZE 512 /* Size of the DMA-mapped I/O buffer */ > #define US_SENSE_SIZE 18 /* Size of the autosense data buffer */ > > typedef int (*trans_cmnd)(struct scsi_cmnd *, struct us_data*); >-- >2.34.1
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