tty: serial: sh-sci: Hide DMA config question

This change “tty: serial: sh-sci: Hide DMA config question” in Linux kernel is authored by Geert Uytterhoeven <geert+renesas [at]> on Thu Nov 30 14:12:01 2017 +0100.

tty: serial: sh-sci: Hide DMA config question

On most Renesas ARM platforms, the SCIF serial ports can be used with
DMA, so most users will want DMA support to be enabled.

On SuperH platforms, SCI(F) serial ports cannot be used with DMA yet
(see also commit 219fb0c1436e4893 ("serial: sh-sci: Remove the platform
data dma slave rx/tx channel IDs")), so users will want it disabled to
reduce kernel size.

Hence follow the above rationale to configure the default, unless
CONFIG_EXPERT is enabled.

Signed-off-by: Geert Uytterhoeven <>
Signed-off-by: Greg Kroah-Hartman <>

This Linux change may have been applied to various maintained Linux releases and you can find Linux releases including commit be7e251.

There are 3 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 drivers/tty/serial/Kconfig | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 952a2c6..4e6dfb0 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -781,8 +781,9 @@ config SERIAL_SH_SCI_EARLYCON
 	default ARCH_RENESAS || H8300
-	bool "DMA support"
+	bool "DMA support" if EXPERT
 	depends on SERIAL_SH_SCI && DMA_ENGINE
+	default ARCH_RENESAS
 	bool "Enable PNX8XXX SoCs' UART Support"

The commit for this change in Linux stable tree is be7e251 (patch).

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