• S
    usb: chipidea: Add errata for revision 2.40a · 06bdfcdb
    Sanchayan Maity 提交于
    At chipidea revision 2.40a, there is a below errata:
    
    9000531823  B2-Medium  Adding a dTD to a Primed Endpoint May Not Get Recognized
    
    Title: Adding a dTD to a Primed Endpoint May Not Get Recognized
    
    Impacted Configuration: All device mode configurations.
    
    Description:
    There is an issue with the add dTD tripwire semaphore (ATDTW bit in USBCMD register)
    that can cause the controller to ignore a dTD that is added to a primed endpoint.
    When this happens, the software can read the tripwire bit and the status bit at '1'
    even though the endpoint is unprimed.
    
    After executing a dTD, the device controller endpoint state machine executes a final
    read of the dTD terminate bit to check if the application added a dTD to the linked
    list at the last moment. This read is done in the finpkt_read_latest_next_td (44) state.
    After the read is performed, if the terminate bit is still set, the state machine moves
    to unprime the endpoint. The decision to unprime the endpoint is done in the
    checkqh_decision (59) state, based on the value of the terminate bit.
    Before reaching the checkqh_decision state, the state machine traverses the
    writeqhtd_status (57), writeqh_status (56), and release_prime_mask (42) states.
    As shown in the waveform, the ep_addtd_tripwire_clr signal is not set to clear
    the tripwire bit in these states.
    
    Workaround:
    The software must implement a periodic poll cycle, and check for each dTD
    pending on execution (Active = 1), if the enpoint is primed. It can do this by reading
    the corresponding bits in the ENDPTPRIME and ENDPTSTAT registers. If these bits are
    read at 0, the software needs to re-prime the endpoint by writing 1 to the corresponding
    bit in the ENDPTPRIME register. This can be done for every microframe, every frame or
    with a larger interval, depending on the urgency of transfer execution for the application.
    Tested-by: NStefan Agner <stefan@agner.ch>
    Signed-off-by: NPeter Chen <peter.chen@freescale.com>
    Signed-off-by: NSanchayan Maity <maitysanchayan@gmail.com>
    Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    06bdfcdb
udc.c 45.8 KB