diff mbox series

[REVIEW] hwrng: add exynos Secure World RNG device driver

Message ID 20240328125056.1054878-1-alexey.klimov@linaro.org (mailing list archive)
State New, archived
Headers show
Series [REVIEW] hwrng: add exynos Secure World RNG device driver | expand

Commit Message

Alexey Klimov March 28, 2024, 12:50 p.m. UTC 
The Exynos TRNG device is controlled by firmware and shared between
non-secure world and secure world. Access to it is exposed via SMC
interface which is implemented here. The firmware code does
additional security checks, start-up test and some checks on resume.

This device is found, for instance, in Google Tensor GS101-family
of devices.

Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
---
 drivers/char/hw_random/Kconfig           |  12 +
 drivers/char/hw_random/Makefile          |   1 +
 drivers/char/hw_random/exynos-swd-trng.c | 423 +++++++++++++++++++++++
 3 files changed, 436 insertions(+)
 create mode 100644 drivers/char/hw_random/exynos-swd-trng.c

Comments

Krzysztof Kozlowski March 28, 2024, 5:01 p.m. UTC | #1 
On 28/03/2024 14:36, Krzysztof Kozlowski wrote:
>> +
>> +static UNIVERSAL_DEV_PM_OPS(exyswd_rng_pm_ops, exyswd_rng_suspend,
>> +			    exyswd_rng_resume, NULL);
>> +
>> +static struct platform_driver exyswd_rng_driver = {
>> +	.probe		= exyswd_rng_probe,
>> +	.remove		= exyswd_rng_remove,
>> +	.driver		= {
>> +		.name	= DRVNAME,
>> +		.owner	= THIS_MODULE,
> 
> So this was fixed ~8-10 years ago. Yet it re-appears. Please do not use
> downstream code as template.
> 
> Take upstream driver and either change it or customize it.

Alex Elder pointed out that some of my comments might not be precise or
not helping enough. Let me clarify then:

Please run all standard, open-source tools when submitting new driver,
which is:
1. Coccinelle, which points to this specific line since 2014,
2. smatch,
3. sparse,
4. checkpatch,
5. If changing bindings: dt_binding_check,
6. If changing DTS or bindings: dtbs_check.

I still did not point to specific error I see, because I would like you
to setup the tools and find it. This way you will have toolset ready for
any other submissions. I hope this will be helpful.

Thank you for your contribution.


Best regards,
Krzysztof
Krzysztof Kozlowski March 28, 2024, 5:05 p.m. UTC | #2 
On 28/03/2024 18:01, Krzysztof Kozlowski wrote:
> On 28/03/2024 14:36, Krzysztof Kozlowski wrote:
>>> +
>>> +static UNIVERSAL_DEV_PM_OPS(exyswd_rng_pm_ops, exyswd_rng_suspend,
>>> +			    exyswd_rng_resume, NULL);
>>> +
>>> +static struct platform_driver exyswd_rng_driver = {
>>> +	.probe		= exyswd_rng_probe,
>>> +	.remove		= exyswd_rng_remove,
>>> +	.driver		= {
>>> +		.name	= DRVNAME,
>>> +		.owner	= THIS_MODULE,
>>
>> So this was fixed ~8-10 years ago. Yet it re-appears. Please do not use
>> downstream code as template.
>>
>> Take upstream driver and either change it or customize it.
> 
> Alex Elder pointed out that some of my comments might not be precise or
> not helping enough. Let me clarify then:
> 
> Please run all standard, open-source tools when submitting new driver,
> which is:
> 1. Coccinelle, which points to this specific line since 2014,
> 2. smatch,
> 3. sparse,
> 4. checkpatch,
> 5. If changing bindings: dt_binding_check,
> 6. If changing DTS or bindings: dtbs_check.

And I forgot:
7. make W=1

Many of these, including W=1 above, can be with target, e.g.
	`make W=1 drivers/char/hw_random/`
to reduce the scope of tests/warnings etc.

Best regards,
Krzysztof
Gowthami Thiagarajan March 29, 2024, 7:55 a.m. UTC | #3 
On 2024-03-28 at 18:20:56, Alexey Klimov (alexey.klimov@linaro.org) wrote:
> The Exynos TRNG device is controlled by firmware and shared between
> non-secure world and secure world. Access to it is exposed via SMC
> interface which is implemented here. The firmware code does
> additional security checks, start-up test and some checks on resume.
> 
> This device is found, for instance, in Google Tensor GS101-family
> of devices.
> 
> Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
> ---
Hi Alexey Klimov,

Please find few comments inline.

>  drivers/char/hw_random/Kconfig           |  12 +
>  drivers/char/hw_random/Makefile          |   1 +
>  drivers/char/hw_random/exynos-swd-trng.c | 423 +++++++++++++++++++++++
>  3 files changed, 436 insertions(+)
>  create mode 100644 drivers/char/hw_random/exynos-swd-trng.c
> 
> diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
> index 442c40efb200..bff7c3ec129a 100644
> --- a/drivers/char/hw_random/Kconfig
> +++ b/drivers/char/hw_random/Kconfig
> @@ -479,6 +479,18 @@ config HW_RANDOM_EXYNOS
>  
>  	  If unsure, say Y.
>  
> +config HW_RANDOM_EXYNOS_SWD
> +	tristate "Exynos SWD HW random number generator support"
> +	default n
> +	help
> +	  This driver provides kernel-side support for accessing Samsung
> +	  TRNG hardware located in secure world using smc calls.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called exynos-swd-trng.
> +
> +	  If unsure, say N.
> +
>  config HW_RANDOM_OPTEE
>  	tristate "OP-TEE based Random Number Generator support"
>  	depends on OPTEE
> diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
> index 32549a1186dc..ce64929d461a 100644
> --- a/drivers/char/hw_random/Makefile
> +++ b/drivers/char/hw_random/Makefile
> @@ -15,6 +15,7 @@ obj-$(CONFIG_HW_RANDOM_N2RNG) += n2-rng.o
>  n2-rng-y := n2-drv.o n2-asm.o
>  obj-$(CONFIG_HW_RANDOM_VIA) += via-rng.o
>  obj-$(CONFIG_HW_RANDOM_EXYNOS) += exynos-trng.o
> +obj-$(CONFIG_HW_RANDOM_EXYNOS_SWD) += exynos-swd-trng.o
>  obj-$(CONFIG_HW_RANDOM_IXP4XX) += ixp4xx-rng.o
>  obj-$(CONFIG_HW_RANDOM_OMAP) += omap-rng.o
>  obj-$(CONFIG_HW_RANDOM_OMAP3_ROM) += omap3-rom-rng.o
> diff --git a/drivers/char/hw_random/exynos-swd-trng.c b/drivers/char/hw_random/exynos-swd-trng.c
> new file mode 100644
> index 000000000000..29def8e6d0b7
> --- /dev/null
> +++ b/drivers/char/hw_random/exynos-swd-trng.c
> @@ -0,0 +1,423 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * exynos-swd-trng.c - Random Number Generator driver for the exynos TRNG
> + * located in secure world
> + * Copyright (C) Linaro Ltd 2024 Alexey Klimov <alexey.klimov@linaro.org>
> + *
> + * Based on downstream driver:
> + * Copyright (C) 2018 Samsung Electronics
> + * Sehee Kim <sehi.kim@samsung.com>
> + */
> +
> +#include <linux/arm-smccc.h>
> +#include <linux/delay.h>
> +#include <linux/hw_random.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm_runtime.h>
> +
> +/* DTRNG smc */
> +#define SMC_CMD_RANDOM			(0x82001012)
> +
> +/* DTRNG smc commands */
> +#define HWRNG_INIT			(0x0)
> +#define HWRNG_EXIT			(0x1)
> +#define HWRNG_GET_DATA			(0x2)
> +#define HWRNG_RESUME			(0x3)
> +
> +#define HWRNG_RET_OK			0
> +#define HWRNG_RET_INVALID_ERROR		1
> +#define HWRNG_RET_RETRY_ERROR		2
> +#define HWRNG_RET_INVALID_FLAG_ERROR	3
> +#define HWRNG_RET_TEST_ERROR		4
> +#define HWRNG_RET_START_UP_TEST_DONE	5
> +#define HWRNG_RET_TEST_KAT_ERROR	0xC
> +
> +#define EXYRNG_START_UP_SIZE		(4096 + 1)
> +#define EXYRNG_RETRY_MAX_COUNT		1000000
> +#define EXYRNG_START_UP_TEST_MAX_RETRY	2
> +
> +#define DRVNAME	"exynos_swd_trng"
> +
> +enum state {
> +	INACTIVE = 0,
> +	ACTIVE,
> +};
> +
> +struct exyswd_rng {
> +	struct hwrng rng;
> +	enum state state;
> +	struct device *dev;
> +	/* to track and protect state of the device */
> +	struct mutex lock;
> +};
> +
> +static int __exynos_cm_smc(u64 *arg0, u64 *arg1,
> +			   u64 *arg2, u64 *arg3)
> +{
> +	struct arm_smccc_res res;
> +
> +	arm_smccc_smc(*arg0, *arg1, *arg2, *arg3, 0, 0, 0, 0, &res);
> +
> +	*arg0 = res.a0;
> +	*arg1 = res.a1;
> +	*arg2 = res.a2;
> +	*arg3 = res.a3;
> +
> +	return *arg0;
> +}
> +
> +static int exynos_cm_cmd(int cmd)
> +{
> +	u64 reg0, reg1, reg2, reg3;
> +
> +	reg0 = SMC_CMD_RANDOM;
> +	reg1 = cmd;
> +	reg3 = reg2 = 0;
> +
> +	return __exynos_cm_smc(&reg0, &reg1, &reg2, &reg3);
> +}
> +
> +static int exynos_cm_get_data(u64 *arg0, u64 *arg1,
> +			      u64 *arg2, u64 *arg3)
> +{
> +	*arg0 = SMC_CMD_RANDOM;
> +	*arg1 = HWRNG_GET_DATA;
> +	*arg3 = 0;
> +
> +	return __exynos_cm_smc(arg0, arg1, arg2, arg3);
> +}

Can you avoid implementing specific SMC calls in this driver?
Instead, is it possible to use arm_smccc_1_1_invoke passing
corresponding arguements?

> +
> +static int exynos_swd_get_data(u64 *arg0, u64 *arg1, u64 *arg2, u64 *arg3,
> +			       struct exyswd_rng *exyswd_rng)
> +{
> +	u32 retry_cnt = 0;
> +	int ret;
> +
> +	while (retry_cnt++ < EXYRNG_RETRY_MAX_COUNT) {
> +		ret = exynos_cm_get_data(arg0, arg1, arg2, arg3);
> +
> +		if (ret == HWRNG_RET_OK)
> +			return 0;
> +
> +		if (ret == HWRNG_RET_RETRY_ERROR) {
> +			usleep_range(50, 100);
> +			continue;
> +		}
> +
> +		if (ret == HWRNG_RET_TEST_ERROR) {
> +			dev_dbg(exyswd_rng->dev, "error while testing\n");
> +			return -EAGAIN;
> +		}
> +
> +		return -EFAULT;
> +	}
> +
> +	ret = -EFAULT;
> +	dev_warn(exyswd_rng->dev, "retry counter is reached\n");
> +	return ret;
> +}
> +
> +static int exynos_swd_init(void)
> +{
> +	u32 retry_cnt = 0;
> +	int ret;
> +
> +	do {
> +		ret = exynos_cm_cmd(HWRNG_INIT);
> +		if (ret == HWRNG_RET_RETRY_ERROR) {
> +			if (retry_cnt++ > EXYRNG_RETRY_MAX_COUNT)
> +				break;
> +
> +			usleep_range(50, 100);
> +		}
> +	} while (ret == HWRNG_RET_RETRY_ERROR);
> +
> +	return ret;
> +}
> +
> +static void exynos_swd_exit(void)
> +{
> +	u32 retry_cnt = 0;
> +
> +	while (retry_cnt++ < EXYRNG_RETRY_MAX_COUNT) {
> +		if (!exynos_cm_cmd(HWRNG_EXIT))
> +			break;
> +		usleep_range(50, 100);
> +	}
> +}
> +
> +static int exynos_swd_startup_test(struct exyswd_rng *exyswd_rng)
> +{
> +	u64 reg0, reg1, reg2, reg3;
> +	int start_up_size = EXYRNG_START_UP_SIZE;
> +	u32 retry_cnt = 0;
> +	int ret;
> +
> +	ret = exynos_swd_init();
> +	if (ret != HWRNG_RET_OK) {
> +		if (ret == HWRNG_RET_TEST_ERROR) {
> +			ret = -EAGAIN;
> +			goto out;
> +		} else
> +			return -EFAULT;
> +	}
> +
> +	while (start_up_size > 0) {
> +		/* For start-up test the 3-rd argument has to be set to 1 */
> +		reg2 = 1;

Can this be changed to a #define constant for better clarity?

> +		ret = exynos_cm_get_data(&reg0, &reg1, &reg2, &reg3);
> +		if (ret == HWRNG_RET_RETRY_ERROR) {
> +			if (retry_cnt++ > EXYRNG_RETRY_MAX_COUNT) {
> +				dev_warn(exyswd_rng->dev,
> +					 "exceeded retry in start-up test\n");
> +				break;
> +			}
> +			usleep_range(50, 100);
> +			continue;
> +		}
> +
> +		if (ret == HWRNG_RET_TEST_ERROR ||
> +		    ret == HWRNG_RET_TEST_KAT_ERROR) {
> +			dev_err(exyswd_rng->dev,
> +				"malfunction of TRNG(HW) is detected\n");
> +			return -EFAULT;
> +		}
> +
> +		if (ret == HWRNG_RET_START_UP_TEST_DONE) {
> +			dev_dbg(exyswd_rng->dev,
> +				"start-up test is already done\n");
> +			ret = 0;
> +			break;
> +		}
> +
> +		if (ret != HWRNG_RET_OK) {
> +			dev_dbg(exyswd_rng->dev, "failed to get random data\n");
> +			return -EFAULT;
> +		}
> +
> +		start_up_size -= 32;
Similar to the above, please change this. And why 32 bytes?

> +		retry_cnt = 0;
> +	}
> +
> +out:
> +	exynos_swd_exit();
> +	return ret;
> +}
> +
> +static int exynos_swd_read(struct hwrng *rng, void *data, size_t max, bool wait)
> +{
> +	struct exyswd_rng *exyswd_rng =
> +				container_of(rng, struct exyswd_rng, rng);
> +	u64 reg0, reg1, reg2, reg3;
> +	u32 *read_buf = data;
> +	u32 read_size = max;
> +	u32 retry_cnt;
> +	int ret = HWRNG_RET_OK;
> +
> +	mutex_lock(&exyswd_rng->lock);
> +	ret = exynos_swd_init();
> +	if (ret != HWRNG_RET_OK) {
> +		if (ret == HWRNG_RET_TEST_ERROR) {
> +			ret = -EAGAIN;
> +			goto out_locked;
> +		} else {
> +			mutex_unlock(&exyswd_rng->lock);
> +			return -EFAULT;
> +		}
> +	}
> +
> +	exyswd_rng->state = ACTIVE;
> +	mutex_unlock(&exyswd_rng->lock);
> +
> +	retry_cnt = 0;
> +	while (read_size >= 8) {
> +		reg2 = 0;
> +		ret = exynos_swd_get_data(&reg0, &reg1, &reg2, &reg3, exyswd_rng);
> +		if (ret)
> +			goto out;
> +
> +		*(u32 *)(read_buf++) = (u32)reg2;
> +		*(u32 *)(read_buf++) = (u32)reg3;
> +
> +		read_size -= 8;
> +		retry_cnt = 0;
> +	}
> +
> +	/*
> +	 * rng_buf_size is 32 bytes or cache line usually, it is unlikely
> +	 * we will have remaining bytes to read here.
> +	 */
> +	if (unlikely(read_size > 0)) {
> +		reg2 = 0;
> +		ret = exynos_swd_get_data(&reg0, &reg1, &reg2, &reg3, exyswd_rng);
> +		if (ret)
> +			goto out;
> +		if (read_size >= 4) {
> +			*(u32 *)(read_buf++) = (u32)reg2;
> +			read_size -= 4;
> +		}
> +
> +		if (read_size) {
> +			memcpy(read_buf, &reg3, read_size);
> +			read_size = 0;
> +		}
> +	}
> +
> +	ret = max;
> +out:
> +	mutex_lock(&exyswd_rng->lock);
> +out_locked:
> +	exynos_swd_exit();
> +	exyswd_rng->state = INACTIVE;
> +	mutex_unlock(&exyswd_rng->lock);
> +
> +	return ret;
> +}
> +
> +static int exyswd_rng_probe(struct platform_device *pdev)
> +{
> +	struct exyswd_rng *exyswd_rng;
> +	int ret;
> +
> +	exyswd_rng = devm_kzalloc(&pdev->dev, sizeof(*exyswd_rng), GFP_KERNEL);
> +	if (!exyswd_rng)
> +		return -ENOMEM;
> +
> +	exyswd_rng->rng.name = DRVNAME;
> +	exyswd_rng->rng.read = exynos_swd_read;
> +	exyswd_rng->rng.quality = 500;
> +	exyswd_rng->dev = &pdev->dev;
> +	exyswd_rng->state = INACTIVE;
> +	mutex_init(&exyswd_rng->lock);
> +
> +	/*
> +	 * Do the startup test first. If it works we've got the device
> +	 * and can finish probe().
> +	 */
> +	ret = exynos_swd_startup_test(exyswd_rng);
> +	if (ret) {
> +		dev_dbg(&pdev->dev, "start-up test failed\n");
> +		return -ENODEV;
> +	}
> +
> +	ret = devm_hwrng_register(&pdev->dev, &exyswd_rng->rng);
> +	if (ret)
> +		return dev_err_probe(&pdev->dev, ret,
> +				     "failed to register hwrng\n");
> +
> +	platform_set_drvdata(pdev, exyswd_rng);
> +	dev_set_drvdata(&pdev->dev, exyswd_rng);
> +
> +	dev_info(&pdev->dev, "hwrng registered\n");
> +
> +	return 0;
> +}
> +
> +static int exyswd_rng_remove(struct platform_device *pdev)
> +{
> +	struct exyswd_rng *exyswd_rng = platform_get_drvdata(pdev);
> +
> +	devm_hwrng_unregister(&pdev->dev, &exyswd_rng->rng);
> +
> +	mutex_lock(&exyswd_rng->lock);
> +	if (exyswd_rng->state == ACTIVE) {
> +		exynos_swd_exit();
> +		exyswd_rng->state = INACTIVE;
> +	}
> +	mutex_unlock(&exyswd_rng->lock);
> +
> +	return 0;
> +}
> +
> +#if defined(CONFIG_PM_SLEEP) || defined(CONFIG_PM_RUNTIME)
> +static int exyswd_rng_suspend(struct device *dev)
> +{
> +	struct exyswd_rng *exyswd_rng = dev_get_drvdata(dev);
> +	int ret = 0;
> +
> +	mutex_lock(&exyswd_rng->lock);
> +	if (exyswd_rng->state) {
> +		ret = exynos_cm_cmd(HWRNG_EXIT);
> +		if (ret != HWRNG_RET_OK)
> +			dev_warn(dev,
> +				 "failed to enter suspend, error %d\n", ret);
> +	}
> +	mutex_unlock(&exyswd_rng->lock);
> +
> +	return ret;
> +}
> +
> +static int exyswd_rng_resume(struct device *dev)
> +{
> +	struct exyswd_rng *exyswd_rng = dev_get_drvdata(dev);
> +	int ret;
> +
> +	mutex_lock(&exyswd_rng->lock);
> +	ret = exynos_cm_cmd(HWRNG_RESUME);
> +	if (ret != HWRNG_RET_OK)
> +		dev_warn(dev, "failed to resume, error %d\n", ret);
> +	if (exyswd_rng->state) {
> +		ret = exynos_cm_cmd(HWRNG_INIT);
> +		if (ret != HWRNG_RET_OK)
> +			dev_warn(dev,
> +				 "failed to init hwrng on resume, error %d\n",
> +				 ret);
> +	}
> +	mutex_unlock(&exyswd_rng->lock);
> +
> +	return ret;
> +}
> +#endif
> +
> +static UNIVERSAL_DEV_PM_OPS(exyswd_rng_pm_ops, exyswd_rng_suspend,
> +			    exyswd_rng_resume, NULL);
> +
> +static struct platform_driver exyswd_rng_driver = {
> +	.probe		= exyswd_rng_probe,
> +	.remove		= exyswd_rng_remove,
> +	.driver		= {
> +		.name	= DRVNAME,
> +		.owner	= THIS_MODULE,
> +		.pm     = &exyswd_rng_pm_ops,
> +	},
> +};
> +
> +static struct platform_device *exyswd_rng_pdev;
> +
> +static int __init exyswd_rng_init(void)
> +{
> +	int ret;
> +
> +	exyswd_rng_pdev = platform_device_register_simple(DRVNAME, -1, NULL, 0);
> +	if (IS_ERR(exyswd_rng_pdev))
> +		pr_err(DRVNAME ": could not register device: %ld\n",
> +		       PTR_ERR(exyswd_rng_pdev));
> +
> +	ret = platform_driver_register(&exyswd_rng_driver);
> +	if (ret) {
> +		platform_device_unregister(exyswd_rng_pdev);
> +		return ret;
> +	}
> +
> +	pr_info("ExyRNG driver, (c) 2014 Samsung Electronics\n");
> +
> +	return 0;
> +}
> +
> +static void __exit exyswd_rng_exit(void)
> +{
> +	platform_driver_unregister(&exyswd_rng_driver);
> +	platform_device_unregister(exyswd_rng_pdev);
> +}
> +
> +module_init(exyswd_rng_init);
> +module_exit(exyswd_rng_exit);
> +
> +MODULE_DESCRIPTION("Exynos SWD H/W Random Number Generator driver");
> +MODULE_AUTHOR("Alexey Klimov <alexey.klimov@linaro.org>");
> +MODULE_AUTHOR("Sehee Kim <sehi.kim@samsung.com>");
> +MODULE_LICENSE("GPL");
> -- 
> 2.43.0
>
diff mbox series

Patch

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index 442c40efb200..bff7c3ec129a 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -479,6 +479,18 @@  config HW_RANDOM_EXYNOS
 
 	  If unsure, say Y.
 
+config HW_RANDOM_EXYNOS_SWD
+	tristate "Exynos SWD HW random number generator support"
+	default n
+	help
+	  This driver provides kernel-side support for accessing Samsung
+	  TRNG hardware located in secure world using smc calls.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called exynos-swd-trng.
+
+	  If unsure, say N.
+
 config HW_RANDOM_OPTEE
 	tristate "OP-TEE based Random Number Generator support"
 	depends on OPTEE
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index 32549a1186dc..ce64929d461a 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -15,6 +15,7 @@  obj-$(CONFIG_HW_RANDOM_N2RNG) += n2-rng.o
 n2-rng-y := n2-drv.o n2-asm.o
 obj-$(CONFIG_HW_RANDOM_VIA) += via-rng.o
 obj-$(CONFIG_HW_RANDOM_EXYNOS) += exynos-trng.o
+obj-$(CONFIG_HW_RANDOM_EXYNOS_SWD) += exynos-swd-trng.o
 obj-$(CONFIG_HW_RANDOM_IXP4XX) += ixp4xx-rng.o
 obj-$(CONFIG_HW_RANDOM_OMAP) += omap-rng.o
 obj-$(CONFIG_HW_RANDOM_OMAP3_ROM) += omap3-rom-rng.o
diff --git a/drivers/char/hw_random/exynos-swd-trng.c b/drivers/char/hw_random/exynos-swd-trng.c
new file mode 100644
index 000000000000..29def8e6d0b7
--- /dev/null
+++ b/drivers/char/hw_random/exynos-swd-trng.c
@@ -0,0 +1,423 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * exynos-swd-trng.c - Random Number Generator driver for the exynos TRNG
+ * located in secure world
+ * Copyright (C) Linaro Ltd 2024 Alexey Klimov <alexey.klimov@linaro.org>
+ *
+ * Based on downstream driver:
+ * Copyright (C) 2018 Samsung Electronics
+ * Sehee Kim <sehi.kim@samsung.com>
+ */
+
+#include <linux/arm-smccc.h>
+#include <linux/delay.h>
+#include <linux/hw_random.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+
+/* DTRNG smc */
+#define SMC_CMD_RANDOM			(0x82001012)
+
+/* DTRNG smc commands */
+#define HWRNG_INIT			(0x0)
+#define HWRNG_EXIT			(0x1)
+#define HWRNG_GET_DATA			(0x2)
+#define HWRNG_RESUME			(0x3)
+
+#define HWRNG_RET_OK			0
+#define HWRNG_RET_INVALID_ERROR		1
+#define HWRNG_RET_RETRY_ERROR		2
+#define HWRNG_RET_INVALID_FLAG_ERROR	3
+#define HWRNG_RET_TEST_ERROR		4
+#define HWRNG_RET_START_UP_TEST_DONE	5
+#define HWRNG_RET_TEST_KAT_ERROR	0xC
+
+#define EXYRNG_START_UP_SIZE		(4096 + 1)
+#define EXYRNG_RETRY_MAX_COUNT		1000000
+#define EXYRNG_START_UP_TEST_MAX_RETRY	2
+
+#define DRVNAME	"exynos_swd_trng"
+
+enum state {
+	INACTIVE = 0,
+	ACTIVE,
+};
+
+struct exyswd_rng {
+	struct hwrng rng;
+	enum state state;
+	struct device *dev;
+	/* to track and protect state of the device */
+	struct mutex lock;
+};
+
+static int __exynos_cm_smc(u64 *arg0, u64 *arg1,
+			   u64 *arg2, u64 *arg3)
+{
+	struct arm_smccc_res res;
+
+	arm_smccc_smc(*arg0, *arg1, *arg2, *arg3, 0, 0, 0, 0, &res);
+
+	*arg0 = res.a0;
+	*arg1 = res.a1;
+	*arg2 = res.a2;
+	*arg3 = res.a3;
+
+	return *arg0;
+}
+
+static int exynos_cm_cmd(int cmd)
+{
+	u64 reg0, reg1, reg2, reg3;
+
+	reg0 = SMC_CMD_RANDOM;
+	reg1 = cmd;
+	reg3 = reg2 = 0;
+
+	return __exynos_cm_smc(&reg0, &reg1, &reg2, &reg3);
+}
+
+static int exynos_cm_get_data(u64 *arg0, u64 *arg1,
+			      u64 *arg2, u64 *arg3)
+{
+	*arg0 = SMC_CMD_RANDOM;
+	*arg1 = HWRNG_GET_DATA;
+	*arg3 = 0;
+
+	return __exynos_cm_smc(arg0, arg1, arg2, arg3);
+}
+
+static int exynos_swd_get_data(u64 *arg0, u64 *arg1, u64 *arg2, u64 *arg3,
+			       struct exyswd_rng *exyswd_rng)
+{
+	u32 retry_cnt = 0;
+	int ret;
+
+	while (retry_cnt++ < EXYRNG_RETRY_MAX_COUNT) {
+		ret = exynos_cm_get_data(arg0, arg1, arg2, arg3);
+
+		if (ret == HWRNG_RET_OK)
+			return 0;
+
+		if (ret == HWRNG_RET_RETRY_ERROR) {
+			usleep_range(50, 100);
+			continue;
+		}
+
+		if (ret == HWRNG_RET_TEST_ERROR) {
+			dev_dbg(exyswd_rng->dev, "error while testing\n");
+			return -EAGAIN;
+		}
+
+		return -EFAULT;
+	}
+
+	ret = -EFAULT;
+	dev_warn(exyswd_rng->dev, "retry counter is reached\n");
+	return ret;
+}
+
+static int exynos_swd_init(void)
+{
+	u32 retry_cnt = 0;
+	int ret;
+
+	do {
+		ret = exynos_cm_cmd(HWRNG_INIT);
+		if (ret == HWRNG_RET_RETRY_ERROR) {
+			if (retry_cnt++ > EXYRNG_RETRY_MAX_COUNT)
+				break;
+
+			usleep_range(50, 100);
+		}
+	} while (ret == HWRNG_RET_RETRY_ERROR);
+
+	return ret;
+}
+
+static void exynos_swd_exit(void)
+{
+	u32 retry_cnt = 0;
+
+	while (retry_cnt++ < EXYRNG_RETRY_MAX_COUNT) {
+		if (!exynos_cm_cmd(HWRNG_EXIT))
+			break;
+		usleep_range(50, 100);
+	}
+}
+
+static int exynos_swd_startup_test(struct exyswd_rng *exyswd_rng)
+{
+	u64 reg0, reg1, reg2, reg3;
+	int start_up_size = EXYRNG_START_UP_SIZE;
+	u32 retry_cnt = 0;
+	int ret;
+
+	ret = exynos_swd_init();
+	if (ret != HWRNG_RET_OK) {
+		if (ret == HWRNG_RET_TEST_ERROR) {
+			ret = -EAGAIN;
+			goto out;
+		} else
+			return -EFAULT;
+	}
+
+	while (start_up_size > 0) {
+		/* For start-up test the 3-rd argument has to be set to 1 */
+		reg2 = 1;
+		ret = exynos_cm_get_data(&reg0, &reg1, &reg2, &reg3);
+		if (ret == HWRNG_RET_RETRY_ERROR) {
+			if (retry_cnt++ > EXYRNG_RETRY_MAX_COUNT) {
+				dev_warn(exyswd_rng->dev,
+					 "exceeded retry in start-up test\n");
+				break;
+			}
+			usleep_range(50, 100);
+			continue;
+		}
+
+		if (ret == HWRNG_RET_TEST_ERROR ||
+		    ret == HWRNG_RET_TEST_KAT_ERROR) {
+			dev_err(exyswd_rng->dev,
+				"malfunction of TRNG(HW) is detected\n");
+			return -EFAULT;
+		}
+
+		if (ret == HWRNG_RET_START_UP_TEST_DONE) {
+			dev_dbg(exyswd_rng->dev,
+				"start-up test is already done\n");
+			ret = 0;
+			break;
+		}
+
+		if (ret != HWRNG_RET_OK) {
+			dev_dbg(exyswd_rng->dev, "failed to get random data\n");
+			return -EFAULT;
+		}
+
+		start_up_size -= 32;
+		retry_cnt = 0;
+	}
+
+out:
+	exynos_swd_exit();
+	return ret;
+}
+
+static int exynos_swd_read(struct hwrng *rng, void *data, size_t max, bool wait)
+{
+	struct exyswd_rng *exyswd_rng =
+				container_of(rng, struct exyswd_rng, rng);
+	u64 reg0, reg1, reg2, reg3;
+	u32 *read_buf = data;
+	u32 read_size = max;
+	u32 retry_cnt;
+	int ret = HWRNG_RET_OK;
+
+	mutex_lock(&exyswd_rng->lock);
+	ret = exynos_swd_init();
+	if (ret != HWRNG_RET_OK) {
+		if (ret == HWRNG_RET_TEST_ERROR) {
+			ret = -EAGAIN;
+			goto out_locked;
+		} else {
+			mutex_unlock(&exyswd_rng->lock);
+			return -EFAULT;
+		}
+	}
+
+	exyswd_rng->state = ACTIVE;
+	mutex_unlock(&exyswd_rng->lock);
+
+	retry_cnt = 0;
+	while (read_size >= 8) {
+		reg2 = 0;
+		ret = exynos_swd_get_data(&reg0, &reg1, &reg2, &reg3, exyswd_rng);
+		if (ret)
+			goto out;
+
+		*(u32 *)(read_buf++) = (u32)reg2;
+		*(u32 *)(read_buf++) = (u32)reg3;
+
+		read_size -= 8;
+		retry_cnt = 0;
+	}
+
+	/*
+	 * rng_buf_size is 32 bytes or cache line usually, it is unlikely
+	 * we will have remaining bytes to read here.
+	 */
+	if (unlikely(read_size > 0)) {
+		reg2 = 0;
+		ret = exynos_swd_get_data(&reg0, &reg1, &reg2, &reg3, exyswd_rng);
+		if (ret)
+			goto out;
+		if (read_size >= 4) {
+			*(u32 *)(read_buf++) = (u32)reg2;
+			read_size -= 4;
+		}
+
+		if (read_size) {
+			memcpy(read_buf, &reg3, read_size);
+			read_size = 0;
+		}
+	}
+
+	ret = max;
+out:
+	mutex_lock(&exyswd_rng->lock);
+out_locked:
+	exynos_swd_exit();
+	exyswd_rng->state = INACTIVE;
+	mutex_unlock(&exyswd_rng->lock);
+
+	return ret;
+}
+
+static int exyswd_rng_probe(struct platform_device *pdev)
+{
+	struct exyswd_rng *exyswd_rng;
+	int ret;
+
+	exyswd_rng = devm_kzalloc(&pdev->dev, sizeof(*exyswd_rng), GFP_KERNEL);
+	if (!exyswd_rng)
+		return -ENOMEM;
+
+	exyswd_rng->rng.name = DRVNAME;
+	exyswd_rng->rng.read = exynos_swd_read;
+	exyswd_rng->rng.quality = 500;
+	exyswd_rng->dev = &pdev->dev;
+	exyswd_rng->state = INACTIVE;
+	mutex_init(&exyswd_rng->lock);
+
+	/*
+	 * Do the startup test first. If it works we've got the device
+	 * and can finish probe().
+	 */
+	ret = exynos_swd_startup_test(exyswd_rng);
+	if (ret) {
+		dev_dbg(&pdev->dev, "start-up test failed\n");
+		return -ENODEV;
+	}
+
+	ret = devm_hwrng_register(&pdev->dev, &exyswd_rng->rng);
+	if (ret)
+		return dev_err_probe(&pdev->dev, ret,
+				     "failed to register hwrng\n");
+
+	platform_set_drvdata(pdev, exyswd_rng);
+	dev_set_drvdata(&pdev->dev, exyswd_rng);
+
+	dev_info(&pdev->dev, "hwrng registered\n");
+
+	return 0;
+}
+
+static int exyswd_rng_remove(struct platform_device *pdev)
+{
+	struct exyswd_rng *exyswd_rng = platform_get_drvdata(pdev);
+
+	devm_hwrng_unregister(&pdev->dev, &exyswd_rng->rng);
+
+	mutex_lock(&exyswd_rng->lock);
+	if (exyswd_rng->state == ACTIVE) {
+		exynos_swd_exit();
+		exyswd_rng->state = INACTIVE;
+	}
+	mutex_unlock(&exyswd_rng->lock);
+
+	return 0;
+}
+
+#if defined(CONFIG_PM_SLEEP) || defined(CONFIG_PM_RUNTIME)
+static int exyswd_rng_suspend(struct device *dev)
+{
+	struct exyswd_rng *exyswd_rng = dev_get_drvdata(dev);
+	int ret = 0;
+
+	mutex_lock(&exyswd_rng->lock);
+	if (exyswd_rng->state) {
+		ret = exynos_cm_cmd(HWRNG_EXIT);
+		if (ret != HWRNG_RET_OK)
+			dev_warn(dev,
+				 "failed to enter suspend, error %d\n", ret);
+	}
+	mutex_unlock(&exyswd_rng->lock);
+
+	return ret;
+}
+
+static int exyswd_rng_resume(struct device *dev)
+{
+	struct exyswd_rng *exyswd_rng = dev_get_drvdata(dev);
+	int ret;
+
+	mutex_lock(&exyswd_rng->lock);
+	ret = exynos_cm_cmd(HWRNG_RESUME);
+	if (ret != HWRNG_RET_OK)
+		dev_warn(dev, "failed to resume, error %d\n", ret);
+	if (exyswd_rng->state) {
+		ret = exynos_cm_cmd(HWRNG_INIT);
+		if (ret != HWRNG_RET_OK)
+			dev_warn(dev,
+				 "failed to init hwrng on resume, error %d\n",
+				 ret);
+	}
+	mutex_unlock(&exyswd_rng->lock);
+
+	return ret;
+}
+#endif
+
+static UNIVERSAL_DEV_PM_OPS(exyswd_rng_pm_ops, exyswd_rng_suspend,
+			    exyswd_rng_resume, NULL);
+
+static struct platform_driver exyswd_rng_driver = {
+	.probe		= exyswd_rng_probe,
+	.remove		= exyswd_rng_remove,
+	.driver		= {
+		.name	= DRVNAME,
+		.owner	= THIS_MODULE,
+		.pm     = &exyswd_rng_pm_ops,
+	},
+};
+
+static struct platform_device *exyswd_rng_pdev;
+
+static int __init exyswd_rng_init(void)
+{
+	int ret;
+
+	exyswd_rng_pdev = platform_device_register_simple(DRVNAME, -1, NULL, 0);
+	if (IS_ERR(exyswd_rng_pdev))
+		pr_err(DRVNAME ": could not register device: %ld\n",
+		       PTR_ERR(exyswd_rng_pdev));
+
+	ret = platform_driver_register(&exyswd_rng_driver);
+	if (ret) {
+		platform_device_unregister(exyswd_rng_pdev);
+		return ret;
+	}
+
+	pr_info("ExyRNG driver, (c) 2014 Samsung Electronics\n");
+
+	return 0;
+}
+
+static void __exit exyswd_rng_exit(void)
+{
+	platform_driver_unregister(&exyswd_rng_driver);
+	platform_device_unregister(exyswd_rng_pdev);
+}
+
+module_init(exyswd_rng_init);
+module_exit(exyswd_rng_exit);
+
+MODULE_DESCRIPTION("Exynos SWD H/W Random Number Generator driver");
+MODULE_AUTHOR("Alexey Klimov <alexey.klimov@linaro.org>");
+MODULE_AUTHOR("Sehee Kim <sehi.kim@samsung.com>");
+MODULE_LICENSE("GPL");