linux-kernel - Re: [RFC PATCH v2 0/9] scpi: Add SCPI registry to handle legacy protocol

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Date:	Wed, 22 Jun 2016 10:54:13 +0800
From:	Frank Wang <frank.wang@...k-chips.com>
To:	Neil Armstrong <narmstrong@...libre.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	sudeep.holla@....com
Cc:	linux-amlogic@...ts.infradead.org, khilman@...libre.com,
	heiko@...ech.de, wxt@...k-chips.com,
	Tao Huang <huangtao@...k-chips.com>, frank.wang@...k-chips.com
Subject: Re: [RFC PATCH v2 0/9] scpi: Add SCPI registry to handle legacy
 protocol

Hi Neil,

On 2016/6/21 18:02, Neil Armstrong wrote:
> This patchset aims to support the legacy SCPI firmware implementation that was
> delivered as early technology preview for the JUNO platform.
>
> Finally a stable, maintained and public implementation for the SCPI protocol
> has been upstreamed part of the JUNO support and it is the recommended way
> of implementing SCP communication on ARMv8 platforms.
>
> The Amlogic GXBB platform is using this legacy protocol, as the RK3368 & RK3399
> platforms. Only the GXBB example is provided here, but it's unclear if other
> Amlogic ARMv8 based SoCs uses this legacy procotol.
>
> In order to support the legacy protocol :
>   - Move the scpi_get_ops to a thin registry layer
>   - Change the arm_scpi.c to use the registry layer
>   - Add a separate config option to build the registry layer
>   - Add the legacy SCPI driver based on the new implementation
>   - For example, add the Amlogic GXBB MHU and SCPI DT cpufreq & sensors nodes

Two comments may be not very associated with this series.

First, do you have any plan to implement the APIs for extended set ID of 
SCPI? If these APIs do not care commands, just focus on a message 
transmission access, something like a library role, and extended command 
can define in consumers driver module, I think it can more help for 
other consumers like Rockchip to send/receive nonstandard command data 
conveniently. Can it be?

Second, As far as I know, some legacy mailbox hardware which like 
Altera, Rockchip...  need write command and data register sequentially, 
then it can create a interrupt, however, arm-scpi first use inner 
scpi_xfer structure to package the message, then data is passed to 
msg_submit (At mailbox.c), further into the bottom mailbox driver, but 
the data type is converted void*, so the mailbox driver could not 
extract the contents of message, if it do cast type, it may become 
non-general from driver view. Hence, is it possible to add a message 
header into scpi_xfer which for the bottom mailbox driver or dope out 
any other methods to solve it?

BR.
Frank

> Initial RFC discution tread can be found at https://lkml.org/lkml/2016/5/26/111
>
> Neil Armstrong (9):
>    mailbox: Add Amlogic Meson Message-Handling-Unit
>    dt-bindings: mailbox: Add Amlogic Meson MHU Bindings
>    ARM64: dts: meson-gxbb: Add Meson MHU Node
>    firmware: Add a SCPI registry to handle multiple implementations
>    firmware: scpi: Switch arm_scpi to use new registry
>    firmware: Add legacy SCPI protocol driver
>    dt-bindings: arm: Update arm,scpi bindings with Meson GXBB SCPI
>    ARM64: dts: meson-gxbb: Add SRAM node
>    ARM64: dts: meson-gxbb: Add SCPI with cpufreq & sensors Nodes
>
>   Documentation/devicetree/bindings/arm/arm,scpi.txt |   8 +-
>   .../devicetree/bindings/mailbox/meson-mhu.txt      |  33 ++
>   arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi        |  53 ++
>   drivers/firmware/Kconfig                           |  24 +
>   drivers/firmware/Makefile                          |   2 +
>   drivers/firmware/arm_scpi.c                        |  14 +-
>   drivers/firmware/legacy_scpi.c                     | 644 +++++++++++++++++++++
>   drivers/firmware/scpi.c                            |  94 +++
>   drivers/mailbox/Makefile                           |   2 +
>   drivers/mailbox/meson_mhu.c                        | 199 +++++++
>   include/linux/scpi_protocol.h                      |  15 +-
>   11 files changed, 1075 insertions(+), 13 deletions(-)
>   create mode 100644 Documentation/devicetree/bindings/mailbox/meson-mhu.txt
>   create mode 100644 drivers/firmware/legacy_scpi.c
>   create mode 100644 drivers/firmware/scpi.c
>   create mode 100644 drivers/mailbox/meson_mhu.c
>