tpm: Add the RNG child device

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.

No compatible string is provided because this is not available in
the binding defined by Linux. If multiple rand devices are in the
system, then some method of selecting them (other than device tree)
will need to be used, or a binding will need to be added.

Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

diff --git a/drivers/tpm/tpm-uclass.c b/drivers/tpm/tpm-uclass.c
index f67fe10..0eb35f5 100644 (file)
--- a/drivers/tpm/tpm-uclass.c
+++ b/drivers/tpm/tpm-uclass.c
@@ -9,12 +9,16 @@
 #include <common.h>
 #include <dm.h>
 #include <log.h>
-#include <linux/delay.h>
-#include <linux/unaligned/be_byteshift.h>
+#include <tpm_api.h>
 #include <tpm-v1.h>
 #include <tpm-v2.h>
+#include <dm/lists.h>
+#include <linux/delay.h>
+#include <linux/unaligned/be_byteshift.h>
 #include "tpm_internal.h"
 
+#define TPM_RNG_DRV_NAME       "tpm-rng"
+
 int tpm_open(struct udevice *dev)
 {
        struct tpm_ops *ops = tpm_get_ops(dev);
@@ -136,12 +140,36 @@ int tpm_xfer(struct udevice *dev, const uint8_t *sendbuf, size_t send_size,
        return 0;
 }
 
+static int tpm_uclass_post_probe(struct udevice *dev)
+{
+       int ret;
+       const char *drv = TPM_RNG_DRV_NAME;
+       struct udevice *child;
+
+       if (CONFIG_IS_ENABLED(TPM_RNG)) {
+               ret = device_find_first_child_by_uclass(dev, UCLASS_RNG,
+                                                       &child);
+
+               if (ret != -ENODEV) {
+                       log_debug("RNG child already added to the TPM device\n");
+                       return ret;
+               }
+
+               ret = device_bind_driver(dev, drv, TPM_RNG_DRV_NAME, &child);
+               if (ret)
+                       return log_msg_ret("bind", ret);
+       }
+
+       return 0;
+}
+
 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
+       .post_probe             = tpm_uclass_post_probe,
        .per_device_auto        = sizeof(struct tpm_chip_priv),
 };