Re: [PATCH 08/10] tpm: Add the RNG child device

[Heinrich Schuchardt]

On 2/25/22 06:45, Sughosh Ganu wrote:

On Fri, 25 Feb 2022 at 00:21, Heinrich Schuchardt <xypron.g...@gmx.de> wrote:

On 2/24/22 19:05, Sughosh Ganu wrote:

The TPM device comes with the random number generator(RNG)
functionality which is built into the TPM device. Add logic to add the
RNG child device in the TPM uclass post probe callback.

The RNG device can then be used to pass a set of random bytes to the
linux kernel, need for address space randomisation through the
EFI_RNG_PROTOCOL interface.

Signed-off-by: Sughosh Ganu <sughosh.g...@linaro.org>
---
   drivers/tpm/tpm-uclass.c | 58 +++++++++++++++++++++++++++++++++++++---
   1 file changed, 54 insertions(+), 4 deletions(-)

diff --git a/drivers/tpm/tpm-uclass.c b/drivers/tpm/tpm-uclass.c
index 8619da89d8..383cc7bc48 100644
--- a/drivers/tpm/tpm-uclass.c
+++ b/drivers/tpm/tpm-uclass.c
@@ -16,6 +16,11 @@
   #include <tpm-v2.h>
   #include "tpm_internal.h"

+#include <dm/lists.h>
+
+#define TPM_RNG1_DRV_NAME    "tpm1-rng"
+#define TPM_RNG2_DRV_NAME    "tpm2-rng"
+
   bool is_tpm1(struct udevice *dev)
   {
       return IS_ENABLED(CONFIG_TPM_V1) && tpm_get_version(dev) == TPM_V1;
@@ -147,12 +152,57 @@ int tpm_xfer(struct udevice *dev, const uint8_t *sendbuf, 
size_t send_size,
       return 0;
   }

+#if IS_ENABLED(CONFIG_TPM)

This is is superfluous.
This file is only compiled if CONFIG_$(SPL_TPL_)TPM = y.

Yes, but I want the RNG child device addition to be done only in case
of u-boot proper, not for SPL and TPM. We do not have RNG support for
the SPL/TPM boot stages. So unless someone needs to enable RNG support
for SPL/TPL stages, which I doubt, this code should run only in u-boot
proper. Thanks.

The tpm-uclass.c is never compiled in SPL or TPL. Have a look at
drivers/tpm/Kconfig. There is no CONFIG_SPL_TPM or CONFIG_TPL_TPM symbol.

Best regards

Heinrich

-sughosh

Best regards

Heinrich

+static int tpm_uclass_post_probe(struct udevice *dev)
+{
+     int ret;
+     const char *drv = is_tpm1(dev) ? TPM_RNG1_DRV_NAME : TPM_RNG2_DRV_NAME;
+     struct udevice *child;
+
+     ret = device_bind_driver(dev, drv, "tpm-rng0", &child);
+     if (ret == -ENOENT) {
+             log_err("No driver configured for tpm-rng device\n");
+             return 0;
+     }
+
+     if (ret) {
+             log_err("Unable to bind rng driver with the tpm-rng device\n");
+             return ret;
+     }
+
+     return 0;
+}
+
+static int tpm_uclass_child_pre_probe(struct udevice *dev)
+{
+     int ret;
+
+     ret = tpm_open(dev->parent);
+     if (ret == -EBUSY) {
+             log_info("TPM device already opened\n");
+     } else if (ret) {
+             log_err("Unable to open TPM device\n");
+             return ret;
+     }
+
+     ret = tpm_startup(dev->parent, TPM_ST_CLEAR);
+     if (ret)
+             log_err("Unable to start TPM device\n");
+
+     return ret;
+}
+#endif /* CONFIG_TPM */
+
   UCLASS_DRIVER(tpm) = {
-     .id             = UCLASS_TPM,
-     .name           = "tpm",
-     .flags          = DM_UC_FLAG_SEQ_ALIAS,
+     .id                     = UCLASS_TPM,
+     .name                   = "tpm",
+     .flags                  = DM_UC_FLAG_SEQ_ALIAS,
   #if CONFIG_IS_ENABLED(OF_REAL)
-     .post_bind      = dm_scan_fdt_dev,
+     .post_bind              = dm_scan_fdt_dev,
+#endif
+#if IS_ENABLED(CONFIG_TPM)
+     .post_probe             = tpm_uclass_post_probe,
+     .child_pre_probe        = tpm_uclass_child_pre_probe,
   #endif
       .per_device_auto        = sizeof(struct tpm_chip_priv),
   };