On Fri, Jul 12, 2013 at 03:11:46PM +0300, Felipe Balbi wrote: > hi, > > On Fri, Jul 12, 2013 at 02:55:42PM +0300, Grygorii Strashko wrote: > > Since commit a630fbf "serial: omap: Fix device tree based PM runtime" > > the OMAP serial driver will always try to restore its context in > > serial_omap_runtime_resume(). But the problem is that during driver > > initialization the UART context is not ready yet and, as result, first > > call to pm_runtime_get*() will cause UART register overwriting by all > > zeros. This causes Kernel boot hang in case if "earlyprintk" feature is > > enabled at least [1]. > > > > Unfortunately, there is no exact place in driver now where we can > > determine that UART context is ready - most of registers configured in > > serial_omap_set_termios(), but some of them in other places. > > More over, even if PM runtime will be disabled (blocked) during OMAP > > serial driver probe() execution [2],[3] it will fix only console UART, > > but context of other UARTs will be overwriting by all zeros during first > > access to the corresponding UART. > > > > To fix this issue: > > - introduce additional "initialized" flag and update PM runtime callback > > to do nothing if its not set. Set "initialized" at the end of probe(). > > - read current UART registers configuration in probe and use it by > > default. > > > > [1] http://www.spinics.net/lists/arm-kernel/msg256828.html > > [2] http://www.spinics.net/lists/arm-kernel/msg258062.html > > [3] http://www.spinics.net/lists/arm-kernel/msg258040.html > > > > CC: Tony Lindgren <tony@xxxxxxxxxxx> > > CC: Rajendra Nayak <rnayak@xxxxxx> > > CC: Felipe Balbi <balbi@xxxxxx> > > CC: Kevin Hilman <khilman@xxxxxxxxxx> > > > > Signed-off-by: Grygorii Strashko <grygorii.strashko@xxxxxx> > > --- > > tested on OMAP4 SDP with and without earlyprintk enabled. > > drivers/tty/serial/omap-serial.c | 27 ++++++++++++++++++++++++++- > > 1 file changed, 26 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c > > index f39bf0c..e1e9667 100644 > > --- a/drivers/tty/serial/omap-serial.c > > +++ b/drivers/tty/serial/omap-serial.c > > @@ -162,6 +162,7 @@ struct uart_omap_port { > > struct work_struct qos_work; > > struct pinctrl *pins; > > bool is_suspending; > > + bool initialized; > > you really think adding this sort of bool flag is the best thing we can > do ? Something which will, quite likely, spread through every single > driver ? I agree, that's not ok, please fix this up "properly" somehow. thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
