hwrng: pic32 - Add PIC32 RNG hardware driver

Add support for the hardware true random number generator
peripheral found on PIC32.

Signed-off-by: Joshua Henderson <joshua.henderson@microchip.com>
Signed-off-by: Purna Chandra Mandal <purna.mandal@microchip.com>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

3 files changed, 169 insertions, 0 deletions

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index 8d895908d608..967904f5bbcb 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -381,6 +381,19 @@ config HW_RANDOM_STM32
 
           If unsure, say N.
 
+config HW_RANDOM_PIC32
+        tristate "Microchip PIC32 Random Number Generator support"
+        depends on HW_RANDOM && MACH_PIC32
+        default y
+        ---help---
+          This driver provides kernel-side support for the Random Number
+          Generator hardware found on a PIC32.
+
+          To compile this driver as a module, choose M here. the
+          module will be called pic32-rng.
+
+          If unsure, say Y.
+
 endif # HW_RANDOM
 
 config UML_RANDOM
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index 5ad397635128..f5a6fa7690e7 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -33,3 +33,4 @@ obj-$(CONFIG_HW_RANDOM_MSM) += msm-rng.o
 obj-$(CONFIG_HW_RANDOM_ST) += st-rng.o
 obj-$(CONFIG_HW_RANDOM_XGENE) += xgene-rng.o
 obj-$(CONFIG_HW_RANDOM_STM32) += stm32-rng.o
+obj-$(CONFIG_HW_RANDOM_PIC32) += pic32-rng.o
diff --git a/drivers/char/hw_random/pic32-rng.c b/drivers/char/hw_random/pic32-rng.c
new file mode 100644
index 000000000000..108897bea2d0
--- /dev/null
+++ b/drivers/char/hw_random/pic32-rng.c
@@ -0,0 +1,155 @@
+/*
+ * PIC32 RNG driver
+ *
+ * Joshua Henderson <joshua.henderson@microchip.com>
+ * Copyright (C) 2016 Microchip Technology Inc.  All rights reserved.
+ *
+ * This program is free software; you can distribute it and/or modify it
+ * under the terms of the GNU General Public License (Version 2) as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * for more details.
+ */
+
+#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;
+        struct clk      *clk;
+};
+
+/*
+ * 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;
+
+        if (max < 8)
+                return 0;
+
+        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 resource *res;
+        u32 v;
+        int ret;
+
+        priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+        if (!priv)
+                return -ENOMEM;
+
+        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+        priv->base = devm_ioremap_resource(&pdev->dev, res);
+        if (IS_ERR(priv->base))
+                return PTR_ERR(priv->base);
+
+        priv->clk = devm_clk_get(&pdev->dev, NULL);
+        if (IS_ERR(priv->clk))
+                return PTR_ERR(priv->clk);
+
+        ret = clk_prepare_enable(priv->clk);
+        if (ret)
+                return ret;
+
+        /* 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 = hwrng_register(&priv->rng);
+        if (ret)
+                goto err_register;
+
+        platform_set_drvdata(pdev, priv);
+
+        return 0;
+
+err_register:
+        clk_disable_unprepare(priv->clk);
+        return ret;
+}
+
+static int pic32_rng_remove(struct platform_device *pdev)
+{
+        struct pic32_rng *rng = platform_get_drvdata(pdev);
+
+        hwrng_unregister(&rng->rng);
+        writel(0, rng->base + RNGCON);
+        clk_disable_unprepare(rng->clk);
+        return 0;
+}
+
+static const struct of_device_id pic32_rng_of_match[] = {
+        { .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",
+                .owner  = THIS_MODULE,
+                .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");