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path: root/drivers/char/hw_random/pic32-rng.c
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-rw-r--r--drivers/char/hw_random/pic32-rng.c131
1 files changed, 131 insertions, 0 deletions
diff --git a/drivers/char/hw_random/pic32-rng.c b/drivers/char/hw_random/pic32-rng.c
new file mode 100644
index 000000000..e04a054e8
--- /dev/null
+++ b/drivers/char/hw_random/pic32-rng.c
@@ -0,0 +1,131 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * PIC32 RNG driver
+ *
+ * Joshua Henderson <joshua.henderson@microchip.com>
+ * Copyright (C) 2016 Microchip Technology Inc. All rights reserved.
+ */
+
+#include <linux/clk.h>
+#include <linux/clkdev.h>
+#include <linux/err.h>
+#include <linux/hw_random.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+#define RNGCON 0x04
+#define TRNGEN BIT(8)
+#define PRNGEN BIT(9)
+#define PRNGCONT BIT(10)
+#define TRNGMOD BIT(11)
+#define SEEDLOAD BIT(12)
+#define RNGPOLY1 0x08
+#define RNGPOLY2 0x0C
+#define RNGNUMGEN1 0x10
+#define RNGNUMGEN2 0x14
+#define RNGSEED1 0x18
+#define RNGSEED2 0x1C
+#define RNGRCNT 0x20
+#define RCNT_MASK 0x7F
+
+struct pic32_rng {
+ void __iomem *base;
+ struct hwrng rng;
+};
+
+/*
+ * The TRNG can generate up to 24Mbps. This is a timeout that should be safe
+ * enough given the instructions in the loop and that the TRNG may not always
+ * be at maximum rate.
+ */
+#define RNG_TIMEOUT 500
+
+static int pic32_rng_read(struct hwrng *rng, void *buf, size_t max,
+ bool wait)
+{
+ struct pic32_rng *priv = container_of(rng, struct pic32_rng, rng);
+ u64 *data = buf;
+ u32 t;
+ unsigned int timeout = RNG_TIMEOUT;
+
+ do {
+ t = readl(priv->base + RNGRCNT) & RCNT_MASK;
+ if (t == 64) {
+ /* TRNG value comes through the seed registers */
+ *data = ((u64)readl(priv->base + RNGSEED2) << 32) +
+ readl(priv->base + RNGSEED1);
+ return 8;
+ }
+ } while (wait && --timeout);
+
+ return -EIO;
+}
+
+static int pic32_rng_probe(struct platform_device *pdev)
+{
+ struct pic32_rng *priv;
+ struct clk *clk;
+ u32 v;
+ int ret;
+
+ priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ priv->base = devm_platform_ioremap_resource(pdev, 0);
+ if (IS_ERR(priv->base))
+ return PTR_ERR(priv->base);
+
+ clk = devm_clk_get_enabled(&pdev->dev, NULL);
+ if (IS_ERR(clk))
+ return PTR_ERR(clk);
+
+ /* enable TRNG in enhanced mode */
+ v = TRNGEN | TRNGMOD;
+ writel(v, priv->base + RNGCON);
+
+ priv->rng.name = pdev->name;
+ priv->rng.read = pic32_rng_read;
+
+ ret = devm_hwrng_register(&pdev->dev, &priv->rng);
+ if (ret)
+ return ret;
+
+ platform_set_drvdata(pdev, priv);
+
+ return 0;
+}
+
+static int pic32_rng_remove(struct platform_device *pdev)
+{
+ struct pic32_rng *rng = platform_get_drvdata(pdev);
+
+ writel(0, rng->base + RNGCON);
+ return 0;
+}
+
+static const struct of_device_id pic32_rng_of_match[] __maybe_unused = {
+ { .compatible = "microchip,pic32mzda-rng", },
+ { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, pic32_rng_of_match);
+
+static struct platform_driver pic32_rng_driver = {
+ .probe = pic32_rng_probe,
+ .remove = pic32_rng_remove,
+ .driver = {
+ .name = "pic32-rng",
+ .of_match_table = of_match_ptr(pic32_rng_of_match),
+ },
+};
+
+module_platform_driver(pic32_rng_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Joshua Henderson <joshua.henderson@microchip.com>");
+MODULE_DESCRIPTION("Microchip PIC32 RNG Driver");