On 5/20/19 16:56, Jorge Ramirez wrote: > On 5/20/19 16:51, Stephen Boyd wrote: >> Quoting Jorge Ramirez-Ortiz (2019-05-20 03:34:35) >>> When the tty layer requests the uart to throttle, the current code >>> executing in msm_serial will trigger "Bad mode in Error Handler" and >>> generate an invalid stack frame in pstore before rebooting (that is if >>> pstore is indeed configured: otherwise the user shall just notice a >>> reboot with no further information dumped to the console). >>> >>> This patch replaces the PIO byte accessor with the word accessor >>> already used in PIO mode. >> >> Because the hardware only accepts word based accessors and fails >> otherwise? I can believe that. >> >> I wonder if the earlier UART hardware this driver used to support (i.e. >> pre-DM) would accept byte access to the registers. It's possible, but we >> don't really care because those boards aren't supported. > > ok. > > also the PIO path uses iowrite32_rep to write a number of bytes (from 1 > to 4) so I think it is also appropriate to use it for XON/XOFF. > >> >>> >>> Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@xxxxxxxxxx> >>> --- >> >> Reviewed-by: Stephen Boyd <swboyd@xxxxxxxxxxxx> >> >>> drivers/tty/serial/msm_serial.c | 5 ++++- >>> 1 file changed, 4 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c >>> index 109096033bb1..23833ad952ba 100644 >>> --- a/drivers/tty/serial/msm_serial.c >>> +++ b/drivers/tty/serial/msm_serial.c >>> @@ -869,10 +870,12 @@ static void msm_handle_tx(struct uart_port *port) >>> else >>> tf = port->membase + UART_TF; >>> >>> + buf[0] = port->x_char; >>> + >>> if (msm_port->is_uartdm) >>> msm_reset_dm_count(port, 1); >>> >>> - iowrite8_rep(tf, &port->x_char, 1); >>> + iowrite32_rep(tf, buf, 1); >> >> I suppose it's OK to write some extra zeroes here? >> >> > > yeah, semantically confusing msm_reset_dm_count is what really matters: > it tells the hardware to only take n bytes (in this case only one) so > the others will be ignored um after I said this, maybe iowrite32_rep should only be applied to uartdm ... what do you think? > >
