rng: nuvoton: Add NPCM7xx rng driver

Add Nuvoton BMC NPCM750 rng driver.

Signed-off-by: Jim Liu <JJLIU0@nuvoton.com>

drivers/rng/Kconfig

@@ -31,6 +31,13 @@ config RNG_MSM
 	  This driver provides support for the Random Number
 	  Generator hardware found on Qualcomm SoCs.
 
+config RNG_NPCM
+	bool "Nuvoton NPCM SoCs Random Number Generator support"
+	depends on DM_RNG
+	help
+	  Enable random number generator on NPCM SoCs.
+	  This unit can provide 750 to 1000 random bits per second
+
 config RNG_OPTEE
 	bool "OP-TEE based Random Number Generator support"
 	depends on DM_RNG && OPTEE

drivers/rng/Makefile

@@ -7,6 +7,7 @@ obj-$(CONFIG_DM_RNG) += rng-uclass.o
 obj-$(CONFIG_RNG_MESON) += meson-rng.o
 obj-$(CONFIG_RNG_SANDBOX) += sandbox_rng.o
 obj-$(CONFIG_RNG_MSM) += msm_rng.o
+obj-$(CONFIG_RNG_NPCM) += npcm_rng.o
 obj-$(CONFIG_RNG_OPTEE) += optee_rng.o
 obj-$(CONFIG_RNG_STM32MP1) += stm32mp1_rng.o
 obj-$(CONFIG_RNG_ROCKCHIP) += rockchip_rng.o

drivers/rng/npcm_rng.c

@@ -0,0 +1,156 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2022 Nuvoton Technology Corp.
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <malloc.h>
+#include <rng.h>
+#include <uboot_aes.h>
+#include <asm/io.h>
+
+#define RNGCS_RNGE              BIT(0)
+#define RNGCS_DVALID            BIT(1)
+#define RNGCS_CLKP(range)       ((0x0f & (range)) << 2)
+#define RNGMODE_M1ROSEL_VAL     (0x02) /* Ring Oscillator Select for Method I */
+
+enum {
+	RNG_CLKP_80_100_MHZ = 0x00, /*default */
+	RNG_CLKP_60_80_MHZ  = 0x01,
+	RNG_CLKP_50_60_MHZ  = 0x02,
+	RNG_CLKP_40_50_MHZ  = 0x03,
+	RNG_CLKP_30_40_MHZ  = 0x04,
+	RNG_CLKP_25_30_MHZ  = 0x05,
+	RNG_CLKP_20_25_MHZ  = 0x06,
+	RNG_CLKP_5_20_MHZ   = 0x07,
+	RNG_CLKP_2_15_MHZ   = 0x08,
+	RNG_CLKP_9_12_MHZ   = 0x09,
+	RNG_CLKP_7_9_MHZ    = 0x0A,
+	RNG_CLKP_6_7_MHZ    = 0x0B,
+	RNG_CLKP_5_6_MHZ    = 0x0C,
+	RNG_CLKP_4_5_MHZ    = 0x0D,
+	RNG_CLKP_3_4_MHZ    = 0x0E,
+	RNG_NUM_OF_CLKP
+};
+
+struct npcm_rng_regs {
+	unsigned int rngcs;
+	unsigned int rngd;
+	unsigned int rngmode;
+};
+
+struct npcm_rng_priv {
+	struct npcm_rng_regs *regs;
+};
+
+static struct npcm_rng_priv *rng_priv;
+
+void npcm_rng_init(void)
+{
+	struct npcm_rng_regs *regs = rng_priv->regs;
+	int init;
+
+	/* check if rng enabled */
+	init = readb(&regs->rngcs);
+	if ((init & RNGCS_RNGE) == 0) {
+		/* init rng */
+		writeb(RNGCS_CLKP(RNG_CLKP_20_25_MHZ) | RNGCS_RNGE, &regs->rngcs);
+		writeb(RNGMODE_M1ROSEL_VAL, &regs->rngmode);
+	}
+}
+
+void npcm_rng_disable(void)
+{
+	struct npcm_rng_regs *regs = rng_priv->regs;
+
+	/* disable rng */
+	writeb(0, &regs->rngcs);
+	writeb(0, &regs->rngmode);
+}
+
+void srand(unsigned int seed)
+{
+	/* no need to seed for now */
+}
+
+int npcm_rng_read(struct udevice *dev, void *data, size_t max)
+{
+	struct npcm_rng_regs *regs = rng_priv->regs;
+	int  i;
+	int ret_val = 0;
+	char *buf = data;
+
+	npcm_rng_init();
+
+	printf("NPCM HW RNG\n");
+	/* Wait for RNG done (max bytes) */
+	for (i = 0; i < max; i++) {
+		 /* wait until DVALID is set */
+		while ((readb(&regs->rngcs) & RNGCS_DVALID) == 0)
+			;
+		buf[i] = ((unsigned int)readb(&regs->rngd) & 0x000000FF);
+	}
+
+	return ret_val;
+}
+
+unsigned int rand_r(unsigned int *seedp)
+{
+	struct npcm_rng_regs *regs = rng_priv->regs;
+	int  i;
+	unsigned int ret_val = 0;
+
+	npcm_rng_init();
+
+	/* Wait for RNG done (4 bytes) */
+	for (i = 0; i < 4 ; i++) {
+		/* wait until DVALID is set */
+		while ((readb(&regs->rngcs) & RNGCS_DVALID) == 0)
+			;
+		ret_val |= (((unsigned int)readb(&regs->rngd) & 0x000000FF) << (i * 8));
+	}
+
+	return ret_val;
+}
+
+unsigned int rand(void)
+{
+	return rand_r(NULL);
+}
+
+static int npcm_rng_bind(struct udevice *dev)
+{
+	rng_priv = calloc(1, sizeof(struct npcm_rng_priv));
+	if (!rng_priv)
+		return -ENOMEM;
+
+	rng_priv->regs = dev_remap_addr_index(dev, 0);
+	if (!rng_priv->regs) {
+		printf("Cannot find rng reg address, binding failed\n");
+		return -EINVAL;
+	}
+
+	printf("RNG: NPCM RNG module bind OK\n");
+
+	return 0;
+}
+
+static const struct udevice_id npcm_rng_ids[] = {
+	{ .compatible = "nuvoton,npcm845-rng" },
+	{ .compatible = "nuvoton,npcm750-rng" },
+	{ }
+};
+
+static const struct dm_rng_ops npcm_rng_ops = {
+	.read = npcm_rng_read,
+};
+
+U_BOOT_DRIVER(npcm_rng) = {
+	.name = "npcm_rng",
+	.id = UCLASS_RNG,
+	.ops = &npcm_rng_ops,
+	.of_match = npcm_rng_ids,
+	.priv_auto = sizeof(struct npcm_rng_priv),
+	.bind = npcm_rng_bind,
+};