[PATCH 2/2] ARM: i.MX8MM: add reboot to serial download mode

[Ahmad Fatoum]

Hello Uwe,

On 03.08.21 18:59, Ahmad Fatoum wrote:
> The i.MX8MM reference manual follows long established tradition in not
> documenting BootROM magic reboot codes. For older i.MX variants, the
> values can be seen in the bmode tables of Freescale's U-Boot patches.
> 
> There are no such patches for the i.MX8M, but testing shows that
> 
> 	mw 0x30390094 0x10 ; mw 0x30390098 0x40000000
> 
> is one of the configurations that trigger serial download on next warm
> reset on an i.MX8MM. Describe this in the device tree, so
> 
> 	gpr.reboot_mode.next=serial reset -r imxwd-warm
> 
> does the right thing for that SoC.

As you are currently doing i.MX8MP serial boot work, could you apply this
series, boot barebox containing it (and the i.MX watchdog driver)
from eMMC and try out:

	mw 0x30390094 0x10 ; mw 0x30390098 0x40000000
	reset -r imxwd-warm

If the 8MP is similar enough to the 8MM in this respect, the BootROM
should fall into serial download mode despite being strapped for
eMMC.

Thanks!
Ahmad


> 
> This all might work for other i.MX8M variants as well, but the dtsi
> can be genericized later on when tested.
> 
> Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
> ---
> Cc: David Jander <david at protonic.nl>
> Cc: Lucas Stach <l.stach at pengutronix.de>
> ---
>  Documentation/boards/imx.rst   | 29 +++++++++++++++++++++++++++++
>  arch/arm/dts/imx8mm-evk.dts    |  1 +
>  arch/arm/dts/imx8mm-prt8mm.dts |  1 +
>  arch/arm/dts/imx8mm.dtsi       | 18 ++++++++++++++++++
>  4 files changed, 49 insertions(+)
>  create mode 100644 arch/arm/dts/imx8mm.dtsi
> 
> diff --git a/Documentation/boards/imx.rst b/Documentation/boards/imx.rst
> index 887b45c70881..4ce9d9808cc1 100644
> --- a/Documentation/boards/imx.rst
> +++ b/Documentation/boards/imx.rst
> @@ -83,6 +83,35 @@ The images can also always be started as second stage on the target:
>  
>    barebox at Board Name:/ bootm /mnt/tftp/barebox-freescale-imx51-babbage.img
>  
> +BootROM Reboot mode codes (bmode)
> +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> +
> +For select SoCs, barebox supports communicating an alternative boot medium
> +that BootROM should select after a warm reset::
> +
> +  barebox at FSL i.MX8MM EVK board:/ devinfo gpr.reboot_mode
> +  Driver: syscon-reboot-mode
> +  Bus: platform
> +  Parent: 30390000.reset-controller at 30390000.of
> +  Parameters:
> +    next: normal (type: enum) (values: "normal", "serial")
> +    prev: normal (type: enum) (values: "normal", "serial")
> +  Device node: /soc at 0/bus at 30000000/reset-controller at 30390000/reboot-mode
> +  reboot-mode {
> +          compatible = "barebox,syscon-reboot-mode";
> +          offset = <0x94 0x98>;
> +          mask = <0xffffffff 0x40000000>;
> +          mode-normal = <0x0 0x0>;
> +          mode-serial = <0x10 0x40000000>;
> +  };
> +
> +  barebox at FSL i.MX8MM EVK board:/ gpr.reboot_mode.next=serial reset -r imxwd-warm
> +
> +This will cause barebox to fall into serial download mode on an i.MX8MM.
> +
> +Different SoCs may have more possible reboot modes available.
> +See the section on :ref:`Reboot modes<reboot_mode>` for more information.
> +
>  High Assurance Boot
>  ^^^^^^^^^^^^^^^^^^^
>  
> diff --git a/arch/arm/dts/imx8mm-evk.dts b/arch/arm/dts/imx8mm-evk.dts
> index 1e8619ccf584..304f150307a3 100644
> --- a/arch/arm/dts/imx8mm-evk.dts
> +++ b/arch/arm/dts/imx8mm-evk.dts
> @@ -7,6 +7,7 @@
>  /dts-v1/;
>  
>  #include <arm64/freescale/imx8mm-evk.dts>
> +#include "imx8mm.dtsi"
>  
>  / {
>  	chosen {
> diff --git a/arch/arm/dts/imx8mm-prt8mm.dts b/arch/arm/dts/imx8mm-prt8mm.dts
> index bdcdd0806243..abd758f2856e 100644
> --- a/arch/arm/dts/imx8mm-prt8mm.dts
> +++ b/arch/arm/dts/imx8mm-prt8mm.dts
> @@ -7,6 +7,7 @@
>  /dts-v1/;
>  
>  #include <arm64/freescale/imx8mm.dtsi>
> +#include "imx8mm.dtsi"
>  
>  / {
>  	model = "Protonic PRT8MM";
> diff --git a/arch/arm/dts/imx8mm.dtsi b/arch/arm/dts/imx8mm.dtsi
> new file mode 100644
> index 000000000000..78bbacb2b1b2
> --- /dev/null
> +++ b/arch/arm/dts/imx8mm.dtsi
> @@ -0,0 +1,18 @@
> +// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
> +/ {
> +	aliases {
> +		gpr.reboot_mode = &reboot_mode_gpr;
> +	};
> +};
> +
> +&src {
> +	compatible = "fsl,imx8mm-src", "fsl,imx8mq-src", "syscon", "simple-mfd";
> +
> +	reboot_mode_gpr: reboot-mode {
> +		compatible = "barebox,syscon-reboot-mode";
> +		offset = <0x94>, <0x98>; /* SRC_GPR{9,10} */
> +		mask = <0xffffffff>, <0x40000000>;
> +		mode-normal = <0>, <0>;
> +		mode-serial = <0x00000010>, <0x40000000>;
> +	};
> +};
> 


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