Re: [PATCH 2/9] mailbox: arm_mhu: add driver for ARM MHU controller

[Sudeep Holla <sudeep.holla-5wv7dgnIgG8@public.gmane.org>]

On 20/11/14 12:34, Vincent Yang wrote:
> Add driver for the ARM Message-Handling-Unit (MHU).
>
> Signed-off-by: Andy Green <andy.green-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> Signed-off-by: Jassi Brar <jaswinder.singh-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> Signed-off-by: Vincent Yang <Vincent.Yang-l16TxrwUIHTQFUHtdCDX3A@public.gmane.org>
> Signed-off-by: Tetsuya Nuriya <nuriya.tetsuya-+CUm20s59erQFUHtdCDX3A@public.gmane.org>
> ---
>   .../devicetree/bindings/mailbox/arm-mhu.txt        |  33 ++++
>   drivers/mailbox/Kconfig                            |   7 +
>   drivers/mailbox/Makefile                           |   2 +
>   drivers/mailbox/arm_mhu.c                          | 196 +++++++++++++++++++++
>   4 files changed, 238 insertions(+)
>   create mode 100644 Documentation/devicetree/bindings/mailbox/arm-mhu.txt
>   create mode 100644 drivers/mailbox/arm_mhu.c
>
> diff --git a/Documentation/devicetree/bindings/mailbox/arm-mhu.txt b/Documentation/devicetree/bindings/mailbox/arm-mhu.txt
> new file mode 100644
> index 0000000..b1b9888
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mailbox/arm-mhu.txt
> @@ -0,0 +1,33 @@
> +ARM MHU Mailbox Driver
> +======================
> +
> +The ARM's Message-Handling-Unit (MHU) is a mailbox controller that has
> +3 independent channels/links to communicate with remote processor(s).

I had reviewed this before and I see not all the comments are addressed.
I had mentioned that you can't add support to _SECURE_ channel in Linux
as you need to assume Linux runs in non-secure privilege(and I gather
that's the case even on this platform from other email in the thread)

> + MHU links are hardwired on a platform. A link raises interrupt for any
> +received data. However, there is no specified way of knowing if the sent
> +data has been read by the remote. This driver assumes the sender polls
> +STAT register and the remote clears it after having read the data.

That could be design, interrupt support could be present on some
systems. The bindings should be flexible to add that support in future
if needed along with necessary code.

Regards,
Sudeep

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