On 2017-06-14 16:38, Ulrich Hecht wrote:
> Hi!
>
> This is an attempt to add multiplexer support to serdev, specifically
> GPIO-based multiplexing.
>
> Our use case is the Renesas Blanche V2H board with several MAX9260 GMSL
> deserializers attached to one serial port. A sample driver that implements
> i2c passthrough over the GMSL link is part of this series. This device
> wants to be talked to with even parity, so a patch implementing parity
> control in serdev is included as well.
>
> The board-specific part of this series depends on the "pinctrl: sh-pfc:
> r8a7792: Add SCIF1 pin groups" patch.
>
> Please tell me if this is a suitable way to implement this functionality
> in serdev, or how to improve it. Thank you.
When I look at patch 2/4, I can't help but think that you should perhaps
consider the new mux framework available in linux-next [1]. But as the
author of that, I'm maybe biased...
You then support other means of controlling the mux automatically (i.e.
you get free support for non-gpio muxes). You also get support for
sharing the mux controller should the same gpio pins control muxes
for unrelated functions (which happened for my hw).
However, I see that you request the gpios when you select the mux, and
free them when you deselect it. That is not how the gpio mux in the
mux framework operates; it instead keeps the gpios requested and either
leaves the gpios as-is on deselect or sets a specific idle value. But
that is perhaps ok for this use-case too?
Cheers,
peda
[1] https://lkml.org/lkml/2017/5/14/160
> CU
> Uli
>
>
> Ulrich Hecht (4):
> serdev: add method to set parity
> serdev: add GPIO-based multiplexer support
> max9260: add driver for i2c over GMSL passthrough
> ARM: dts: blanche: add SCIF1 and MAX9260 deserializer
>
> arch/arm/boot/dts/r8a7792-blanche.dts | 45 ++
> drivers/media/i2c/Kconfig | 6 +
> drivers/media/i2c/Makefile| 1 +
> drivers/media/i2c/max9260.c | 294
> ++
> drivers/tty/serdev/Kconfig| 3 +
> drivers/tty/serdev/Makefile | 1 +
> drivers/tty/serdev/core.c | 55 ++-
> drivers/tty/serdev/mux-gpio.c | 80 +
> drivers/tty/serdev/serdev-ttyport.c | 17 ++
> include/linux/serdev.h| 30 +++-
> 10 files changed, 528 insertions(+), 4 deletions(-)
> create mode 100644 drivers/media/i2c/max9260.c
> create mode 100644 drivers/tty/serdev/mux-gpio.c
>
