[PATCH v6 3/3] hwrng: add a driver for Freescale RNGC

From: Martin Kaiser
Date: Sun Jul 23 2017 - 13:51:32 EST

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The driver is ported from Freescale's Linux git and can be
found in the

vendor/freescale/imx_2.6.35_maintain

branch.

The driver supports both RNG version C that's part of some Freescale
i.MX3 SoCs and version B that is available on i.MX2x chipsets.

Signed-off-by: Steffen Trumtrar <s.trumtrar@xxxxxxxxxxxxxx>
Signed-off-by: Martin Kaiser <martin@xxxxxxxxx>
Reviewed-by: PrasannaKumar Muralidharan <prasannatsmkumar@xxxxxxxxx>
---
Changes in v6:
- get rid of mxc: rename the .c file and the kconfig option
- update the kconfig help text
- rename structs, function names etc. from mxc_rngc to imx_rngc
- rewrite the commit message to not use mxc
- set myself as commit author so people know who to blame

Changes in v5:
- use only one completion for self test and seeding

Changes in v4:
- use readl, writel instead of the __raw versions
- move the self test to a separate function
- remove the error checks before the self test,
it'll fail when there are errors
- run the self test in the probe function, add a parameter to skip it
- read the error status register before we clear irq and error
- rewrite the irq handler to read and store error status
- helper functions for irq mask, unmask
- remove some more unused defines
- fix a bounds check in the read function
- read function: check status before the fifo level
- clean up the file header, add myself to the copyright notice

Changes in v3:
- use pdev->dev to request the irq, rngc->dev is not yet initialized
- remove unused defines for registers and fields
- use module_platform_driver_probe()
- clean up the error handling in the probe function,
disable the clock if necessary
- self-test must succeed in the first run
- check for errors after seeding, exit for errors unrelated to statistics
- set a timeout when waiting for a completion

Changes in v2:
- remove irq variable from private struct
- move devm_request_irq from mxc_rngc_init to probe
- return irq in case of error
- handle irq 0 as error

drivers/char/hw_random/Kconfig | 14 ++
drivers/char/hw_random/Makefile | 1 +
drivers/char/hw_random/imx-rngc.c | 331 ++++++++++++++++++++++++++++++++++++++
3 files changed, 346 insertions(+)
create mode 100644 drivers/char/hw_random/imx-rngc.c

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index 1b223c3..6530948 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -255,6 +255,20 @@ config HW_RANDOM_MXC_RNGA

If unsure, say Y.

+config HW_RANDOM_IMX_RNGC
+ tristate "Freescale i.MX RNGC Random Number Generator"
+ depends on ARCH_MXC
+ default HW_RANDOM
+ ---help---
+ This driver provides kernel-side support for the Random Number
+ Generator Version C hardware found on some Freescale i.MX
+ processors. Version B is also supported by this driver.
+
+ To compile this driver as a module, choose M here: the
+ module will be called imx-rngc.
+
+ If unsure, say Y.
+
config HW_RANDOM_NOMADIK
tristate "ST-Ericsson Nomadik Random Number Generator support"
depends on ARCH_NOMADIK
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index b085975..39a67de 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -20,6 +20,7 @@ obj-$(CONFIG_HW_RANDOM_PASEMI) += pasemi-rng.o
obj-$(CONFIG_HW_RANDOM_VIRTIO) += virtio-rng.o
obj-$(CONFIG_HW_RANDOM_TX4939) += tx4939-rng.o
obj-$(CONFIG_HW_RANDOM_MXC_RNGA) += mxc-rnga.o
+obj-$(CONFIG_HW_RANDOM_IMX_RNGC) += imx-rngc.o
obj-$(CONFIG_HW_RANDOM_OCTEON) += octeon-rng.o
obj-$(CONFIG_HW_RANDOM_NOMADIK) += nomadik-rng.o
obj-$(CONFIG_HW_RANDOM_PSERIES) += pseries-rng.o
diff --git a/drivers/char/hw_random/imx-rngc.c b/drivers/char/hw_random/imx-rngc.c
new file mode 100644
index 0000000..88db42d
--- /dev/null
+++ b/drivers/char/hw_random/imx-rngc.c
@@ -0,0 +1,331 @@
+/*
+ * RNG driver for Freescale RNGC
+ *
+ * Copyright (C) 2008-2012 Freescale Semiconductor, Inc.
+ * Copyright (C) 2017 Martin Kaiser <martin@xxxxxxxxx>
+ *
+ * The code contained herein is licensed under the GNU General Public
+ * License. You may obtain a copy of the GNU General Public License
+ * Version 2 or later at the following locations:
+ *
+ * http://www.opensource.org/licenses/gpl-license.html
+ * http://www.gnu.org/copyleft/gpl.html
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/platform_device.h>
+#include <linux/interrupt.h>
+#include <linux/hw_random.h>
+#include <linux/completion.h>
+#include <linux/io.h>
+
+#define RNGC_COMMAND 0x0004
+#define RNGC_CONTROL 0x0008
+#define RNGC_STATUS 0x000C
+#define RNGC_ERROR 0x0010
+#define RNGC_FIFO 0x0014
+
+#define RNGC_CMD_CLR_ERR 0x00000020
+#define RNGC_CMD_CLR_INT 0x00000010
+#define RNGC_CMD_SEED 0x00000002
+#define RNGC_CMD_SELF_TEST 0x00000001
+
+#define RNGC_CTRL_MASK_ERROR 0x00000040
+#define RNGC_CTRL_MASK_DONE 0x00000020
+
+#define RNGC_STATUS_ERROR 0x00010000
+#define RNGC_STATUS_FIFO_LEVEL_MASK 0x00000f00
+#define RNGC_STATUS_FIFO_LEVEL_SHIFT 8
+#define RNGC_STATUS_SEED_DONE 0x00000020
+#define RNGC_STATUS_ST_DONE 0x00000010
+
+#define RNGC_ERROR_STATUS_STAT_ERR 0x00000008
+
+#define RNGC_TIMEOUT 3000 /* 3 sec */
+
+
+static bool self_test = true;
+module_param(self_test, bool, 0);
+
+struct imx_rngc {
+ struct device *dev;
+ struct clk *clk;
+ void __iomem *base;
+ struct hwrng rng;
+ struct completion rng_op_done;
+ /*
+ * err_reg is written only by the irq handler and read only
+ * when interrupts are masked, we need no spinlock
+ */
+ u32 err_reg;
+};
+
+
+static inline void imx_rngc_irq_mask_clear(struct imx_rngc *rngc)
+{
+ u32 ctrl, cmd;
+
+ /* mask interrupts */
+ ctrl = readl(rngc->base + RNGC_CONTROL);
+ ctrl |= RNGC_CTRL_MASK_DONE | RNGC_CTRL_MASK_ERROR;
+ writel(ctrl, rngc->base + RNGC_CONTROL);
+
+ /*
+ * CLR_INT clears the interrupt only if there's no error
+ * CLR_ERR clear the interrupt and the error register if there
+ * is an error
+ */
+ cmd = readl(rngc->base + RNGC_COMMAND);
+ cmd |= RNGC_CMD_CLR_INT | RNGC_CMD_CLR_ERR;
+ writel(cmd, rngc->base + RNGC_COMMAND);
+}
+
+static inline void imx_rngc_irq_unmask(struct imx_rngc *rngc)
+{
+ u32 ctrl;
+
+ ctrl = readl(rngc->base + RNGC_CONTROL);
+ ctrl &= ~(RNGC_CTRL_MASK_DONE | RNGC_CTRL_MASK_ERROR);
+ writel(ctrl, rngc->base + RNGC_CONTROL);
+}
+
+static int imx_rngc_self_test(struct imx_rngc *rngc)
+{
+ u32 cmd;
+ int ret;
+
+ imx_rngc_irq_unmask(rngc);
+
+ /* run self test */
+ cmd = readl(rngc->base + RNGC_COMMAND);
+ writel(cmd | RNGC_CMD_SELF_TEST, rngc->base + RNGC_COMMAND);
+
+ ret = wait_for_completion_timeout(&rngc->rng_op_done, RNGC_TIMEOUT);
+ if (!ret) {
+ imx_rngc_irq_mask_clear(rngc);
+ return -ETIMEDOUT;
+ }
+
+ if (rngc->err_reg != 0)
+ return -EIO;
+
+ return 0;
+}
+
+static int imx_rngc_read(struct hwrng *rng, void *data, size_t max, bool wait)
+{
+ struct imx_rngc *rngc = container_of(rng, struct imx_rngc, rng);
+ unsigned int status;
+ unsigned int level;
+ int retval = 0;
+
+ while (max >= sizeof(u32)) {
+ status = readl(rngc->base + RNGC_STATUS);
+
+ /* is there some error while reading this random number? */
+ if (status & RNGC_STATUS_ERROR)
+ break;
+
+ /* how many random numbers are in FIFO? [0-16] */
+ level = (status & RNGC_STATUS_FIFO_LEVEL_MASK) >>
+ RNGC_STATUS_FIFO_LEVEL_SHIFT;
+
+ if (level) {
+ /* retrieve a random number from FIFO */
+ *(u32 *)data = readl(rngc->base + RNGC_FIFO);
+
+ retval += sizeof(u32);
+ data += sizeof(u32);
+ max -= sizeof(u32);
+ }
+ }
+
+ return retval ? retval : -EIO;
+}
+
+static irqreturn_t imx_rngc_irq(int irq, void *priv)
+{
+ struct imx_rngc *rngc = (struct imx_rngc *)priv;
+ u32 status;
+
+ /*
+ * clearing the interrupt will also clear the error register
+ * read error and status before clearing
+ */
+ status = readl(rngc->base + RNGC_STATUS);
+ rngc->err_reg = readl(rngc->base + RNGC_ERROR);
+
+ imx_rngc_irq_mask_clear(rngc);
+
+ if (status & (RNGC_STATUS_SEED_DONE | RNGC_STATUS_ST_DONE))
+ complete(&rngc->rng_op_done);
+
+ return IRQ_HANDLED;
+}
+
+static int imx_rngc_init(struct hwrng *rng)
+{
+ struct imx_rngc *rngc = container_of(rng, struct imx_rngc, rng);
+ u32 cmd;
+ int ret;
+
+ /* clear error */
+ cmd = readl(rngc->base + RNGC_COMMAND);
+ writel(cmd | RNGC_CMD_CLR_ERR, rngc->base + RNGC_COMMAND);
+
+ /* create seed, repeat while there is some statistical error */
+ do {
+ imx_rngc_irq_unmask(rngc);
+
+ /* seed creation */
+ cmd = readl(rngc->base + RNGC_COMMAND);
+ writel(cmd | RNGC_CMD_SEED, rngc->base + RNGC_COMMAND);
+
+ ret = wait_for_completion_timeout(&rngc->rng_op_done,
+ RNGC_TIMEOUT);
+
+ if (!ret) {
+ imx_rngc_irq_mask_clear(rngc);
+ return -ETIMEDOUT;
+ }
+
+ } while (rngc->err_reg == RNGC_ERROR_STATUS_STAT_ERR);
+
+ return rngc->err_reg ? -EIO : 0;
+}
+
+static int imx_rngc_probe(struct platform_device *pdev)
+{
+ struct imx_rngc *rngc;
+ struct resource *res;
+ int ret;
+ int irq;
+
+ rngc = devm_kzalloc(&pdev->dev, sizeof(*rngc), GFP_KERNEL);
+ if (!rngc)
+ return -ENOMEM;
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ rngc->base = devm_ioremap_resource(&pdev->dev, res);
+ if (IS_ERR(rngc->base))
+ return PTR_ERR(rngc->base);
+
+ rngc->clk = devm_clk_get(&pdev->dev, NULL);
+ if (IS_ERR(rngc->clk)) {
+ dev_err(&pdev->dev, "Can not get rng_clk\n");
+ return PTR_ERR(rngc->clk);
+ }
+
+ irq = platform_get_irq(pdev, 0);
+ if (irq <= 0) {
+ dev_err(&pdev->dev, "Couldn't get irq %d\n", irq);
+ return irq;
+ }
+
+ ret = clk_prepare_enable(rngc->clk);
+ if (ret)
+ return ret;
+
+ ret = devm_request_irq(&pdev->dev,
+ irq, imx_rngc_irq, 0, pdev->name, (void *)rngc);
+ if (ret) {
+ dev_err(rngc->dev, "Can't get interrupt working.\n");
+ goto err;
+ }
+
+ init_completion(&rngc->rng_op_done);
+
+ rngc->rng.name = pdev->name;
+ rngc->rng.init = imx_rngc_init;
+ rngc->rng.read = imx_rngc_read;
+
+ rngc->dev = &pdev->dev;
+ platform_set_drvdata(pdev, rngc);
+
+ imx_rngc_irq_mask_clear(rngc);
+
+ if (self_test) {
+ ret = imx_rngc_self_test(rngc);
+ if (ret) {
+ dev_err(rngc->dev, "FSL RNGC self test failed.\n");
+ goto err;
+ }
+ }
+
+ ret = hwrng_register(&rngc->rng);
+ if (ret) {
+ dev_err(&pdev->dev, "FSL RNGC registering failed (%d)\n", ret);
+ goto err;
+ }
+
+ dev_info(&pdev->dev, "Freescale RNGC registered.\n");
+ return 0;
+
+err:
+ clk_disable_unprepare(rngc->clk);
+
+ return ret;
+}
+
+static int __exit imx_rngc_remove(struct platform_device *pdev)
+{
+ struct imx_rngc *rngc = platform_get_drvdata(pdev);
+
+ hwrng_unregister(&rngc->rng);
+
+ clk_disable_unprepare(rngc->clk);
+
+ return 0;
+}
+
+#ifdef CONFIG_PM
+static int imx_rngc_suspend(struct device *dev)
+{
+ struct imx_rngc *rngc = dev_get_drvdata(dev);
+
+ clk_disable_unprepare(rngc->clk);
+
+ return 0;
+}
+
+static int imx_rngc_resume(struct device *dev)
+{
+ struct imx_rngc *rngc = dev_get_drvdata(dev);
+
+ clk_prepare_enable(rngc->clk);
+
+ return 0;
+}
+
+static const struct dev_pm_ops imx_rngc_pm_ops = {
+ .suspend = imx_rngc_suspend,
+ .resume = imx_rngc_resume,
+};
+#endif
+
+static const struct of_device_id imx_rngc_dt_ids[] = {
+ { .compatible = "fsl,imx25-rngb", .data = NULL, },
+ { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, imx_rngc_dt_ids);
+
+static struct platform_driver imx_rngc_driver = {
+ .driver = {
+ .name = "imx_rngc",
+#ifdef CONFIG_PM
+ .pm = &imx_rngc_pm_ops,
+#endif
+ .of_match_table = imx_rngc_dt_ids,
+ },
+ .remove = __exit_p(imx_rngc_remove),
+};
+
+module_platform_driver_probe(imx_rngc_driver, imx_rngc_probe);
+
+MODULE_AUTHOR("Freescale Semiconductor, Inc.");
+MODULE_DESCRIPTION("H/W RNGC driver for i.MX");
+MODULE_LICENSE("GPL");
--
2.1.4

Next message: Sandy Harris: "Re: [RFC PATCH v12 3/4] Linux Random Number Generator"
Previous message: Martin Kaiser: "[PATCH v6 1/3] Documentation: devicetree: add Freescale RNGC binding"
In reply to: Martin Kaiser: "[PATCH v6 2/3] ARM: i.MX25: add RNGB node to dtsi"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]