linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
* [PATCH v2 1/9] serial: uapi: add SER_RS485_DELAY_IN_USEC flag to struct serial_rs485
@ 2019-02-21 17:17 Martin Kepplinger
  2019-02-21 17:17 ` [PATCH v2 2/9] Documentation: serial-rs485: document SER_RS485_DELAY_IN_USEC flag Martin Kepplinger
                   ` (8 more replies)
  0 siblings, 9 replies; 12+ messages in thread
From: Martin Kepplinger @ 2019-02-21 17:17 UTC (permalink / raw)
  To: gregkh, robh+dt, mark.rutland, jslaby, corbet, richard.genoud,
	nicolas.ferre, alexandre.belloni, ludovic.desroches,
	mcoquelin.stm32, alexandre.torgue, linux-serial, devicetree,
	linux-arm-kernel, linux-stm32
  Cc: linux-kernel, Martin Kepplinger

[-- Attachment #1: Type: text/plain, Size: 2659 bytes --]

This extends the user interface for rs485 communication:

We add a new flag, SER_RS485_DELAY_IN_USEC, to struct serial_rs485 that
indicates that delay_rts_before_send and delay_rts_after_send values are
interpreted in microsecond units.

Up until now, the code comment defined these values to hold the delays in
millisecond units. Especially with fast data rates (1Mbaut or more) that
are not too uncommon for RS485, 1ms become quite long. Users need to be
able to set shorter delays than 1 ms in order not to slow down the channel
unnecessarily.

So when delays are needed, but not as long as 1ms, this enables faster
communication channels without changing the baudrate.

Signed-off-by: Martin Kepplinger <martin.kepplinger@ginzinger.com>
---

revision history
----------------
v2: re-send as a proper series after fixing my mailserver
v1: initial implementation idea


So have this totally quirky patch that uses udelay() in our tree
for a looong time now because of the above reasons - and because we are lazy.
This is an attempt to get rid of said patch on our side and fix this properly.

What do you thing about adding a flag in general?

The following patches should integrate this idea in devicetree and drivers.
These changes are NOT tested on hardware but should behave predictably
enough. I use the delays in a driver that doesn't implement them yet at
all. I'll do that after this (or something similar) is merged - it's a 2-liner
then.

Also, a patch to the rs485conf tool, that is sometimes used instead of
ioctl() directly, will be prepared as well.

thanks

                                 martin



 include/uapi/linux/serial.h | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/serial.h b/include/uapi/linux/serial.h
index 93eb3c496ff1..c16c950ebca2 100644
--- a/include/uapi/linux/serial.h
+++ b/include/uapi/linux/serial.h
@@ -126,8 +126,15 @@ struct serial_rs485 {
 #define SER_RS485_TERMINATE_BUS		(1 << 5)	/* Enable bus
 							   termination
 							   (if supported) */
-	__u32	delay_rts_before_send;	/* Delay before send (milliseconds) */
-	__u32	delay_rts_after_send;	/* Delay after send (milliseconds) */
+#define SER_RS485_DELAY_IN_USEC		(1 << 6)	/* delay_rts_*_send
+							   values are given in
+							   microseconds */
+	__u32	delay_rts_before_send;	/* Delay before send (milliseconds
+					   by default. microseconds if flag
+					   is set) */
+	__u32	delay_rts_after_send;	/* Delay after send (milliseconds
+					   by default. microseconds if flag
+					   is set) */
 	__u32	padding[5];		/* Memory is cheap, new structs
 					   are a royal PITA .. */
 };
-- 
2.20.1


[-- Attachment #2: smime.p7s --]
[-- Type: application/x-pkcs7-signature, Size: 3616 bytes --]

^ permalink raw reply related	[flat|nested] 12+ messages in thread
end of thread, other threads:[~2019-03-29 14:36 UTC | newest]

Thread overview: 12+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-02-21 17:17 [PATCH v2 1/9] serial: uapi: add SER_RS485_DELAY_IN_USEC flag to struct serial_rs485 Martin Kepplinger
2019-02-21 17:17 ` [PATCH v2 2/9] Documentation: serial-rs485: document SER_RS485_DELAY_IN_USEC flag Martin Kepplinger
2019-02-21 17:17 ` [PATCH v2 3/9] serial: core: add rs485-rts-delay-us devicetree property for RS485 Martin Kepplinger
2019-02-22 23:44   ` Rob Herring
2019-02-21 17:17 ` [PATCH v2 4/9] serial: 8250: add support for rs485 RTS delays in microseconds Martin Kepplinger
2019-03-29 14:36   ` Ahmad Fatoum
2019-02-21 17:17 ` [PATCH v2 5/9] serial: omap-serial: " Martin Kepplinger
2019-02-21 17:17 ` [PATCH v2 6/9] serial: sc16is7xx: " Martin Kepplinger
2019-02-21 17:17 ` [PATCH v2 7/9] serial: atmel_serial: set SER_RS485_DELAY_IN_USEC accordingly Martin Kepplinger
2019-02-21 17:17 ` [PATCH v2 8/9] serial: fsl_lpuart: " Martin Kepplinger
2019-02-21 17:17 ` [PATCH v2 9/9] serial: st32-usart: " Martin Kepplinger
2019-03-08  7:36 ` [PATCH v2 1/9] serial: uapi: add SER_RS485_DELAY_IN_USEC flag to struct serial_rs485 Martin Kepplinger

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).