[PATCH v6 2/7] tpm: rng: Add driver model interface for TPM RNG device

[Sughosh Ganu]

The TPM device has a builtin random number generator(RNG)
functionality. Expose the RNG functions of the TPM device to the
driver model so that they can be used by the EFI_RNG_PROTOCOL if the
protocol is installed.

Also change the function arguments and return type of the random
number functions to comply with the driver model api.

Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org>
---
Changes since V5:
* Use the dev_get_parent() interface for getting the TPM device when
  calling the tpm_get_random() function

 drivers/rng/Kconfig   | 11 +++++++++++
 drivers/rng/Makefile  |  1 +
 drivers/rng/tpm_rng.c | 23 +++++++++++++++++++++++
 lib/Kconfig           |  1 +
 lib/tpm-v1.c          | 13 +++++++------
 lib/tpm-v2.c          |  6 +++---
 lib/tpm_api.c         |  6 +++---
 7 files changed, 49 insertions(+), 12 deletions(-)
 create mode 100644 drivers/rng/tpm_rng.c

diff --git a/drivers/rng/Kconfig b/drivers/rng/Kconfig
index c10f7d345b..67c65311c7 100644
--- a/drivers/rng/Kconfig
+++ b/drivers/rng/Kconfig
@@ -58,4 +58,15 @@ config RNG_IPROC200
 	depends on DM_RNG
 	help
 	  Enable random number generator for RPI4.
+
+config TPM_RNG
+	bool "Enable random number generator on TPM device"
+	depends on TPM
+	default y
+	help
+	  The TPM device has an inbuilt random number generator
+	  functionality. Enable random number generator on TPM
+	  devices.
+
+
 endif
diff --git a/drivers/rng/Makefile b/drivers/rng/Makefile
index 435b3b965a..e4ca9c4149 100644
--- a/drivers/rng/Makefile
+++ b/drivers/rng/Makefile
@@ -11,3 +11,4 @@ obj-$(CONFIG_RNG_OPTEE) += optee_rng.o
 obj-$(CONFIG_RNG_STM32MP1) += stm32mp1_rng.o
 obj-$(CONFIG_RNG_ROCKCHIP) += rockchip_rng.o
 obj-$(CONFIG_RNG_IPROC200) += iproc_rng200.o
+obj-$(CONFIG_TPM_RNG) += tpm_rng.o
diff --git a/drivers/rng/tpm_rng.c b/drivers/rng/tpm_rng.c
new file mode 100644
index 0000000000..1a5e9e2e4b
--- /dev/null
+++ b/drivers/rng/tpm_rng.c
@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2022, Linaro Limited
+ */
+
+#include <dm.h>
+#include <rng.h>
+#include <tpm_api.h>
+
+static int rng_tpm_random_read(struct udevice *dev, void *data, size_t count)
+{
+	return tpm_get_random(dev_get_parent(dev), data, count);
+}
+
+static const struct dm_rng_ops tpm_rng_ops = {
+	.read = rng_tpm_random_read,
+};
+
+U_BOOT_DRIVER(tpm_rng) = {
+	.name	= "tpm-rng",
+	.id	= UCLASS_RNG,
+	.ops	= &tpm_rng_ops,
+};
diff --git a/lib/Kconfig b/lib/Kconfig
index acc0ac081a..17efaa4c80 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -358,6 +358,7 @@ source lib/crypt/Kconfig
 config TPM
 	bool "Trusted Platform Module (TPM) Support"
 	depends on DM
+	imply DM_RNG
 	help
 	  This enables support for TPMs which can be used to provide security
 	  features for your board. The TPM can be connected via LPC or I2C
diff --git a/lib/tpm-v1.c b/lib/tpm-v1.c
index 22a769c587..f7091e5bc7 100644
--- a/lib/tpm-v1.c
+++ b/lib/tpm-v1.c
@@ -9,12 +9,13 @@
 #include <common.h>
 #include <dm.h>
 #include <log.h>
-#include <asm/unaligned.h>
-#include <u-boot/sha1.h>
 #include <tpm-common.h>
 #include <tpm-v1.h>
 #include "tpm-utils.h"
 
+#include <asm/unaligned.h>
+#include <u-boot/sha1.h>
+
 #ifdef CONFIG_TPM_AUTH_SESSIONS
 
 #ifndef CONFIG_SHA1
@@ -892,19 +893,19 @@ u32 tpm1_get_random(struct udevice *dev, void *data, u32 count)
 		if (pack_byte_string(buf, sizeof(buf), "sd",
 				     0, command, sizeof(command),
 				     length_offset, this_bytes))
-			return TPM_LIB_ERROR;
+			return -EIO;
 		err = tpm_sendrecv_command(dev, buf, response,
 					   &response_length);
 		if (err)
 			return err;
 		if (unpack_byte_string(response, response_length, "d",
 				       data_size_offset, &data_size))
-			return TPM_LIB_ERROR;
+			return -EIO;
 		if (data_size > count)
-			return TPM_LIB_ERROR;
+			return -EIO;
 		if (unpack_byte_string(response, response_length, "s",
 				       data_offset, out, data_size))
-			return TPM_LIB_ERROR;
+			return -EIO;
 
 		count -= data_size;
 		out += data_size;
diff --git a/lib/tpm-v2.c b/lib/tpm-v2.c
index 1bf627853a..abca9a14b0 100644
--- a/lib/tpm-v2.c
+++ b/lib/tpm-v2.c
@@ -585,19 +585,19 @@ u32 tpm2_get_random(struct udevice *dev, void *data, u32 count)
 		if (pack_byte_string(buf, sizeof(buf), "sw",
 				     0, command_v2, sizeof(command_v2),
 				     sizeof(command_v2), this_bytes))
-			return TPM_LIB_ERROR;
+			return -EIO;
 		err = tpm_sendrecv_command(dev, buf, response,
 					   &response_length);
 		if (err)
 			return err;
 		if (unpack_byte_string(response, response_length, "w",
 				       data_size_offset, &data_size))
-			return TPM_LIB_ERROR;
+			return -EIO;
 		if (data_size > this_bytes)
 			return TPM_LIB_ERROR;
 		if (unpack_byte_string(response, response_length, "s",
 				       data_offset, out, data_size))
-			return TPM_LIB_ERROR;
+			return -EIO;
 
 		count -= data_size;
 		out += data_size;
diff --git a/lib/tpm_api.c b/lib/tpm_api.c
index 4ac4612c81..032f383ca0 100644
--- a/lib/tpm_api.c
+++ b/lib/tpm_api.c
@@ -269,7 +269,7 @@ u32 tpm_get_random(struct udevice *dev, void *data, u32 count)
 	if (tpm_is_v1(dev))
 		return tpm1_get_random(dev, data, count);
 	else if (tpm_is_v2(dev))
-		return -ENOSYS; /* not implemented yet */
-	else
-		return -ENOSYS;
+		return tpm2_get_random(dev, data, count);
+
+	return -ENOSYS;
 }
-- 
2.25.1