[2/3] hwrng: Add a driver for the hwrng found in power7+ systems

Commit Message

Michael Ellerman Sept. 26, 2013, 6:31 a.m. UTC

Add a driver for the hwrng found in power7+ systems, based on the
existing code for the arch_get_random_long() hook.

We only register a single instance of the driver, not one per device,
because we use the existing per_cpu array of devices in the arch code.
This means we always read from the "closest" device, avoiding inter-chip
memory traffic.

Signed-off-by: Guo Chao <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>
---
 drivers/char/hw_random/Kconfig       | 13 ++++++
 drivers/char/hw_random/Makefile      |  1 +
 drivers/char/hw_random/powernv-rng.c | 81 ++++++++++++++++++++++++++++++++++++
 3 files changed, 95 insertions(+)
 create mode 100644 drivers/char/hw_random/powernv-rng.c

Comments

Benjamin Herrenschmidt Sept. 26, 2013, 8:01 a.m. UTC | #1

On Thu, 2013-09-26 at 16:31 +1000, Michael Ellerman wrote:

> +       pr_info("registered powernv hwrng.\n");

First letter of a line should get a capital :-) Also since
it's per-device, at least indicate the OF path or the chip number or
something ...

Cheers,
Ben.



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Michael Ellerman Oct. 1, 2013, 8:25 a.m. UTC | #2

On Thu, Sep 26, 2013 at 06:01:27PM +1000, Benjamin Herrenschmidt wrote:
> On Thu, 2013-09-26 at 16:31 +1000, Michael Ellerman wrote:
> 
> > +       pr_info("registered powernv hwrng.\n");
> 
> First letter of a line should get a capital :-) Also since
> it's per-device, at least indicate the OF path or the chip number or
> something ...

It's not the first letter, it looks like this:

  powernv-rng: registered powernv hwrng.

Which looks nice to me, but I can make it this if you prefer:

  powernv-rng: Registered powernv hwrng.


And it's not per-device due to the trick in the probe routine. It's a
bit sneaky but we need to make it a proper driver for module loading to
work, but we only want to register one hwrng device.

cheers
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Patch

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index 0aa9d91..c206de2 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -290,6 +290,19 @@  config HW_RANDOM_PSERIES
 
 	  If unsure, say Y.
 
+config HW_RANDOM_POWERNV
+	tristate "PowerNV Random Number Generator support"
+	depends on HW_RANDOM && PPC_POWERNV
+	default HW_RANDOM
+	---help---
+	  This is the driver for Random Number Generator hardware found
+	  in POWER7+ and above machines for PowerNV platform.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called powernv-rng.
+
+	  If unsure, say Y.
+
 config HW_RANDOM_EXYNOS
 	tristate "EXYNOS HW random number generator support"
 	depends on HW_RANDOM && HAS_IOMEM && HAVE_CLK
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index bed467c..d7d2435 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -24,6 +24,7 @@  obj-$(CONFIG_HW_RANDOM_NOMADIK) += nomadik-rng.o
 obj-$(CONFIG_HW_RANDOM_PICOXCELL) += picoxcell-rng.o
 obj-$(CONFIG_HW_RANDOM_PPC4XX) += ppc4xx-rng.o
 obj-$(CONFIG_HW_RANDOM_PSERIES) += pseries-rng.o
+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
diff --git a/drivers/char/hw_random/powernv-rng.c b/drivers/char/hw_random/powernv-rng.c
new file mode 100644
index 0000000..e6965bf
--- /dev/null
+++ b/drivers/char/hw_random/powernv-rng.c
@@ -0,0 +1,81 @@ 
+/*
+ * Copyright 2013 Michael Ellerman, Guo Chao, IBM Corp.
+ *
+ * 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; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+#include <linux/random.h>
+#include <linux/hw_random.h>
+
+static int powernv_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
+{
+	unsigned long *buf;
+	int i, len;
+
+	/* We rely on rng_buffer_size() being >= sizeof(unsigned long) */
+	len = max / sizeof(unsigned long);
+
+	buf = (unsigned long *)data;
+
+	for (i = 0; i < len; i++)
+		powernv_get_random_long(buf++);
+
+	return len * sizeof(unsigned long);
+}
+
+static struct hwrng powernv_hwrng = {
+	.name = "powernv-rng",
+	.read = powernv_rng_read,
+};
+
+static int powernv_rng_remove(struct platform_device *pdev)
+{
+	hwrng_unregister(&powernv_hwrng);
+
+	return 0;
+}
+
+static int powernv_rng_probe(struct platform_device *pdev)
+{
+	int rc;
+
+	rc = hwrng_register(&powernv_hwrng);
+	if (rc) {
+		/* We only register one device, ignore any others */
+		if (rc == -EEXIST)
+			rc = -ENODEV;
+
+		return rc;
+	}
+
+	pr_info("registered powernv hwrng.\n");
+
+	return 0;
+}
+
+static struct of_device_id powernv_rng_match[] = {
+	{ .compatible	= "ibm,power-rng",},
+	{},
+};
+MODULE_DEVICE_TABLE(of, powernv_rng_match);
+
+static struct platform_driver powernv_rng_driver = {
+	.driver = {
+		.name = "powernv_rng",
+		.of_match_table = powernv_rng_match,
+	},
+	.probe	= powernv_rng_probe,
+	.remove = powernv_rng_remove,
+};
+module_platform_driver(powernv_rng_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Bare metal HWRNG driver for POWER7+ and above");