hwrng: ks-sa - add hw_random driver

Keystone Security Accelerator module has a hardware random generator
sub-module. This commit adds the driver for this sub-module.
Signed-off-by: Vitaly Andrianov <vitalya@ti.com>
[t-kristo@ti.com: dropped one unnecessary dev_err message]
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/Kconfig

@@ -452,3 +452,10 @@ config UML_RANDOM
 	  (check your distro, or download from
 	  http://sourceforge.net/projects/gkernel/).  rngd periodically reads
 	  /dev/hwrng and injects the entropy into /dev/random.
+
+config HW_RANDOM_KEYSTONE
+	depends on ARCH_KEYSTONE
+	default HW_RANDOM
+	tristate "TI Keystone NETCP SA Hardware random number generator"
+	help
+	  This option enables Keystone's hardware random generator.

drivers/char/hw_random/Makefile

@@ -38,3 +38,4 @@ obj-$(CONFIG_HW_RANDOM_MESON) += meson-rng.o
 obj-$(CONFIG_HW_RANDOM_CAVIUM) += cavium-rng.o cavium-rng-vf.o
 obj-$(CONFIG_HW_RANDOM_MTK)	+= mtk-rng.o
 obj-$(CONFIG_HW_RANDOM_S390) += s390-trng.o
+obj-$(CONFIG_HW_RANDOM_KEYSTONE) += ks-sa-rng.o

drivers/char/hw_random/ks-sa-rng.c

+/*
+ * Random Number Generator driver for the Keystone SOC
+ *
+ * Copyright (C) 2016 Texas Instruments Incorporated - http://www.ti.com
+ *
+ * Authors:	Sandeep Nair
+ *		Vitaly Andrianov
+ *
+ * This program is free software; you can redistribute 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 that 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/hw_random.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/io.h>
+#include <linux/platform_device.h>
+#include <linux/clk.h>
+#include <linux/pm_runtime.h>
+#include <linux/err.h>
+#include <linux/regmap.h>
+#include <linux/mfd/syscon.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/delay.h>
+
+#define SA_CMD_STATUS_OFS			0x8
+
+/* TRNG enable control in SA System module*/
+#define SA_CMD_STATUS_REG_TRNG_ENABLE		BIT(3)
+
+/* TRNG start control in TRNG module */
+#define TRNG_CNTL_REG_TRNG_ENABLE		BIT(10)
+
+/* Data ready indicator in STATUS register */
+#define TRNG_STATUS_REG_READY			BIT(0)
+
+/* Data ready clear control in INTACK register */
+#define TRNG_INTACK_REG_READY			BIT(0)
+
+/*
+ * Number of samples taken to gather entropy during startup.
+ * If value is 0, the number of samples is 2^24 else
+ * equals value times 2^8.
+ */
+#define TRNG_DEF_STARTUP_CYCLES			0
+#define TRNG_CNTL_REG_STARTUP_CYCLES_SHIFT	16
+
+/*
+ * Minimum number of samples taken to regenerate entropy
+ * If value is 0, the number of samples is 2^24 else
+ * equals value times 2^6.
+ */
+#define TRNG_DEF_MIN_REFILL_CYCLES		1
+#define TRNG_CFG_REG_MIN_REFILL_CYCLES_SHIFT	0
+
+/*
+ * Maximum number of samples taken to regenerate entropy
+ * If value is 0, the number of samples is 2^24 else
+ * equals value times 2^8.
+ */
+#define TRNG_DEF_MAX_REFILL_CYCLES		0
+#define TRNG_CFG_REG_MAX_REFILL_CYCLES_SHIFT	16
+
+/* Number of CLK input cycles between samples */
+#define TRNG_DEF_CLK_DIV_CYCLES			0
+#define TRNG_CFG_REG_SAMPLE_DIV_SHIFT		8
+
+/* Maximum retries to get rng data */
+#define SA_MAX_RNG_DATA_RETRIES			5
+/* Delay between retries (in usecs) */
+#define SA_RNG_DATA_RETRY_DELAY			5
+
+struct trng_regs {
+	u32	output_l;
+	u32	output_h;
+	u32	status;
+	u32	intmask;
+	u32	intack;
+	u32	control;
+	u32	config;
+};
+
+struct ks_sa_rng {
+	struct device	*dev;
+	struct hwrng	rng;
+	struct clk	*clk;
+	struct regmap	*regmap_cfg;
+	struct trng_regs *reg_rng;
+};
+
+static int ks_sa_rng_init(struct hwrng *rng)
+{
+	u32 value;
+	struct device *dev = (struct device *)rng->priv;
+	struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
+
+	/* Enable RNG module */
+	regmap_write_bits(ks_sa_rng->regmap_cfg, SA_CMD_STATUS_OFS,
+			  SA_CMD_STATUS_REG_TRNG_ENABLE,
+			  SA_CMD_STATUS_REG_TRNG_ENABLE);
+
+	/* Configure RNG module */
+	writel(0, &ks_sa_rng->reg_rng->control);
+	value = TRNG_DEF_STARTUP_CYCLES << TRNG_CNTL_REG_STARTUP_CYCLES_SHIFT;
+	writel(value, &ks_sa_rng->reg_rng->control);
+
+	value =	(TRNG_DEF_MIN_REFILL_CYCLES <<
+		 TRNG_CFG_REG_MIN_REFILL_CYCLES_SHIFT) |
+		(TRNG_DEF_MAX_REFILL_CYCLES <<
+		 TRNG_CFG_REG_MAX_REFILL_CYCLES_SHIFT) |
+		(TRNG_DEF_CLK_DIV_CYCLES <<
+		 TRNG_CFG_REG_SAMPLE_DIV_SHIFT);
+
+	writel(value, &ks_sa_rng->reg_rng->config);
+
+	/* Disable all interrupts from TRNG */
+	writel(0, &ks_sa_rng->reg_rng->intmask);
+
+	/* Enable RNG */
+	value = readl(&ks_sa_rng->reg_rng->control);
+	value |= TRNG_CNTL_REG_TRNG_ENABLE;
+	writel(value, &ks_sa_rng->reg_rng->control);
+
+	return 0;
+}
+
+static void ks_sa_rng_cleanup(struct hwrng *rng)
+{
+	struct device *dev = (struct device *)rng->priv;
+	struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
+
+	/* Disable RNG */
+	writel(0, &ks_sa_rng->reg_rng->control);
+	regmap_write_bits(ks_sa_rng->regmap_cfg, SA_CMD_STATUS_OFS,
+			  SA_CMD_STATUS_REG_TRNG_ENABLE, 0);
+}
+
+static int ks_sa_rng_data_read(struct hwrng *rng, u32 *data)
+{
+	struct device *dev = (struct device *)rng->priv;
+	struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
+
+	/* Read random data */
+	data[0] = readl(&ks_sa_rng->reg_rng->output_l);
+	data[1] = readl(&ks_sa_rng->reg_rng->output_h);
+
+	writel(TRNG_INTACK_REG_READY, &ks_sa_rng->reg_rng->intack);
+
+	return sizeof(u32) * 2;
+}
+
+static int ks_sa_rng_data_present(struct hwrng *rng, int wait)
+{
+	struct device *dev = (struct device *)rng->priv;
+	struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
+
+	u32	ready;
+	int	j;
+
+	for (j = 0; j < SA_MAX_RNG_DATA_RETRIES; j++) {
+		ready = readl(&ks_sa_rng->reg_rng->status);
+		ready &= TRNG_STATUS_REG_READY;
+
+		if (ready || !wait)
+			break;
+
+		udelay(SA_RNG_DATA_RETRY_DELAY);
+	}
+
+	return ready;
+}
+
+static int ks_sa_rng_probe(struct platform_device *pdev)
+{
+	struct ks_sa_rng	*ks_sa_rng;
+	struct device		*dev = &pdev->dev;
+	int			ret;
+	struct resource		*mem;
+
+	ks_sa_rng = devm_kzalloc(dev, sizeof(*ks_sa_rng), GFP_KERNEL);
+	if (!ks_sa_rng)
+		return -ENOMEM;
+
+	ks_sa_rng->dev = dev;
+	ks_sa_rng->rng = (struct hwrng) {
+		.name = "ks_sa_hwrng",
+		.init = ks_sa_rng_init,
+		.data_read = ks_sa_rng_data_read,
+		.data_present = ks_sa_rng_data_present,
+		.cleanup = ks_sa_rng_cleanup,
+	};
+	ks_sa_rng->rng.priv = (unsigned long)dev;
+
+	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	ks_sa_rng->reg_rng = devm_ioremap_resource(dev, mem);
+	if (IS_ERR(ks_sa_rng->reg_rng))
+		return PTR_ERR(ks_sa_rng->reg_rng);
+
+	ks_sa_rng->regmap_cfg =
+		syscon_regmap_lookup_by_phandle(dev->of_node,
+						"ti,syscon-sa-cfg");
+
+	if (IS_ERR(ks_sa_rng->regmap_cfg)) {
+		dev_err(dev, "syscon_node_to_regmap failed\n");
+		return -EINVAL;
+	}
+
+	pm_runtime_enable(dev);
+	ret = pm_runtime_get_sync(dev);
+	if (ret < 0) {
+		dev_err(dev, "Failed to enable SA power-domain\n");
+		pm_runtime_disable(dev);
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, ks_sa_rng);
+
+	return devm_hwrng_register(&pdev->dev, &ks_sa_rng->rng);
+}
+
+static int ks_sa_rng_remove(struct platform_device *pdev)
+{
+	pm_runtime_put_sync(&pdev->dev);
+	pm_runtime_disable(&pdev->dev);
+
+	return 0;
+}
+
+static const struct of_device_id ks_sa_rng_dt_match[] = {
+	{
+		.compatible = "ti,keystone-rng",
+	},
+	{ },
+};
+MODULE_DEVICE_TABLE(of, ks_sa_rng_dt_match);
+
+static struct platform_driver ks_sa_rng_driver = {
+	.driver		= {
+		.name	= "ks-sa-rng",
+		.of_match_table = ks_sa_rng_dt_match,
+	},
+	.probe		= ks_sa_rng_probe,
+	.remove		= ks_sa_rng_remove,
+};
+
+module_platform_driver(ks_sa_rng_driver);
+
+MODULE_DESCRIPTION("Keystone NETCP SA H/W Random Number Generator driver");
+MODULE_AUTHOR("Vitaly Andrianov <vitalya@ti.com>");
+MODULE_LICENSE("GPL");