APPLIED: Re: [SRU OEM-B][PATCH 00/10] Support Intel Atom (Baytrail-I) HS-UART serdev slaves over tty

[Timo Aaltonen]

On 07.05.2018 13:56, Shrirang Bagul wrote:
> BugLink: http://bugs.launchpad.net/bugs/1769610
> 
> On systems using Intel Atom (Baytrail-I) SoC's, slave devices connected on
> HSUART1/2 ports are described by the ACPI BIOS as virtual hardware using
> HID's INT3511/INT3512 [1].
> 
> As a consequence, HW manufacturers have complete freedom to install any
> devices on-board as long as they can be accessed over serial tty
> interface. Once such device is Dell Edge 3002 IoT Gateway which sports
> ZigBee & GPS devices on the HS-UART ports 1 & 2 respectively.
> 
> In kernels before the introduction of 'Serial Device Bus (serdev)'
> subsystem, these devices were accessible using /dev/ttySx nodes. But,
> kernels since 4.15 can no longer do so.
> 
> Post 4.15, with CONFIG_SERIAL_DEV_BUS=y, serdev port controller driver
> handles the enumeration for the slaves connected on these ports. Also,
> /dev/ttySx device nodes for these ports are no longer exposed to the
> userspace.
> 
> This patch implements a new driver which binds to the ACPI serdev slaves
> enumerated by the serdev port controller and exposes /dev/ttyHSx device
> nodes which the userspace applications can use. Otherwise, upgrades to 4.15
> or higher kernels would certainly render these devices unusable.
> 
> Considering serdev is new and evolving, this is one approach to solving
> the problem at hand. An obvious drawback is the change in the tty device
> node name from ttySx => ttyHSx, which means userspace applications have to
> be modified (I know that this is strongly discouraged).
> 
> This driver has been submitted upstream and is under review. This issue has
> been identified as a regression in 4.15 and multiple solutions are being
> explored. Meanwhile, to support customer and maintain release schedule,
> this driver needs to be in Ubuntu 4.15 based kernels.
> 
> The impact is limited to systems based on Intel Atom E38XX (Baytrail-I)
> SoC's.
> 
> More info:
> https://marc.info/?t=152455871600007&r=1&w=2
> 
> This patch is based on:
> git://git.launchpad.net/~canonical-kernel/ubuntu/+source/linux-oem/+git/bionic oem-next
> 
> [1] Enabling Multi-COM Port for Microsoft Windows OS 8.1 & 10 / IoT Core [Sec. 4.1]
> (https://www.intel.com/content/dam/www/public/us/en/documents/white-papers/enabling-multi-com-port-white-paper.pdf)
> 
> Andrey Smirnov (2):
>   serdev: Make .remove in struct serdev_device_driver optional
>   serdev: Introduce devm_serdev_device_open()
> 
> Johan Hovold (5):
>   serdev: ttyport: release tty lock sooner on open
>   serdev: ttyport: ignore carrier detect to avoid hangups
>   serdev: ttyport: do not used keyed wakeup in write_wakeup
>   serdev: do not generate modaliases for controllers
>   serdev: only match serdev devices
> 
> Shrirang Bagul (2):
>   UBUNTU: SAUCE: (no-up) Support HS-UART serdev slaves over tty
>   UBUNTU: [Config] CONFIG_HSUART_SERIAL_DEVICE=y
> 
> Ulrich Hecht (1):
>   serdev: add method to set parity
> 
>  Documentation/driver-model/devres.txt  |   3 +
>  debian.oem/config/config.common.ubuntu |   1 +
>  drivers/misc/Kconfig                   |  11 ++
>  drivers/misc/Makefile                  |   1 +
>  drivers/misc/intel-hsuart-serdev.c     | 338 +++++++++++++++++++++++++++++++++
>  drivers/tty/serdev/core.c              | 123 ++++++++----
>  drivers/tty/serdev/serdev-ttyport.c    |  32 +++-
>  include/linux/serdev.h                 |  11 ++
>  8 files changed, 478 insertions(+), 42 deletions(-)
>  create mode 100644 drivers/misc/intel-hsuart-serdev.c
> 

This got applied to bionic/oem earlier.

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