]> git.karo-electronics.de Git - karo-tx-linux.git/commit
serial: imx: clean up imx_poll_get_char()
authorDirk Behme <dirk.behme@de.bosch.com>
Wed, 3 Sep 2014 11:33:53 +0000 (12:33 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Mon, 8 Sep 2014 23:26:07 +0000 (16:26 -0700)
commit26c474128b96d277234f35a7fd870ed12bef96ca
treecff98901f80c6fc6d7e3e2050156893db04c5535
parentc993257bf7571945201205491de86268437ea174
serial: imx: clean up imx_poll_get_char()

Looking at the get_poll_char() function of the 8250.c serial driver,
we learn:

* poll_get_char() doesn't have to save/disable/restore the interrupt
  registers. No interrupt handling is needed in this function at all.
  Remove it.

* Don't block in case there is no data available. So instead blocking
  in the do {} while loop, just return with NO_POLL_CHAR, immediately .

Additionally, while the i.MX6 register URXD[7-0] contain the RX_DATA,
the upper bits of this register (URXD[15-10]) might contain some
control flags. To ensure that these are not returned with the data
read, just mask out URXD[7-0].

These changes fix the 'hang' working with kdb:

$ echo ttymxc3 > /sys/module/kgdboc/parameters/kgdboc
$ echo g >/proc/sysrq-trigger
[0]kdb> help
...
<hang>

Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: linux-serial@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/tty/serial/imx.c