Re: [PATCH v4 4/4] remoteproc: stm32: Add support of an OP-TEE TA to load the firmware

[Mathieu Poirier]

On Fri, Mar 08, 2024 at 03:47:08PM +0100, Arnaud Pouliquen wrote:
> The new TEE remoteproc device is used to manage remote firmware in a
> secure, trusted context. The 'st,stm32mp1-m4-tee' compatibility is
> introduced to delegate the loading of the firmware to the trusted
> execution context. In such cases, the firmware should be signed and
> adhere to the image format defined by the TEE.
> 
> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@xxxxxxxxxxx>
> ---
> Updates from V3:
> - remove support of the attach use case. Will be addressed in a separate
>   thread,
> - add st_rproc_tee_ops::parse_fw ops,
> - inverse call of devm_rproc_alloc()and tee_rproc_register() to manage cross
>   reference between the rproc struct and the tee_rproc struct in tee_rproc.c.
> ---
>  drivers/remoteproc/stm32_rproc.c | 60 +++++++++++++++++++++++++++++---
>  1 file changed, 56 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/remoteproc/stm32_rproc.c b/drivers/remoteproc/stm32_rproc.c
> index 8cd838df4e92..13df33c78aa2 100644
> --- a/drivers/remoteproc/stm32_rproc.c
> +++ b/drivers/remoteproc/stm32_rproc.c
> @@ -20,6 +20,7 @@
>  #include <linux/remoteproc.h>
>  #include <linux/reset.h>
>  #include <linux/slab.h>
> +#include <linux/tee_remoteproc.h>
>  #include <linux/workqueue.h>
>  
>  #include "remoteproc_internal.h"
> @@ -49,6 +50,9 @@
>  #define M4_STATE_STANDBY	4
>  #define M4_STATE_CRASH		5
>  
> +/* Remote processor unique identifier aligned with the Trusted Execution Environment definitions */

Why is this the case?  At least from the kernel side it is possible to call
tee_rproc_register() with any kind of value, why is there a need to be any
kind of alignment with the TEE?

> +#define STM32_MP1_M4_PROC_ID    0
> +
>  struct stm32_syscon {
>  	struct regmap *map;
>  	u32 reg;
> @@ -257,6 +261,19 @@ static int stm32_rproc_release(struct rproc *rproc)
>  	return 0;
>  }
>  
> +static int stm32_rproc_tee_stop(struct rproc *rproc)
> +{
> +	int err;
> +
> +	stm32_rproc_request_shutdown(rproc);
> +
> +	err = tee_rproc_stop(rproc);
> +	if (err)
> +		return err;
> +
> +	return stm32_rproc_release(rproc);
> +}
> +
>  static int stm32_rproc_prepare(struct rproc *rproc)
>  {
>  	struct device *dev = rproc->dev.parent;
> @@ -693,8 +710,19 @@ static const struct rproc_ops st_rproc_ops = {
>  	.get_boot_addr	= rproc_elf_get_boot_addr,
>  };
>  
> +static const struct rproc_ops st_rproc_tee_ops = {
> +	.prepare	= stm32_rproc_prepare,
> +	.start		= tee_rproc_start,
> +	.stop		= stm32_rproc_tee_stop,
> +	.kick		= stm32_rproc_kick,
> +	.load		= tee_rproc_load_fw,
> +	.parse_fw	= tee_rproc_parse_fw,
> +	.find_loaded_rsc_table = tee_rproc_find_loaded_rsc_table,
> +};
> +
>  static const struct of_device_id stm32_rproc_match[] = {
> -	{ .compatible = "st,stm32mp1-m4" },
> +	{.compatible = "st,stm32mp1-m4",},
> +	{.compatible = "st,stm32mp1-m4-tee",},
>  	{},
>  };
>  MODULE_DEVICE_TABLE(of, stm32_rproc_match);
> @@ -853,6 +881,7 @@ static int stm32_rproc_probe(struct platform_device *pdev)
>  	struct device *dev = &pdev->dev;
>  	struct stm32_rproc *ddata;
>  	struct device_node *np = dev->of_node;
> +	struct tee_rproc *trproc = NULL;
>  	struct rproc *rproc;
>  	unsigned int state;
>  	int ret;
> @@ -861,9 +890,26 @@ static int stm32_rproc_probe(struct platform_device *pdev)
>  	if (ret)
>  		return ret;
>  
> -	rproc = devm_rproc_alloc(dev, np->name, &st_rproc_ops, NULL, sizeof(*ddata));
> -	if (!rproc)
> -		return -ENOMEM;
> +	if (of_device_is_compatible(np, "st,stm32mp1-m4-tee")) {
> +		/*
> +		 * Delegate the firmware management to the secure context.
> +		 * The firmware loaded has to be signed.
> +		 */
> +		rproc = devm_rproc_alloc(dev, np->name, &st_rproc_tee_ops, NULL, sizeof(*ddata));
> +		if (!rproc)
> +			return -ENOMEM;
> +
> +		trproc = tee_rproc_register(dev, rproc, STM32_MP1_M4_PROC_ID);
> +		if (IS_ERR(trproc)) {
> +			dev_err_probe(dev, PTR_ERR(trproc),
> +				      "signed firmware not supported by TEE\n");
> +			return PTR_ERR(trproc);
> +		}
> +	} else {
> +		rproc = devm_rproc_alloc(dev, np->name, &st_rproc_ops, NULL, sizeof(*ddata));
> +		if (!rproc)
> +			return -ENOMEM;
> +	}
>  
>  	ddata = rproc->priv;
>  
> @@ -915,6 +961,9 @@ static int stm32_rproc_probe(struct platform_device *pdev)
>  		dev_pm_clear_wake_irq(dev);
>  		device_init_wakeup(dev, false);
>  	}
> +	if (trproc)

        if (rproc->tee_interface)


I am done reviewing this set.

Thanks,
Mathieu

> +		tee_rproc_unregister(trproc);
> +
>  	return ret;
>  }
>  
> @@ -935,6 +984,9 @@ static void stm32_rproc_remove(struct platform_device *pdev)
>  		dev_pm_clear_wake_irq(dev);
>  		device_init_wakeup(dev, false);
>  	}
> +	if (rproc->tee_interface)
> +		tee_rproc_unregister(rproc->tee_interface);
> +
>  }
>  
>  static int stm32_rproc_suspend(struct device *dev)
> -- 
> 2.25.1
>