Re: [PATCH RFC 12/12] PoC: arm64: dts: imx93-11x11-frdm: add multiple vdevs

[Mathieu Poirier <mathieu.poirier@linaro.org>]

On Tue, Sep 22, 2026 at 10:19:48PM +0200, Francesco Valla wrote:
> On Tue, Sep 22, 2026 at 09:43:52AM -0600, Mathieu Poirier wrote:
> > On Wed, Sep 16, 2026 at 11:10:57PM +0200, Francesco Valla wrote:
> > > Add rings for multiple vdevs, as well as the required virtio nodes for
> > > I2C, SPI and GPIO functionalities. On top of that, add example
> > > peripherals using all of them.
> > > 
> > > NOTE: this is a Proof-Of-Concept, not meant to be integrated!
> > > 
> > > Signed-off-by: Francesco Valla <francesco@valla.it>
> > > ---
> > >  arch/arm64/boot/dts/freescale/imx93-11x11-frdm.dts | 128 +++++++++++++++++++--
> > >  1 file changed, 119 insertions(+), 9 deletions(-)
> > > 
> > > diff --git a/arch/arm64/boot/dts/freescale/imx93-11x11-frdm.dts b/arch/arm64/boot/dts/freescale/imx93-11x11-frdm.dts
> > > index bd14ba28690c..dfa3b122ac5f 100644
> > > --- a/arch/arm64/boot/dts/freescale/imx93-11x11-frdm.dts
> > > +++ b/arch/arm64/boot/dts/freescale/imx93-11x11-frdm.dts
> > > @@ -53,6 +53,32 @@ button-k3 {
> > >  		};
> > >  	};
> > >  
> > > +	gpio-keys-virtio {
> > > +		compatible = "gpio-keys-polled";
> > > +		poll-interval = <100>;
> > > +
> > > +		button-v1 {
> > > +			label = "Button V1";
> > > +			linux,code = <BTN_3>;
> > > +			gpios = <&v_gpio 23 GPIO_ACTIVE_LOW>;
> > > +		};
> > > +
> > > +		button-v2 {
> > > +			label = "Button V2";
> > > +			linux,code = <BTN_4>;
> > > +			gpios = <&v_gpio 24 GPIO_ACTIVE_LOW>;
> > > +		};
> > > +	};
> > > +
> > > +	leds {
> > > +		compatible = "gpio-leds";
> > > +
> > > +		led {
> > > +			gpios = <&v_gpio 18 GPIO_ACTIVE_HIGH>;
> > > +			label = "LED V";
> > > +		};
> > > +	};
> > > +
> > >  	reg_usdhc2_vmmc: regulator-usdhc2 {
> > >  		compatible = "regulator-fixed";
> > >  		off-on-delay-us = <12000>;
> > > @@ -89,11 +115,6 @@ linux,cma {
> > >  			linux,cma-default;
> > >  		};
> > >  
> > > -		rsc_table: rsc-table@2021e000 {
> > > -			reg = <0 0x2021e000 0 0x1000>;
> > > -			no-map;
> > > -		};
> > > -
> > 
> > Why is the resource table removed?  There is no mention of that in the
> > changelog...
> >
> 
> You are obviously right, the commit message here should have been a
> poem, not a form of hermetic poetry. My bad.
> 
> The resource table here is causing problems with how Zephyr is managing
> it at its side. If it is kept in a separate memory location and copied
> there at runtime by the remote processor firmware during its startup
> (which is the current Zephyr behavior), then there might be a race
> condition when the aforesaid firmware is loaded and started by Linux
> *and* at least one of the vdev drivers (here including rpmsg_bus) is
> built-in. In this case, the copy of the resource table done by the
> remote processor might - depending on the async execution of the two
> processors - overwrite the status bit set by the Linux driver:
> 
>   Firmware load and startup (echo start > /sys/.../state)
>                            |
> 			   |
> 			   V
>   The vdev devices get registered (by register_virtio_device())
>                            |
> 			   |
> 			   V
>   If a driver is built-in, it probes and sets the vdev status
>   inside the resource table @rsc-table.
>                            .
> 			   . (in the mean time)
> 			   .
>   The remote processor starts up and copies the resource table from its
>   dedicated section to @rsc-table.
> 
> Depending on the system load and the complexity of the firmware, the two
> operations can happen in whatever sequence, causing a race condition.

This would happen regardless of this patchset.

> 
> This is somewhat masked if vdev drivers are built as modules, as the
> devices does not probe immediately but only after the modules have been
> loaded, giving the remote processor time to start. Note that this is not
> a solution! but a workaround.
> 
> If the rsc-table node is not there, the startup logic falls back to the
> classic rproc_elf_find_loaded_rsc_table().

We can't remove @rsc-table to make a problem go away.  

> 
> This is specific to i.MX platforms [1] and is probably not normally an
> issue because - as stated in [1] - the offical SDK from NXP seems not
> to check the status inside the resource table.
> 
> > >  		vdev0vring0: vdev0vring0@a4000000 {
> > >  			reg = <0 0xa4000000 0 0x8000>;
> > >  			no-map;
> > > @@ -105,12 +126,42 @@ vdev0vring1: vdev0vring1@a4008000 {
> > >  		};
> > >  
> > >  		vdev1vring0: vdev1vring0@a4010000 {
> > > -			reg = <0 0xa4010000 0 0x8000>;
> > > +			reg = <0 0xa4010000 0 0x1000>;
> > > +			no-map;
> > > +		};
> > > +
> > > +		vdev2vring0: vdev2vring0@a4011000 {
> > > +			reg = <0 0xa4011000 0 0x2000>;
> > > +			no-map;
> > > +		};
> > > +
> > > +		vdev2vring1: vdev2vring1@a4013000 {
> > > +			reg = <0 0xa4013000 0 0x2000>;
> > > +			no-map;
> > > +		};
> > > +
> > > +		vdev3vring0: vdev3vring0@a4015000 {
> > > +			reg = <0 0xa4015000 0 0x2000>;
> > > +			no-map;
> > > +		};
> > > +
> > > +		vdev4vring0: vdev4vring0@a4017000 {
> > > +			reg = <0 0xa4017000 0 0x4000>;
> > > +			no-map;
> > > +		};
> > > +
> > > +		vdev5vring0: vdev5vring0@a401B000 {
> > > +			reg = <0 0xa401B000 0 0x2000>;
> > > +			no-map;
> > > +		};
> > > +
> > > +		vdev5vring1: vdev5vring1@a401D000 {
> > > +			reg = <0 0xa401D000 0 0x2000>;
> > >  			no-map;
> > >  		};
> > >  
> > > -		vdev1vring1: vdev1vring1@a4018000 {
> > > -			reg = <0 0xa4018000 0 0x8000>;
> > > +		vdev5vring2: vdev5vring2@a401F000 {
> > > +			reg = <0 0xa401F000 0 0x1000>;
> > >  			no-map;
> > >  		};
> > >  
> > > @@ -149,8 +200,67 @@ &cm33 {
> > >  		 <&mu1 3 1>;
> > >  	mbox-names = "tx", "rx", "rxdb";
> > >  	memory-region = <&vdevbuffer>, <&vdev0vring0>, <&vdev0vring1>,
> > > -			<&vdev1vring0>, <&vdev1vring1>, <&rsc_table>;
> > > +			<&vdev1vring0>, <&vdev2vring0>, <&vdev2vring1>,
> > > +			<&vdev3vring0>, <&vdev4vring0>,
> > > +			<&vdev5vring0>, <&vdev5vring1>, <&vdev5vring2>;
> > 
> > Who is using vdev5 vrings?  
> > 
> 
> Another thing that should have been in the commit message. Vdevs are
> defined, in the Zephyr application I am using as PoC, as follows:
> 
>  - vdev0: RPMSG (tx and rx vrings)

To be backward compatible, there has to be a way to make vdev0 defaulting to
RPMSG.  It would also be nice if bindings were define for RPMSG so that it can
show up in the list of remoteproc-virtio devices like i2c, gpio and others.


>  - vdev1: entropy (single request vring)
>  - vdev2: GPIO (request and event vrings)
>  - vdev3: I2C (single request vring)
>  - vdev4: SPI (single request vring)
>  - vdev5: CAN (tx, rx and control vrings)
> 
> vdev5 is not represented inside the devicetree because the can-virtio
> driver registers a single CAN network device and has thus no need for
> such representation.

Then why is it part of the remoteproc's memory-regions?

> 
> > >  	status = "okay";
> > > +
> > > +	virtio {
> > > +		#address-cells = <1>;
> > > +		#size-cells = <0>;
> > > +
> > > +		vdev@2 {
> > > +			reg = <2>;
> > > +
> > > +			v_gpio: gpio {
> > > +				compatible = "virtio,device29";
> > > +				gpio-controller;
> > > +				#gpio-cells = <2>;
> > > +				interrupt-controller;
> > > +				#interrupt-cells = <2>;
> > > +			};
> > > +		};
> > > +
> > > +		vdev@3 {
> > > +			reg = <3>;
> > > +
> > > +			i2c {
> > > +				compatible = "virtio,device22";
> > > +				#address-cells = <1>;
> > > +				#size-cells = <0>;
> > > +
> > > +				eeprom@50 {
> > > +					compatible = "atmel,24c1025";
> > > +					reg = <0x50>;
> > > +				};
> > > +			};
> > > +		};
> > > +
> > > +		vdev@4 {
> > > +			reg = <4>;
> > > +
> > > +			spi {
> > > +				compatible = "virtio,device2d";
> > > +				#address-cells = <1>;
> > > +				#size-cells = <0>;
> > > +
> > > +				sram@0 {
> > > +					compatible = "microchip,mchp23k256";
> > > +					reg = <0>;
> > > +					spi-max-frequency = <20000000>;
> > > +				};
> > > +
> > > +				lcd@1 {
> > > +					compatible = "adafruit,yx240qv29", "ilitek,ili9341";
> > > +					reg = <1>;
> > > +					spi-max-frequency = <10000000>;
> > > +					dc-gpios = <&v_gpio 21 GPIO_ACTIVE_HIGH>;
> > > +					reset-gpios = <&v_gpio 20 GPIO_ACTIVE_HIGH>;
> > > +					rotation = <90>;
> > > +				};
> > > +			};
> > > +		};
> > > +	};
> > >  };
> > >  
> > >  &eqos {
> > > 
> > > -- 
> > > 2.55.0
> > >
> 
> Thank you!
> 
> Regards,
> Francesco
> 
> 
> [1] https://lore.kernel.org/all/20240719-imx_rproc-v2-2-10d0268c7eb1@nxp.com/