Treat each completed full size write to /dev/ttyDBC0 as a separate usb transfer. Make sure the size of the TRBs matches the size of the tty write by first queuing as many max packet size TRBs as possible up to the last TRB which will be cut short to match the size of the tty write.

This solves an issue where userspace writes several transfers back to back via /dev/ttyDBC0 into a kfifo before dbgtty can find available request to turn that kfifo data into TRBs on the transfer ring.

The boundary between transfer was lost as xhci-dbgtty then turned everyting in the kfifo into as many 'max packet size' TRBs as possible.

DbC would then send more data to the host than intended for that transfer, causing host to issue a babble error.

Refuse to write more data to kfifo until previous tty write data is turned into properly sized TRBs with data size boundaries matching tty write size

Tested-by: Uday M Bhat uday.m.bhat@intel.com Tested-by: Łukasz Bartosik ukaszb@chromium.org Cc: stable@vger.kernel.org Signed-off-by: Mathias Nyman mathias.nyman@linux.intel.com --- drivers/usb/host/xhci-dbgcap.h | 1 + drivers/usb/host/xhci-dbgtty.c | 55 ++++++++++++++++++++++++++++++---- 2 files changed, 51 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/host/xhci-dbgcap.h b/drivers/usb/host/xhci-dbgcap.h index 8ec813b6e9fd..9dc8f4d8077c 100644 --- a/drivers/usb/host/xhci-dbgcap.h +++ b/drivers/usb/host/xhci-dbgcap.h @@ -110,6 +110,7 @@ struct dbc_port { struct tasklet_struct push;

struct list_head write_pool; + unsigned int tx_boundary;

bool registered; }; diff --git a/drivers/usb/host/xhci-dbgtty.c b/drivers/usb/host/xhci-dbgtty.c index b8e78867e25a..d719c16ea30b 100644 --- a/drivers/usb/host/xhci-dbgtty.c +++ b/drivers/usb/host/xhci-dbgtty.c @@ -24,6 +24,29 @@ static inline struct dbc_port *dbc_to_port(struct xhci_dbc *dbc) return dbc->priv; }

+static unsigned int +dbc_kfifo_to_req(struct dbc_port *port, char *packet) +{ + unsigned int len; + + len = kfifo_len(&port->port.xmit_fifo); + + if (len == 0) + return 0; + + len = min(len, DBC_MAX_PACKET); + + if (port->tx_boundary) + len = min(port->tx_boundary, len); + + len = kfifo_out(&port->port.xmit_fifo, packet, len); + + if (port->tx_boundary) + port->tx_boundary -= len; + + return len; +} + static int dbc_start_tx(struct dbc_port *port) __releases(&port->port_lock) __acquires(&port->port_lock) @@ -36,7 +59,7 @@ static int dbc_start_tx(struct dbc_port *port)

while (!list_empty(pool)) { req = list_entry(pool->next, struct dbc_request, list_pool); - len = kfifo_out(&port->port.xmit_fifo, req->buf, DBC_MAX_PACKET); + len = dbc_kfifo_to_req(port, req->buf); if (len == 0) break; do_tty_wake = true; @@ -200,14 +223,32 @@ static ssize_t dbc_tty_write(struct tty_struct *tty, const u8 *buf, { struct dbc_port *port = tty->driver_data; unsigned long flags; + unsigned int written = 0;

spin_lock_irqsave(&port->port_lock, flags); - if (count) - count = kfifo_in(&port->port.xmit_fifo, buf, count); - dbc_start_tx(port); + + /* + * Treat tty write as one usb transfer. Make sure the writes are turned + * into TRB request having the same size boundaries as the tty writes. + * Don't add data to kfifo before previous write is turned into TRBs + */ + if (port->tx_boundary) { + spin_unlock_irqrestore(&port->port_lock, flags); + return 0; + } + + if (count) { + written = kfifo_in(&port->port.xmit_fifo, buf, count); + + if (written == count) + port->tx_boundary = kfifo_len(&port->port.xmit_fifo); + + dbc_start_tx(port); + } + spin_unlock_irqrestore(&port->port_lock, flags);

- return count; + return written; }

static int dbc_tty_put_char(struct tty_struct *tty, u8 ch) @@ -241,6 +282,10 @@ static unsigned int dbc_tty_write_room(struct tty_struct *tty)

spin_lock_irqsave(&port->port_lock, flags); room = kfifo_avail(&port->port.xmit_fifo); + + if (port->tx_boundary) + room = 0; + spin_unlock_irqrestore(&port->port_lock, flags);

return room;