[PATCH v3 00/11] serial: sh-sci: Hardware Flow Control Updates

From: Geert Uytterhoeven
Date: Fri Jun 03 2016 - 06:03:46 EST

Hi Greg, Jiri, Peter,

This patch series contains updates to the Renesas SCI UART driver,
related to hardware flow control:
- Patches 1-2: Device Tree binding updates for GPIO-controlled modem
lines, and for dedicated RTS/CTS modem lines,
- Patches 3-4: Driver support for GPIO-controlled modem lines, using
the serial_mctrl_gpio helpers,
- New patches 5-11: Driver support for hardware-assisted (automatic)
hardware flow control, using the dedicated RTS/CTS modem lines.

Changes compared to v2:
- No code changes,
- Add Acked-by, Reviewed-by.

Changes compared to v1 (more details in the individual patches):
- Add Acked-by,
- Refer to the Generic Serial DT Bindings,
- Drop out[12]-gpios,
- Reject combining GPIO and dedicated RTS/CTS,
- Drop "serial: sh-sci: Replace SCIx_HAVE_RTSCTS by standard
- Add support for hardware-assisted automatic RTS/CTS control on

- The patches apply to v4.7-rc1 and next-20160603.

This was tested on r8a7791/koelsch and r8a7740/armadillo, using UARTs
and GPIO pins on expansion connectors.

Expected behavior, using GPIO-based RTS/CTS as a reference:
- When CRTSCTS is disabled:
- Reading from a UART asserts the RTS line,
- Writing to a UART asserts the RTS line.
- When CRTSCTS is enabled:
- Reading from a UART asserts the RTS line,
- Writing to a UART asserts the RTS line.
- Writing is blocked until CTS is asserted.

Hardware-assisted hardware flow control with HSCIF and SCIFB on
r8a7791/koelsch behaves as expected when dedicated RTS/CTS modem lines
are enabled (beware the large transmission FIFOs on SCIFB ;-)

For SCIFA on r8a7740/armadillo, manually overriding (asserting) the RTS
signal doesn't seem to work. Hence when CRTSCTS is disabled, RTS is
never asserted. When CRTSCTS is enabled, hardware-assisted RTS/CTS does
control RTS as expected. As SCIFA on r8a7791 doesn't have dedicated
RTS/CTS modem lines, I cannot compare.

DT overlays for testing can be found in the topic/renesas-overlays
branch of

Regression testing on platforms without DT and/or GPIOLIB support
(SuperH) would be appreciated.
Compile-tested on ecovec24_defconfig(GPIOLIB=y) and se7780_defconfig

Please apply, thanks!

Geert Uytterhoeven (11):
serial: sh-sci: Update DT binding documentation for GPIO modem lines
serial: sh-sci: Update DT binding documentation for dedicated RTS/CTS
serial: sh-sci: Always set TIOCM_CTS in .get_mctrl() callback
serial: sh-sci: Add support for GPIO-controlled modem lines
serial: sh-sci: Do not open-code sci_getreg()
serial: sh-sci: Add more Serial Port Register documentation
serial: sh-sci: Add more Serial Port Control/Data Register
serial: sh-sci: Correct pin initialization on (H)SCIF
serial: sh-sci: Add pin initialization for SCIFA/SCIFB
serial: sh-sci: Fix support for hardware-assisted RTS/CTS
serial: sh-sci: Add DT support for dedicated RTS/CTS

.../bindings/serial/renesas,sci-serial.txt | 4 +
drivers/tty/serial/Kconfig | 1 +
drivers/tty/serial/sh-sci.c | 177 ++++++++++++++++++---
drivers/tty/serial/sh-sci.h | 24 ++-
4 files changed, 173 insertions(+), 33 deletions(-)




Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds