Re: [PATCH v2 2/3] nvmem: stm32: add OP-TEE support for STM32MP13x

[Srinivas Kandagatla <srinivas.kandagatla@linaro.org>]

On 10/11/2022 15:45, Patrick Delaunay wrote:
> For boot with OP-TEE on STM32MP13, the communication with the secure
> world no more use STMicroelectronics SMC but communication with the
> BSEC TA, for data access (read/write) or lock operation:
> - all the request are sent to OP-TEE trusted application,
> - for upper OTP with ECC protection and with word programming only
>    each OTP are permanently locked when programmed to avoid ECC error
>    on the second write operation
> 
> Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
> ---
> 
> Changes in v2:
> - rebase series on linux-next/master
> - minor update after V1 revue
> - add missing sentinel in stm32_romem_of_match()
> - reorder function and remove prototypes for stm32_bsec_pta... functions
> - change stm32_bsec_pta_find to static
> - add return value in dev_err()
> - cleanups some comments, which can be on one line
> - remove test on priv->ctx in stm32_bsec_pta_remove
> - add missing tee_shm_free(shm) in stm32_bsec_pta_write() when
>    tee_shm_get_va failed
> - return error in stm32_bsec_pta_find when devm_add_action_or_reset failed
> - handle driver_register error in stm32_romem_init
> 
>   drivers/nvmem/stm32-romem.c | 445 +++++++++++++++++++++++++++++++++++-
>   1 file changed, 441 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/nvmem/stm32-romem.c b/drivers/nvmem/stm32-romem.c
> index d1d03c2ad081..0a0e29d09b67 100644
> --- a/drivers/nvmem/stm32-romem.c
> +++ b/drivers/nvmem/stm32-romem.c
> @@ -11,6 +11,7 @@
>   #include <linux/module.h>
>   #include <linux/nvmem-provider.h>
>   #include <linux/of_device.h>
> +#include <linux/tee_drv.h>
>   
>   /* BSEC secure service access from non-secure */
>   #define STM32_SMC_BSEC			0x82001003
> @@ -25,14 +26,401 @@
>   struct stm32_romem_cfg {
>   	int size;
>   	u8 lower;
> +	bool ta;
>   };
>   
>   struct stm32_romem_priv {
>   	void __iomem *base;
>   	struct nvmem_config cfg;
>   	u8 lower;
> +	struct device *ta;
>   };
>   
> +#if IS_ENABLED(CONFIG_OPTEE)
> +/*

...

> +
> +static const struct tee_client_device_id stm32_bsec_id_table[] = {
> +	{
> +		UUID_INIT(0x94cf71ad, 0x80e6, 0x40b5,
> +			  0xa7, 0xc6, 0x3d, 0xc5, 0x01, 0xeb, 0x28, 0x03)
> +	},
> +	{ }
> +};
> +
> +MODULE_DEVICE_TABLE(tee, stm32_bsec_id_table);
> +
> +static struct tee_client_driver stm32_bsec_pta_driver = {
> +	.id_table	= stm32_bsec_id_table,
> +	.driver		= {
> +		.name = "stm32-bsec-pta",
> +		.bus = &tee_bus_type,
> +		.probe = stm32_bsec_pta_probe,
> +		.remove = stm32_bsec_pta_remove,
> +	},
> +};
> +
> +static void stm32_bsec_put_device(void *data)
> +{
> +	put_device(data);
> +}
> +
> +static struct device *stm32_bsec_pta_find(struct device *dev)
> +{
> +	struct device *pta_dev;
> +	int ret;
> +
> +	pta_dev = driver_find_next_device(&stm32_bsec_pta_driver.driver, NULL);

This is clearly not representing the dependencies in a proper device model.


If the nvmem provider is a TEE client driver lets model it that way.. 
brining in a additional device and somehow trying to link it with TEE 
driver is  a hack.


> +
> +	if (pta_dev) {
> +		ret = devm_add_action_or_reset(dev, stm32_bsec_put_device, pta_dev);
> +		if (ret)
> +			dev_err(dev, "devm_add_action_or_reset() failed (%d)\n", ret);
> +
> +		return ERR_PTR(ret);
> +	}
> +
> +	return pta_dev;
> +}
> +
> +#else
> +static int stm32_bsec_pta_read(void *context, unsigned int offset, void *buf,
> +			       size_t bytes)
> +{
> +	pr_debug("%s: TA BSEC request without OPTEE support\n", __func__);
> +
> +	return -ENXIO;
> +}
> +
> +static int stm32_bsec_pta_write(void *context, unsigned int offset, void *buf,
> +				size_t bytes)
> +{
> +	pr_debug("%s: TA BSEC request without OPTEE support\n", __func__);
> +
> +	return -ENXIO;
> +}
> +
> +static struct device *stm32_bsec_pta_find(struct device *dev)
> +{
> +	pr_debug("%s: TA BSEC request without OPTEE support\n", __func__);
> +
> +	return NULL;
> +}
> +#endif

ifdefing inside the drvier is really ugly, please move this libary 
functions to a seperate file and add dependecy properly in Kconfig.

> +
>   static int stm32_romem_read(void *context, unsigned int offset, void *buf,
>   			    size_t bytes)
>   {
> @@ -173,15 +561,27 @@ static int stm32_romem_probe(struct platform_device *pdev)
>   	} else {
>   		priv->cfg.size = cfg->size;
>   		priv->lower = cfg->lower;
> -		priv->cfg.reg_read = stm32_bsec_read;
> -		priv->cfg.reg_write = stm32_bsec_write;
> +		if (cfg->ta) {
> +			priv->ta = stm32_bsec_pta_find(dev);
> +			/* wait for OP-TEE client driver to be up and ready */
> +			if (!priv->ta)
> +				return -EPROBE_DEFER;
> +			if (IS_ERR(priv->ta))
> +				return PTR_ERR(priv->ta);
> +
> +			priv->cfg.reg_read = stm32_bsec_pta_read;
> +			priv->cfg.reg_write = stm32_bsec_pta_write;
> +		} else {
> +			priv->cfg.reg_read = stm32_bsec_read;
> +			priv->cfg.reg_write = stm32_bsec_write;
> +		}
>   	}
>   
>   	return PTR_ERR_OR_ZERO(devm_nvmem_register(dev, &priv->cfg));
>   }
>   
>   /*
> - * STM32MP15 BSEC OTP regions: 4096 OTP bits (with 3072 effective bits)
> + * STM32MP15/13 BSEC OTP regions: 4096 OTP bits (with 3072 effective bits)
>    * => 96 x 32-bits data words
>    * - Lower: 1K bits, 2:1 redundancy, incremental bit programming
>    *   => 32 (x 32-bits) lower shadow registers = words 0 to 31
> @@ -191,6 +591,13 @@ static int stm32_romem_probe(struct platform_device *pdev)
>   static const struct stm32_romem_cfg stm32mp15_bsec_cfg = {
>   	.size = 384,
>   	.lower = 32,
> +	.ta = false,
> +};
> +
> +static const struct stm32_romem_cfg stm32mp13_bsec_cfg = {
> +	.size = 384,
> +	.lower = 32,
> +	.ta = true,
>   };
>   
>   static const struct of_device_id stm32_romem_of_match[] = {
> @@ -198,7 +605,10 @@ static const struct of_device_id stm32_romem_of_match[] = {
>   		.compatible = "st,stm32mp15-bsec",
>   		.data = (void *)&stm32mp15_bsec_cfg,
>   	}, {
> +		.compatible = "st,stm32mp13-bsec",
> +		.data = (void *)&stm32mp13_bsec_cfg,
>   	},
> +	{ /* sentinel */ },
>   };
>   MODULE_DEVICE_TABLE(of, stm32_romem_of_match);
>   
> @@ -209,7 +619,34 @@ static struct platform_driver stm32_romem_driver = {
>   		.of_match_table = of_match_ptr(stm32_romem_of_match),
>   	},
>   };
> -module_platform_driver(stm32_romem_driver);
> +
> +static int __init stm32_romem_init(void)
> +{
> +	int rc;
> +
> +	rc = platform_driver_register(&stm32_romem_driver);
> +	if (rc)
> +		return rc;
> +
> +#if IS_ENABLED(CONFIG_OPTEE)
> +	rc = driver_register(&stm32_bsec_pta_driver.driver);
> +	if (rc)
> +		platform_driver_unregister(&stm32_romem_driver);
> +#endif
> +
> +	return rc;
> +}
> +
> +static void __exit stm32_romem_exit(void)
> +{
> +	platform_driver_unregister(&stm32_romem_driver);
> +#if IS_ENABLED(CONFIG_OPTEE)
> +	driver_unregister(&stm32_bsec_pta_driver.driver);
> +#endif
> +}
> +
> +module_init(stm32_romem_init);
> +module_exit(stm32_romem_exit);
>   
>   MODULE_AUTHOR("Fabrice Gasnier <fabrice.gasnier@st.com>");
>   MODULE_DESCRIPTION("STMicroelectronics STM32 RO-MEM");