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    Subject[PATCH 5.10 107/575] mwifiex: Read a PCI register after writing the TX ring write pointer
    Date
    From: Jonas Dreßler <verdre@v0yd.nl>

    commit e5f4eb8223aa740237cd463246a7debcddf4eda1 upstream.

    On the 88W8897 PCIe+USB card the firmware randomly crashes after setting
    the TX ring write pointer. The issue is present in the latest firmware
    version 15.68.19.p21 of the PCIe+USB card.

    Those firmware crashes can be worked around by reading any PCI register
    of the card after setting that register, so read the PCI_VENDOR_ID
    register here. The reason this works is probably because we keep the bus
    from entering an ASPM state for a bit longer, because that's what causes
    the cards firmware to crash.

    This fixes a bug where during RX/TX traffic and with ASPM L1 substates
    enabled (the specific substates where the issue happens appear to be
    platform dependent), the firmware crashes and eventually a command
    timeout appears in the logs.

    BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=109681
    Cc: stable@vger.kernel.org
    Signed-off-by: Jonas Dreßler <verdre@v0yd.nl>
    Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
    Link: https://lore.kernel.org/r/20211011133224.15561-2-verdre@v0yd.nl
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/net/wireless/marvell/mwifiex/pcie.c | 8 ++++++++
    1 file changed, 8 insertions(+)

    --- a/drivers/net/wireless/marvell/mwifiex/pcie.c
    +++ b/drivers/net/wireless/marvell/mwifiex/pcie.c
    @@ -1480,6 +1480,14 @@ mwifiex_pcie_send_data(struct mwifiex_ad
    ret = -1;
    goto done_unmap;
    }
    +
    + /* The firmware (latest version 15.68.19.p21) of the 88W8897 PCIe+USB card
    + * seems to crash randomly after setting the TX ring write pointer when
    + * ASPM powersaving is enabled. A workaround seems to be keeping the bus
    + * busy by reading a random register afterwards.
    + */
    + mwifiex_read_reg(adapter, PCI_VENDOR_ID, &rx_val);
    +
    if ((mwifiex_pcie_txbd_not_full(card)) &&
    tx_param->next_pkt_len) {
    /* have more packets and TxBD still can hold more */

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