Re: [PATCH v3 00/12] serial: Add Tegra Combined UART driver

[Thierry Reding <thierry.reding@gmail.com>]

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On Wed, Nov 28, 2018 at 10:54:09AM +0100, Thierry Reding wrote:
> From: Thierry Reding <treding@nvidia.com>
> 
> Hi everyone,
> 
> this is a reworked version of Mikko's earlier proposal[0]. I've reworked
> the TCU driver itself so that it relies less on global variables as well
> as added a Kconfig option to allow the console support to be selected. I
> also fixed a couple of issues that manifested themselves as I was moving
> towards the IRQ driven mode (TCU was passing a pointer to a local
> variable which was getting stored in the mailbox's ring buffer and the
> data pointed at was becoming stale by the time the mailbox got around to
> dequeue it).
> 
> The biggest bulk of the changes is in the mailbox driver. This series
> addresses all of Jassi's comments from back at the time. One notable
> additional change is that shared mailboxes are now interrupt driven,
> which removes the need for polling mode.
> 
> Unfortunately there is still an issue because the TCU uses the mailbox
> in atomic context for both TTY and console modes, so we get a sleeping-
> while-atomic BUG when using mbox_client->tx_block = true in order to
> rate-limit mbox_send_message(). In order to work around this, I added a
> new mbox_flush() API that will allow flushing the mailbox in atomic
> context by using the mailbox controller's implementation of ->flush().
> For Tegra HSP shared mailboxes this is done by spinning on the shared
> mailbox register until the receiver has marked the mailbox as empty. I
> have been running this locally for a couple of days now and it works
> perfectly.
> 
> Furthermore this series incorporates Mikko's work in progress on
> splitting up the mailbox controllers and allowing multiple controllers
> to match on the same device tree node during mbox_request_channel().
> 
> The new mbox_flush() API introduces a build-time dependency between the
> TCU driver and the mailbox framework, so patches 1-9 would need to go
> through one tree. Patch 9 was already acked by Greg, so I would suggest
> that Jassi pick up the first 9 patches and I pick up patches 10-12 into
> the Tegra tree.
> 
> Changes in v3:
> - add a patch from Bartosz Golaszewski to use devm_kstrdup_const()
> - add a patch to use device-managed registration to simplify code
> - introduce explicit mailbox flush API
> 
> Changes in v2:
> - address all of Pekka's comments regarding shared interrupts, registers
>   that don't exist on Tegra186 and shared mailbox directionality
> - add a patch to enable the TCU in the 64-bit ARM default configuration
> 
> Thanks,
> Thierry
> 
> [0]: https://lore.kernel.org/patchwork/project/lkml/list/?series=357641
> 
> Bartosz Golaszewski (1):
>   mailbox: tegra-hsp: use devm_kstrdup_const()
> 
> Mikko Perttunen (5):
>   mailbox: Allow multiple controllers per device
>   dt-bindings: tegra186-hsp: Add shared mailboxes
>   dt-bindings: serial: Add bindings for nvidia,tegra194-tcu
>   arm64: tegra: Add nodes for TCU on Tegra194
>   arm64: tegra: Mark TCU as primary serial port on Tegra194 P2888
> 
> Thierry Reding (6):
>   mailbox: Support blocking transfers in atomic context
>   mailbox: tegra-hsp: Add support for shared mailboxes
>   mailbox: tegra-hsp: Add suspend/resume support
>   mailbox: tegra-hsp: Use device-managed registration API
>   serial: Add Tegra Combined UART driver
>   arm64: defconfig: Enable Tegra TCU
> 
>  .../bindings/mailbox/nvidia,tegra186-hsp.txt  |  30 +-
>  .../bindings/serial/nvidia,tegra194-tcu.txt   |  35 ++
>  .../arm64/boot/dts/nvidia/tegra194-p2888.dtsi |   2 +-
>  arch/arm64/boot/dts/nvidia/tegra194.dtsi      |  38 +-
>  arch/arm64/configs/defconfig                  |   1 +
>  drivers/mailbox/mailbox.c                     |  31 +-
>  drivers/mailbox/tegra-hsp.c                   | 517 +++++++++++++++---
>  drivers/tty/serial/Kconfig                    |  22 +
>  drivers/tty/serial/Makefile                   |   1 +
>  drivers/tty/serial/tegra-tcu.c                | 298 ++++++++++
>  include/dt-bindings/mailbox/tegra186-hsp.h    |  11 +
>  include/linux/mailbox_client.h                |   1 +
>  include/linux/mailbox_controller.h            |   4 +
>  include/uapi/linux/serial_core.h              |   3 +
>  14 files changed, 903 insertions(+), 91 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/serial/nvidia,tegra194-tcu.txt
>  create mode 100644 drivers/tty/serial/tegra-tcu.c

Hi Jassi,

do you have any comments on this?

Thierry

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