Re: [PATCH v2 2/2] hwrng: iproc-rng200 - Add Broadcom IPROC RNG driver

From: Scott Branden
Date: Mon Mar 02 2015 - 19:51:14 EST

Hi Dmitry,

Looking at the driver based on your comments it is following models of older hwrng drivers. I will work on cleaning up based on your comments as well.

On 15-02-25 10:43 AM, Dmitry Torokhov wrote:
Hi Scott,

On Wed, Feb 25, 2015 at 10:16:24AM -0800, Scott Branden wrote:
This adds a driver for random number generator present on Broadcom
IPROC devices.

Reviewed-by: Ray Jui <rjui@xxxxxxxxxxxx>
Signed-off-by: Scott Branden <sbranden@xxxxxxxxxxxx>
---
drivers/char/hw_random/Kconfig | 13 ++
drivers/char/hw_random/Makefile | 1 +
drivers/char/hw_random/iproc-rng200.c | 239 ++++++++++++++++++++++++++++++++++
3 files changed, 253 insertions(+)
create mode 100644 drivers/char/hw_random/iproc-rng200.c

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index de57b38..f48cf11 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -101,6 +101,19 @@ config HW_RANDOM_BCM2835

If unsure, say Y.

+config HW_RANDOM_IPROC_RNG200
+ tristate "Broadcom iProc RNG200 support"
+ depends on ARCH_BCM_IPROC
+ default HW_RANDOM
+ ---help---
+ This driver provides kernel-side support for the RNG200
+ hardware found on the Broadcom iProc SoCs.
+
+ To compile this driver as a module, choose M here: the
+ module will be called iproc-rng200
+
+ If unsure, say Y.
+
config HW_RANDOM_GEODE
tristate "AMD Geode HW Random Number Generator support"
depends on X86_32 && PCI
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index 0b4cd57..055bb01 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -28,5 +28,6 @@ obj-$(CONFIG_HW_RANDOM_POWERNV) += powernv-rng.o
obj-$(CONFIG_HW_RANDOM_EXYNOS) += exynos-rng.o
obj-$(CONFIG_HW_RANDOM_TPM) += tpm-rng.o
obj-$(CONFIG_HW_RANDOM_BCM2835) += bcm2835-rng.o
+obj-$(CONFIG_HW_RANDOM_IPROC_RNG200) += iproc-rng200.o
obj-$(CONFIG_HW_RANDOM_MSM) += msm-rng.o
obj-$(CONFIG_HW_RANDOM_XGENE) += xgene-rng.o
diff --git a/drivers/char/hw_random/iproc-rng200.c b/drivers/char/hw_random/iproc-rng200.c
new file mode 100644
index 0000000..4643aa9
--- /dev/null
+++ b/drivers/char/hw_random/iproc-rng200.c
@@ -0,0 +1,239 @@
+/*
+* Copyright (C) 2014 Broadcom Corporation
+*
+* This program is free software; you can redistribute it and/or
+* modify it under the terms of the GNU General Public License as
+* published by the Free Software Foundation version 2.
+*
+* This program is distributed "as is" WITHOUT ANY WARRANTY of any
+* kind, whether express or implied; without even the implied warranty
+* of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+* GNU General Public License for more details.
+*/
+/*
+ * DESCRIPTION: The Broadcom iProc RNG200 Driver
+ */
+
+#include <linux/hw_random.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/of_platform.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_RBGEN_DISABLE 0x00000000
+
+#define RNG_SOFT_RESET_OFFSET 0x04
+#define RNG_SOFT_RESET_RNG_SOFT_RESET_MASK 0x00000001
+#define RNG_SOFT_RESET_RNG_SOFT_RESET_ACTIVE 0x00000001
+#define RNG_SOFT_RESET_RNG_SOFT_RESET_CLEAR 0x00000000
+
+#define RBG_SOFT_RESET_OFFSET 0x08
+#define RBG_SOFT_RESET_RNG_SOFT_RESET_MASK 0x00000001
+#define RBG_SOFT_RESET_RNG_SOFT_RESET_ACTIVE 0x00000001
+#define RBG_SOFT_RESET_RNG_SOFT_RESET_CLEAR 0x00000000
+
+#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_FIFO_DATA_OFFSET 0x20
+
+#define RNG_FIFO_COUNT_OFFSET 0x24
+#define RNG_FIFO_COUNT_RNG_FIFO_COUNT_MASK 0x000000FF
+
+static void iproc_rng200_restart(void __iomem *rng_base)
+{
+ uint32_t val;
+
+ /* Disable RBG */
+ val = ioread32(rng_base + RNG_CTRL_OFFSET);
+ val &= ~RNG_CTRL_RNG_RBGEN_MASK;
+ val |= RNG_CTRL_RNG_RBGEN_DISABLE;
+ iowrite32(val, rng_base + RNG_CTRL_OFFSET);
+
+ /* Clear all interrupt status */
+ iowrite32(0xFFFFFFFFUL, rng_base + RNG_INT_STATUS_OFFSET);
+
+ /* Reset RNG and RBG */
+ val = ioread32(rng_base + RBG_SOFT_RESET_OFFSET);
+ val &= ~RBG_SOFT_RESET_RNG_SOFT_RESET_MASK;
+ val |= RBG_SOFT_RESET_RNG_SOFT_RESET_ACTIVE;
+ iowrite32(val, rng_base + RBG_SOFT_RESET_OFFSET);
+
+ val = ioread32(rng_base + RNG_SOFT_RESET_OFFSET);
+ val &= ~RNG_SOFT_RESET_RNG_SOFT_RESET_MASK;
+ val |= RNG_SOFT_RESET_RNG_SOFT_RESET_ACTIVE;
+ iowrite32(val, rng_base + RNG_SOFT_RESET_OFFSET);
+
+ val = ioread32(rng_base + RNG_SOFT_RESET_OFFSET);
+ val &= ~RNG_SOFT_RESET_RNG_SOFT_RESET_MASK;
+ val |= RNG_SOFT_RESET_RNG_SOFT_RESET_CLEAR;
+ iowrite32(val, rng_base + RNG_SOFT_RESET_OFFSET);
+
+ val = ioread32(rng_base + RBG_SOFT_RESET_OFFSET);
+ val &= ~RBG_SOFT_RESET_RNG_SOFT_RESET_MASK;
+ val |= RBG_SOFT_RESET_RNG_SOFT_RESET_CLEAR;
+ iowrite32(val, rng_base + RBG_SOFT_RESET_OFFSET);
+
+ /* Enable RBG */
+ val = ioread32(rng_base + RNG_CTRL_OFFSET);
+ val &= ~RNG_CTRL_RNG_RBGEN_MASK;
+ val |= RNG_CTRL_RNG_RBGEN_ENABLE;
+ iowrite32(val, rng_base + RNG_CTRL_OFFSET);
+}
+
+static int iproc_rng200_read(struct hwrng *rng, void *buf, size_t max,
+ bool wait)
+{
+ uint32_t status = 0;
+ uint32_t num_remaining = max;
+
+ #define MAX_RESETS_PER_READ 1
+ uint32_t num_resets = 0;
+
+ #define MAX_IDLE_TIME (1 * HZ)
+ unsigned long idle_endtime = jiffies + MAX_IDLE_TIME;
+
+ /* Retrieve HW RNG registers base address. */
+ void __iomem *rng_base = (void __iomem *)rng->priv;
+
+ while ((num_remaining > 0) && time_before(jiffies, idle_endtime)) {
+
+ /* Is RNG sane? If not, reset it. */
+ status = ioread32(rng_base + RNG_INT_STATUS_OFFSET);
+ if ((status & (RNG_INT_STATUS_MASTER_FAIL_LOCKOUT_IRQ_MASK |
+ RNG_INT_STATUS_NIST_FAIL_IRQ_MASK)) != 0) {
+
+ if (num_resets >= MAX_RESETS_PER_READ)
+ return max - num_remaining;
+
+ iproc_rng200_restart(rng_base);
+ num_resets++;
+ }
+
+ /* Are there any random numbers available? */
+ if ((ioread32(rng_base + RNG_FIFO_COUNT_OFFSET) &
+ RNG_FIFO_COUNT_RNG_FIFO_COUNT_MASK) > 0) {
+
+ if (num_remaining >= sizeof(uint32_t)) {
+ /* Buffer has room to store entire word */
+ *(uint32_t *)buf = ioread32(rng_base +
+ RNG_FIFO_DATA_OFFSET);
+ buf += sizeof(uint32_t);
+ num_remaining -= sizeof(uint32_t);
+ } else {
+ /* Buffer can only store partial word */
+ uint32_t rnd_number = ioread32(rng_base +
+ RNG_FIFO_DATA_OFFSET);
+ memcpy(buf, &rnd_number, num_remaining);
+ buf += num_remaining;
+ num_remaining = 0;
+ }
+
+ /* Reset the IDLE timeout */
+ idle_endtime = jiffies + MAX_IDLE_TIME;
+ } else {
+ if (!wait)
+ /* Cannot wait, return immediately */
+ return max - num_remaining;
+
+ /* Can wait, give others chance to run */
+ cpu_relax();
+ }
+ }
+
+ return max - num_remaining;
+}
+
+static struct hwrng iproc_rng200_ops = {
+ .name = "iproc-rng200",
+ .read = iproc_rng200_read,
+};

I would prefer if we allocated a driver-private structure that wraps
hwrng instead of using statically allocated singleton as I wonder how it
will behave if I bind/unbind the device several times.
ok, will revamp.

+
+static int iproc_rng200_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ void __iomem *rng_base = 0;
+ uint32_t val = 0;
+ int err = 0;

There is no need to initialize all variables as it suppressed "used but
uninitialized" warnings from the compiler. Imagine someone adding a new
init operation and when they handle failure they forget to adjust error
code so it stays 0: for upper layers we'd signal success even though
our device/driver are half-bound.
yes, will cleanup in other functions as well.

+
+ /* Map peripheral */
+ struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+
+ if (!res) {
+ dev_err(dev, "failed to get rng resources\n");
+ return -ENODEV;

If we have platform device but it is missing parts of necessary data it
should be -EINVAL.
ok

+ }
+
+ rng_base = devm_ioremap_resource(dev, res);
+ if (!rng_base) {

devm_ioremap_resource() returns ERR_PTR-encoded result, you need to
check with IS_ERR().
ok

+ dev_err(dev, "failed to remap rng regs\n");
+ return -ENODEV;

return PTR_ERR(rng_base);
ok

+ }

There is no clock for RNG?
no additional clock needs to be enabled.

+
+ iproc_rng200_ops.priv = (unsigned long)rng_base;
+
+ /* Setup RNG. */
+ val = ioread32(rng_base + RNG_CTRL_OFFSET);
+ val &= ~RNG_CTRL_RNG_RBGEN_MASK;
+ val |= RNG_CTRL_RNG_RBGEN_ENABLE;
+ iowrite32(val, rng_base + RNG_CTRL_OFFSET);

That should be in [new] iproc_rng200_init().
ok, it looks like you are commenting based on what is done in omap-rng. I can follow that model and move this into an init function.

+
+ /* Register driver */
+ err = hwrng_register(&iproc_rng200_ops);
+ if (err) {
+ dev_err(dev, "hwrng registration failed\n");
+ return err;
+ }
+ dev_info(dev, "hwrng registered\n");
+
+ return 0;
+}
+
+static int iproc_rng200_remove(struct platform_device *pdev)
+{
+ uint32_t val = 0;
+ void __iomem *rng_base = (void __iomem *)iproc_rng200_ops.priv;
+
+ /* Unregister driver */
+ hwrng_unregister(&iproc_rng200_ops);
+
+ /* Disable RNG hardware */
+ val = ioread32(rng_base + RNG_CTRL_OFFSET);
+ val &= ~RNG_CTRL_RNG_RBGEN_MASK;
+ val |= RNG_CTRL_RNG_RBGEN_DISABLE;
+ iowrite32(val, rng_base + RNG_CTRL_OFFSET);

That should be in [new] iproc_rng200_cleanup().
ok, it looks like you are commenting based on what is done in omap-rng.

I can follow that model and move this into a cleanup function.

+
+ return 0;
+}
+

#ifdef CONFIG_OF

maybe?
driver will only be used with devicetree

+static const struct of_device_id iproc_rng200_of_match[] = {
+ { .compatible = "brcm,iproc-rng200", },
+ {},
+};
+MODULE_DEVICE_TABLE(of, iproc_rng200_of_match);
+
+static struct platform_driver iproc_rng200_driver = {
+ .driver = {
+ .name = "iproc-rng200",
+ .of_match_table = iproc_rng200_of_match,
+ },
+ .probe = iproc_rng200_probe,
+ .remove = iproc_rng200_remove,
+};
+module_platform_driver(iproc_rng200_driver);
+
+MODULE_AUTHOR("Broadcom");
+MODULE_DESCRIPTION("iProc RNG200 Random Number Generator driver");
+MODULE_LICENSE("GPL v2");
--
2.3.0


Thanks.


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