hwrng: iproc-rng200: Add BCM2838 support

The HWRNG on the BCM2838 is compatible to iproc-rng200, so add the
support to this driver instead of bcm2835-rng.

Signed-off-by: Stefan Wahren <[email protected]>

hwrng: iproc-rng200: Correct SoC name

The Pi 4 SoC is called BCM2711, not BCM2838.

Fixes: "hwrng: iproc-rng200: Add BCM2838 support"

Signed-off-by: Phil Elwell <[email protected]>

drivers/char/hw_random/Kconfig

@@ -104,7 +104,7 @@ config HW_RANDOM_IPROC_RNG200
 	default HW_RANDOM
 	help
 	  This driver provides kernel-side support for the RNG200
-	  hardware found on the Broadcom iProc and STB SoCs.
+	  hardware found on the Broadcom iProc, BCM2711 and STB SoCs.
 
 	  To compile this driver as a module, choose M here: the
 	  module will be called iproc-rng200

drivers/char/hw_random/iproc-rng200.c

@@ -14,30 +14,39 @@
 #include <linux/module.h>
 #include <linux/of_address.h>
 #include <linux/of_platform.h>
+#include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/delay.h>
 
 /* Registers */
 #define RNG_CTRL_OFFSET					0x00
 #define RNG_CTRL_RNG_RBGEN_MASK				0x00001FFF
 #define RNG_CTRL_RNG_RBGEN_ENABLE			0x00000001
+#define RNG_CTRL_RNG_DIV_CTRL_SHIFT			13
 
 #define RNG_SOFT_RESET_OFFSET				0x04
 #define RNG_SOFT_RESET					0x00000001
 
 #define RBG_SOFT_RESET_OFFSET				0x08
 #define RBG_SOFT_RESET					0x00000001
 
+#define RNG_TOTAL_BIT_COUNT_OFFSET			0x0C
+
+#define RNG_TOTAL_BIT_COUNT_THRESHOLD_OFFSET		0x10
+
 #define RNG_INT_STATUS_OFFSET				0x18
 #define RNG_INT_STATUS_MASTER_FAIL_LOCKOUT_IRQ_MASK	0x80000000
 #define RNG_INT_STATUS_STARTUP_TRANSITIONS_MET_IRQ_MASK	0x00020000
 #define RNG_INT_STATUS_NIST_FAIL_IRQ_MASK		0x00000020
 #define RNG_INT_STATUS_TOTAL_BITS_COUNT_IRQ_MASK	0x00000001
 
+#define RNG_INT_ENABLE_OFFSET				0x1C
+
 #define RNG_FIFO_DATA_OFFSET				0x20
 
 #define RNG_FIFO_COUNT_OFFSET				0x24
 #define RNG_FIFO_COUNT_RNG_FIFO_COUNT_MASK		0x000000FF
+#define RNG_FIFO_COUNT_RNG_FIFO_THRESHOLD_SHIFT		8
 
 struct iproc_rng200_dev {
 	struct hwrng rng;
@@ -158,6 +167,64 @@ static int iproc_rng200_init(struct hwrng *rng)
 	return 0;
 }
 
+static int bcm2711_rng200_read(struct hwrng *rng, void *buf, size_t max,
+			       bool wait)
+{
+	struct iproc_rng200_dev *priv = to_rng_priv(rng);
+	u32 max_words = max / sizeof(u32);
+	u32 num_words, count, val;
+
+	/* ensure warm up period has elapsed */
+	while (1) {
+		val = ioread32(priv->base + RNG_TOTAL_BIT_COUNT_OFFSET);
+		if (val > 16)
+			break;
+		cpu_relax();
+	}
+
+	/* ensure fifo is not empty */
+	while (1) {
+		num_words = ioread32(priv->base + RNG_FIFO_COUNT_OFFSET) &
+			    RNG_FIFO_COUNT_RNG_FIFO_COUNT_MASK;
+		if (num_words)
+			break;
+		if (!wait)
+			return 0;
+		cpu_relax();
+	}
+
+	if (num_words > max_words)
+		num_words = max_words;
+
+	for (count = 0; count < num_words; count++) {
+		((u32 *)buf)[count] = ioread32(priv->base +
+					       RNG_FIFO_DATA_OFFSET);
+	}
+
+	return num_words * sizeof(u32);
+}
+
+static int bcm2711_rng200_init(struct hwrng *rng)
+{
+	struct iproc_rng200_dev *priv = to_rng_priv(rng);
+	uint32_t val;
+
+	if (ioread32(priv->base + RNG_CTRL_OFFSET) & RNG_CTRL_RNG_RBGEN_MASK)
+		return 0;
+
+	/* initial numbers generated are "less random" so will be discarded */
+	val = 0x40000;
+	iowrite32(val, priv->base + RNG_TOTAL_BIT_COUNT_THRESHOLD_OFFSET);
+	/* min fifo count to generate full interrupt */
+	val = 2 << RNG_FIFO_COUNT_RNG_FIFO_THRESHOLD_SHIFT;
+	iowrite32(val, priv->base + RNG_FIFO_COUNT_OFFSET);
+	/* enable the rng - 1Mhz sample rate */
+	val = (0x3 << RNG_CTRL_RNG_DIV_CTRL_SHIFT) | RNG_CTRL_RNG_RBGEN_MASK;
+	iowrite32(val, priv->base + RNG_CTRL_OFFSET);
+
+	return 0;
+}
+
 static void iproc_rng200_cleanup(struct hwrng *rng)
 {
 	struct iproc_rng200_dev *priv = to_rng_priv(rng);
@@ -184,11 +251,17 @@ static int iproc_rng200_probe(struct platform_device *pdev)
 
 	dev_set_drvdata(dev, priv);
 
-	priv->rng.name = "iproc-rng200";
-	priv->rng.read = iproc_rng200_read;
-	priv->rng.init = iproc_rng200_init;
+	priv->rng.name = pdev->name;
 	priv->rng.cleanup = iproc_rng200_cleanup;
 
+	if (of_device_is_compatible(dev->of_node, "brcm,bcm2711-rng200")) {
+		priv->rng.init = bcm2711_rng200_init;
+		priv->rng.read = bcm2711_rng200_read;
+	} else {
+		priv->rng.init = iproc_rng200_init;
+		priv->rng.read = iproc_rng200_read;
+	}
+
 	/* Register driver */
 	ret = devm_hwrng_register(dev, &priv->rng);
 	if (ret) {