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Date:   Mon, 9 Sep 2019 14:36:06 +0200
From:   =?utf-8?Q?Ond=C5=99ej?= Jirman <megous@megous.com>
To:     Samuel Holland <samuel@sholland.org>
Cc:     Maxime Ripard <maxime.ripard@bootlin.com>,
        Chen-Yu Tsai <wens@csie.org>,
        Jassi Brar <jassisinghbrar@gmail.com>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Corentin Labbe <clabbe.montjoie@gmail.com>,
        Vasily Khoruzhick <anarsoul@gmail.com>,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-sunxi@googlegroups.com, linux-clk@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v4 00/10] Allwinner sunxi message box support
Message-ID: <20190909123606.ezsjisxpj7747h6b@core.my.home>
Mail-Followup-To: Samuel Holland <samuel@sholland.org>,
        Maxime Ripard <maxime.ripard@bootlin.com>,
        Chen-Yu Tsai <wens@csie.org>, Jassi Brar <jassisinghbrar@gmail.com>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>, Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Corentin Labbe <clabbe.montjoie@gmail.com>,
        Vasily Khoruzhick <anarsoul@gmail.com>, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-sunxi@googlegroups.com,
        linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org
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Hi,

On Sun, Sep 08, 2019 at 10:54:17PM -0500, Samuel Holland wrote:
> 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.

Tested-by: Ondrej Jirman <megous@megous.com>

(on A83T)

> > 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.

Yeah, I've patched arm_scpi too. :)

https://megous.com/git/linux/commit/?h=tbs-5.3&id=69a0cd0093a63039ace2f763e8d82009c50ff03c

(but that's just for the test, because it breaks the existing interface for
other uses)

Anyway, using mbox-names looks like a nice solution! Thanks! Though,
arm_scpi driver has a bit more complicated existing interface, where it can use
multiple mailboxes and rotates through them after every message.

BTW, I'm slowly laboring through understanding how to get suspend to ram working
on one A83T tablet. https://xnux.eu/tablet-hacking/ Which is how I tested this
driver.

regards,
	o.

> 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
> >>
> >> _______________________________________________
> >> linux-arm-kernel mailing list
> >> linux-arm-kernel@lists.infradead.org
> >> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 
> 
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