crypto/fsl: add RNG support

Register the random number generator with the rng subsystem in u-boot.
This way it can be used by EFI as well as for the 'rng' command.

Signed-off-by: Michael Walle <michael@walle.cc>
Tested-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>

drivers/crypto/fsl/rng.c

@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2020 Michael Walle <michael@walle.cc>
+ *
+ * Driver for Freescale Cryptographic Accelerator and Assurance
+ * Module (CAAM) hardware random number generator.
+ */
+
+#include <asm/cache.h>
+#include <common.h>
+#include <cpu_func.h>
+#include <dm.h>
+#include <rng.h>
+#include <linux/kernel.h>
+#include "desc_constr.h"
+#include "jobdesc.h"
+#include "jr.h"
+
+#define CAAM_RNG_MAX_FIFO_STORE_SIZE 16
+#define CAAM_RNG_DESC_LEN (3 * CAAM_CMD_SZ + CAAM_PTR_SZ)
+
+struct caam_rng_priv {
+	u32 desc[CAAM_RNG_DESC_LEN / 4];
+	u8 data[CAAM_RNG_MAX_FIFO_STORE_SIZE] __aligned(ARCH_DMA_MINALIGN);
+};
+
+static int caam_rng_read_one(struct caam_rng_priv *priv)
+{
+	int size = ALIGN(CAAM_RNG_MAX_FIFO_STORE_SIZE, ARCH_DMA_MINALIGN);
+	int ret;
+
+	ret = run_descriptor_jr(priv->desc);
+	if (ret < 0)
+		return -EIO;
+
+	invalidate_dcache_range((unsigned long)priv->data,
+				(unsigned long)priv->data + size);
+
+	return 0;
+}
+
+static int caam_rng_read(struct udevice *dev, void *data, size_t len)
+{
+	struct caam_rng_priv *priv = dev_get_priv(dev);
+	u8 *buffer = data;
+	size_t size;
+	int ret;
+
+	while (len) {
+		ret = caam_rng_read_one(priv);
+		if (ret)
+			return ret;
+
+		size = min(len, (size_t)CAAM_RNG_MAX_FIFO_STORE_SIZE);
+
+		memcpy(buffer, priv->data, size);
+		buffer += size;
+		len -= size;
+	}
+
+	return 0;
+}
+
+static int caam_rng_probe(struct udevice *dev)
+{
+	struct caam_rng_priv *priv = dev_get_priv(dev);
+	ulong size = ALIGN(CAAM_RNG_DESC_LEN, ARCH_DMA_MINALIGN);
+
+	inline_cnstr_jobdesc_rng(priv->desc, priv->data,
+				 CAAM_RNG_MAX_FIFO_STORE_SIZE);
+	flush_dcache_range((unsigned long)priv->desc,
+			   (unsigned long)priv->desc + size);
+
+	return 0;
+}
+
+static const struct dm_rng_ops caam_rng_ops = {
+	.read = caam_rng_read,
+};
+
+U_BOOT_DRIVER(caam_rng) = {
+	.name = "caam-rng",
+	.id = UCLASS_RNG,
+	.ops = &caam_rng_ops,
+	.probe = caam_rng_probe,
+	.priv_auto_alloc_size = sizeof(struct caam_rng_priv),
+	.flags = DM_FLAG_ALLOC_PRIV_DMA,
+};