Re: [PATCH v4 00/10] Allwinner sunxi message box support

Samuel Holland
2019-09-09T03:54:26Z

On 9/8/19 10:22 PM, Ondřej Jirman wrote:
> Hello Samuel,
>
> On Mon, Aug 19, 2019 at 10:23:01PM -0500, Samuel Holland wrote:
>> This series adds support for the "hardware message box" in sun8i, sun9i,
>> and sun50i SoCs, used for communication with the ARISC management
>> processor (the platform's equivalent of the ARM SCP). The end goal is to
>> use the arm_scpi driver as a client, communicating with firmware running
>> on the AR100 CPU, or to use the mailbox to forward NMIs that the
>> firmware picks up from R_INTC.
>>
>> Unfortunately, the ARM SCPI client no longer works with this driver
>> since it now exposes all 8 hardware FIFOs individually. The SCPI client
>> could be made to work (and I posted proof-of-concept code to that effect
>> with v1 of this series), but that is a low priority, as Linux does not
>> directly use SCPI with the current firmware version; all SCPI use goes
>> through ATF via PSCI.
>>
>> As requested in the comments to v3 of this patchset, a demo client is
>> provided in the final patch. This demo goes along with a toy firmware
>> which shows that the driver does indeed work for two-way communication
>> on all channels. To build the firmware component, run:
>
> I've tried using this driver with mainline arm_scpi driver (which is probably
> an expected future use, since crust provides SCPI interface).

If you've verified in some way that this driver works on A83T, I'd appreciate
your Tested-by, so I can send a patch for the A83T device tree node.

> The problem I've found is that arm_scpi expects message box to be
> bi-directional, but this driver provides uni-directional interface.
>
> What do you think about making this driver provide bi-directional interface?
> We could halve the number of channels to 4 and mandate TX/RX configuration
> (from main CPU's PoV) as ABI.

Funny you mention that. That's what I did originally for v1, but it got NAKed by
Maxime, Andre, and Jassi:

https://lkml.org/lkml/2018/2/28/125
https://lkml.org/lkml/2018/2/28/944

> Otherwise it's impossible to use it with the arm_scpi driver.
>
> Or do you have any other ideas? I guess arm_scpi can be fixed to add a
> property that would make it possible to use single shmem with two
> mailboxes, one for rx and one for tx, but making sun6i mailbox have
> bi-directional interface sounds easier.

Yes, you can use the existence of the mbox-names property to determine if the
driver needs one mailbox or two, as I did in this driver:

https://lkml.org/lkml/2019/3/1/789

I'll have a patch available soon that implements this for arm_scpi.

Cheers,
Samuel

> regards,
> o.
>
>> git clone https://github.com/crust-firmware/meta meta
>> git clone -b mailbox-demo https://github.com/crust-firmware/crust meta/crust
>> cd meta
>> make
>>
>> That will by default produce a U-Boot + ATF + SCP firmware image in
>> [meta/]build/pinebook/u-boot-sunxi-with-spl.bin. See the top-level
>> README.md for more information, such as cross-compiler setup.
>>
>> I've now used this driver with three separate clients over the past two
>> years, and they all work. If there are no remaining concerns with the
>> driver, I'd like it to get merged.
>>
>> Even without the driver, the clock patches (1-2) can go in at any time.
>>
>> Changes from v3:
>> - Rebased on sunxi-next
>> - Added Rob's Reviewed-by for patch 3
>> - Fixed a crash when receiving a message on a disabled channel
>> - Cleaned up some comments/formatting in the driver
>> - Fixed #mbox-cells in sunxi-h3-h5.dtsi (patch 7)
>> - Removed the irqchip example (no longer relevant to the fw design)
>> - Added a demo/example client that uses the driver and a toy firmware
>>
>> Changes from v2:
>> - Merge patches 1-3
>> - Add a comment in the code explaining the CLK_IS_CRITICAL usage
>> - Add a patch to mark the AR100 clocks as critical
>> - Use YAML for the device tree binding
>> - Include a not-for-merge example usage of the mailbox
>>
>> Changes from v1:
>> - Marked message box clocks as critical instead of hacks in the driver
>> - 8 unidirectional channels instead of 4 bidirectional pairs
>> - Use per-SoC compatible strings and an A31 fallback compatible
>> - Dropped the mailbox framework patch
>> - Include DT patches for SoCs that document the message box
>>
>> Samuel Holland (10):
>> clk: sunxi-ng: Mark msgbox clocks as critical
>> clk: sunxi-ng: Mark AR100 clocks as critical
>> dt-bindings: mailbox: Add a sunxi message box binding
>> mailbox: sunxi-msgbox: Add a new mailbox driver
>> ARM: dts: sunxi: a80: Add msgbox node
>> ARM: dts: sunxi: a83t: Add msgbox node
>> ARM: dts: sunxi: h3/h5: Add msgbox node
>> arm64: dts: allwinner: a64: Add msgbox node
>> arm64: dts: allwinner: h6: Add msgbox node
>> [DO NOT MERGE] drivers: firmware: msgbox demo
>>
>> .../mailbox/allwinner,sunxi-msgbox.yaml | 79 +++++
>> arch/arm/boot/dts/sun8i-a83t.dtsi | 10 +
>> arch/arm/boot/dts/sun9i-a80.dtsi | 10 +
>> arch/arm/boot/dts/sunxi-h3-h5.dtsi | 10 +
>> arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi | 34 ++
>> arch/arm64/boot/dts/allwinner/sun50i-h5.dtsi | 24 ++
>> arch/arm64/boot/dts/allwinner/sun50i-h6.dtsi | 10 +
>> drivers/clk/sunxi-ng/ccu-sun50i-a64.c | 3 +-
>> drivers/clk/sunxi-ng/ccu-sun50i-h6-r.c | 2 +-
>> drivers/clk/sunxi-ng/ccu-sun50i-h6.c | 3 +-
>> drivers/clk/sunxi-ng/ccu-sun8i-a23.c | 3 +-
>> drivers/clk/sunxi-ng/ccu-sun8i-a33.c | 3 +-
>> drivers/clk/sunxi-ng/ccu-sun8i-a83t.c | 3 +-
>> drivers/clk/sunxi-ng/ccu-sun8i-h3.c | 3 +-
>> drivers/clk/sunxi-ng/ccu-sun8i-r.c | 2 +-
>> drivers/clk/sunxi-ng/ccu-sun9i-a80.c | 3 +-
>> drivers/firmware/Kconfig | 6 +
>> drivers/firmware/Makefile | 1 +
>> drivers/firmware/sunxi_msgbox_demo.c | 307 +++++++++++++++++
>> drivers/mailbox/Kconfig | 10 +
>> drivers/mailbox/Makefile | 2 +
>> drivers/mailbox/sunxi-msgbox.c | 323 ++++++++++++++++++
>> 22 files changed, 842 insertions(+), 9 deletions(-)
>> create mode 100644 Documentation/devicetree/bindings/mailbox/allwinner,sunxi-msgbox.yaml
>> create mode 100644 drivers/firmware/sunxi_msgbox_demo.c
>> create mode 100644 drivers/mailbox/sunxi-msgbox.c
>>
>> --
>> 2.21.0
>>
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