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
