[PATCH 0/3] crypto: hw_random - Add new Exynos RNG driver

[PATCH 0/3] crypto: hw_random - Add new Exynos RNG driver

[Krzysztof Kozlowski]

Hi,

This is a follow up of my questions around exynos-rng [1].

The existing exynos-rng has many issues.  The most important one is that
it is a pseudo RNG device but uses hw_random interface which does not allow
proper seeding.

The RNG module on Exynos4 requires seeding.  On newer SoCs (like Exynos5420)
it can seed itself from a true RNG.  Converting the existing driver
to use TRNG would effectively drop support for Exynos4 and break
compatibility with existing users.

Instead I decided to convert it to crypto API.  In the future I hope
to add support for seeding from TRNG module.

Tested with app [2].

Patches are independent. I will take the defconfig changes (2/3 and 3/3)
through samsung-soc tree.

Best regards,
Krzysztof

[1] https://www.spinics.net/lists/arm-kernel/msg569641.html
[2] https://www.spinics.net/lists/arm-kernel/msg571184.html

Krzysztof Kozlowski (3):
  crypto: hw_random - Add new Exynos RNG driver
  ARM: exynos_defconfig: Enable Exynos RNG and user-space crypto API
  ARM: multi_v7_defconfig: Enable Exynos RNG and user-space crypto API

 MAINTAINERS                         |   8 +
 arch/arm/configs/exynos_defconfig   |   6 +
 arch/arm/configs/multi_v7_defconfig |   6 +
 drivers/char/hw_random/Kconfig      |  14 --
 drivers/char/hw_random/Makefile     |   1 -
 drivers/char/hw_random/exynos-rng.c | 231 ---------------------------
 drivers/crypto/Kconfig              |  15 ++
 drivers/crypto/Makefile             |   1 +
 drivers/crypto/exynos-rng.c         | 306 ++++++++++++++++++++++++++++++++++++
 9 files changed, 342 insertions(+), 246 deletions(-)
 delete mode 100644 drivers/char/hw_random/exynos-rng.c
 create mode 100644 drivers/crypto/exynos-rng.c

-- 
2.9.3

[PATCH 1/3] crypto: hw_random - Add new Exynos RNG driver

[Krzysztof Kozlowski]

Replace existing hw_ranndom/exynos-rng driver with a new, reworked one.
This is a driver for pseudo random number generator block which on
Exynos4 chipsets must be seeded with some value.  On newer Exynos5420
chipsets it might seed itself from true random number generator block
but this is not implemented yet.

New driver is a complete rework to use the crypto ALGAPI instead of
hw_random API.  Rationale for the change:
1. hw_random interface is for true RNG devices.
2. The old driver was seeding itself with jiffies which is not a
   reliable source for randomness.
3. Device generates five random numbers in each pass but old driver was
   returning only one thus its performance was reduced.

Compatibility with DeviceTree bindings is preserved.

New driver does not use runtime power management but manually enables
and disables the clock when needed.  This is preferred approach because
using runtime PM just to toggle clock is huge overhead.  Another
difference is using the same seed after resuming from system suspend
(previously driver was re-seeding itself again with jiffies).

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
---
 MAINTAINERS                         |   8 +
 drivers/char/hw_random/Kconfig      |  14 --
 drivers/char/hw_random/Makefile     |   1 -
 drivers/char/hw_random/exynos-rng.c | 231 ---------------------------
 drivers/crypto/Kconfig              |  15 ++
 drivers/crypto/Makefile             |   1 +
 drivers/crypto/exynos-rng.c         | 306 ++++++++++++++++++++++++++++++++++++
 7 files changed, 330 insertions(+), 246 deletions(-)
 delete mode 100644 drivers/char/hw_random/exynos-rng.c
 create mode 100644 drivers/crypto/exynos-rng.c

diff --git a/MAINTAINERS b/MAINTAINERS
index affecc6d59f4..371fda859d43 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10977,6 +10977,14 @@ L:	alsa-devel at alsa-project.org (moderated for non-subscribers)
 S:	Supported
 F:	sound/soc/samsung/
 
+SAMSUNG EXYNOS PSEUDO RANDOM NUMBER GENERATOR (RNG) DRIVER
+M:	Krzysztof Kozlowski <krzk@kernel.org>
+L:	linux-crypto at vger.kernel.org
+L:	linux-samsung-soc at vger.kernel.org
+S:	Maintained
+F:	drivers/crypto/exynos-rng.c
+F:	Documentation/devicetree/bindings/rng/samsung,exynos-rng4.txt
+
 SAMSUNG FRAMEBUFFER DRIVER
 M:	Jingoo Han <jingoohan1@gmail.com>
 L:	linux-fbdev at vger.kernel.org
diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index 0cafe08919c9..bdae802e7154 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -294,20 +294,6 @@ config HW_RANDOM_POWERNV
 
 	  If unsure, say Y.
 
-config HW_RANDOM_EXYNOS
-	tristate "EXYNOS HW random number generator support"
-	depends on ARCH_EXYNOS || COMPILE_TEST
-	depends on HAS_IOMEM
-	default HW_RANDOM
-	---help---
-	  This driver provides kernel-side support for the Random Number
-	  Generator hardware found on EXYNOS SOCs.
-
-	  To compile this driver as a module, choose M here: the
-	  module will be called exynos-rng.
-
-	  If unsure, say Y.
-
 config HW_RANDOM_TPM
 	tristate "TPM HW Random Number Generator support"
 	depends on TCG_TPM
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index 5f52b1e4e7be..6f1eecc2045c 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -24,7 +24,6 @@ obj-$(CONFIG_HW_RANDOM_OCTEON) += octeon-rng.o
 obj-$(CONFIG_HW_RANDOM_NOMADIK) += nomadik-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_HISI)	+= hisi-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/exynos-rng.c b/drivers/char/hw_random/exynos-rng.c
deleted file mode 100644
index 23d358553b21..000000000000
--- a/drivers/char/hw_random/exynos-rng.c
+++ /dev/null
@@ -1,231 +0,0 @@
-/*
- * exynos-rng.c - Random Number Generator driver for the exynos
- *
- * Copyright (C) 2012 Samsung Electronics
- * Jonghwa Lee <jonghwa3.lee@samsung.com>
- *
- * 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;
- *
- * 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.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
- *
- */
-
-#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>
-
-#define EXYNOS_PRNG_STATUS_OFFSET	0x10
-#define EXYNOS_PRNG_SEED_OFFSET		0x140
-#define EXYNOS_PRNG_OUT1_OFFSET		0x160
-#define SEED_SETTING_DONE		BIT(1)
-#define PRNG_START			0x18
-#define PRNG_DONE			BIT(5)
-#define EXYNOS_AUTOSUSPEND_DELAY	100
-
-struct exynos_rng {
-	struct device *dev;
-	struct hwrng rng;
-	void __iomem *mem;
-	struct clk *clk;
-};
-
-static u32 exynos_rng_readl(struct exynos_rng *rng, u32 offset)
-{
-	return	readl_relaxed(rng->mem + offset);
-}
-
-static void exynos_rng_writel(struct exynos_rng *rng, u32 val, u32 offset)
-{
-	writel_relaxed(val, rng->mem + offset);
-}
-
-static int exynos_rng_configure(struct exynos_rng *exynos_rng)
-{
-	int i;
-	int ret = 0;
-
-	for (i = 0 ; i < 5 ; i++)
-		exynos_rng_writel(exynos_rng, jiffies,
-				EXYNOS_PRNG_SEED_OFFSET + 4*i);
-
-	if (!(exynos_rng_readl(exynos_rng, EXYNOS_PRNG_STATUS_OFFSET)
-						 & SEED_SETTING_DONE))
-		ret = -EIO;
-
-	return ret;
-}
-
-static int exynos_init(struct hwrng *rng)
-{
-	struct exynos_rng *exynos_rng = container_of(rng,
-						struct exynos_rng, rng);
-	int ret = 0;
-
-	pm_runtime_get_sync(exynos_rng->dev);
-	ret = exynos_rng_configure(exynos_rng);
-	pm_runtime_mark_last_busy(exynos_rng->dev);
-	pm_runtime_put_autosuspend(exynos_rng->dev);
-
-	return ret;
-}
-
-static int exynos_read(struct hwrng *rng, void *buf,
-					size_t max, bool wait)
-{
-	struct exynos_rng *exynos_rng = container_of(rng,
-						struct exynos_rng, rng);
-	u32 *data = buf;
-	int retry = 100;
-	int ret = 4;
-
-	pm_runtime_get_sync(exynos_rng->dev);
-
-	exynos_rng_writel(exynos_rng, PRNG_START, 0);
-
-	while (!(exynos_rng_readl(exynos_rng,
-			EXYNOS_PRNG_STATUS_OFFSET) & PRNG_DONE) && --retry)
-		cpu_relax();
-	if (!retry) {
-		ret = -ETIMEDOUT;
-		goto out;
-	}
-
-	exynos_rng_writel(exynos_rng, PRNG_DONE, EXYNOS_PRNG_STATUS_OFFSET);
-
-	*data = exynos_rng_readl(exynos_rng, EXYNOS_PRNG_OUT1_OFFSET);
-
-out:
-	pm_runtime_mark_last_busy(exynos_rng->dev);
-	pm_runtime_put_sync_autosuspend(exynos_rng->dev);
-
-	return ret;
-}
-
-static int exynos_rng_probe(struct platform_device *pdev)
-{
-	struct exynos_rng *exynos_rng;
-	struct resource *res;
-	int ret;
-
-	exynos_rng = devm_kzalloc(&pdev->dev, sizeof(struct exynos_rng),
-					GFP_KERNEL);
-	if (!exynos_rng)
-		return -ENOMEM;
-
-	exynos_rng->dev = &pdev->dev;
-	exynos_rng->rng.name = "exynos";
-	exynos_rng->rng.init =	exynos_init;
-	exynos_rng->rng.read = exynos_read;
-	exynos_rng->clk = devm_clk_get(&pdev->dev, "secss");
-	if (IS_ERR(exynos_rng->clk)) {
-		dev_err(&pdev->dev, "Couldn't get clock.\n");
-		return -ENOENT;
-	}
-
-	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-	exynos_rng->mem = devm_ioremap_resource(&pdev->dev, res);
-	if (IS_ERR(exynos_rng->mem))
-		return PTR_ERR(exynos_rng->mem);
-
-	platform_set_drvdata(pdev, exynos_rng);
-
-	pm_runtime_set_autosuspend_delay(&pdev->dev, EXYNOS_AUTOSUSPEND_DELAY);
-	pm_runtime_use_autosuspend(&pdev->dev);
-	pm_runtime_enable(&pdev->dev);
-
-	ret = devm_hwrng_register(&pdev->dev, &exynos_rng->rng);
-	if (ret) {
-		pm_runtime_dont_use_autosuspend(&pdev->dev);
-		pm_runtime_disable(&pdev->dev);
-	}
-
-	return ret;
-}
-
-static int exynos_rng_remove(struct platform_device *pdev)
-{
-	pm_runtime_dont_use_autosuspend(&pdev->dev);
-	pm_runtime_disable(&pdev->dev);
-
-	return 0;
-}
-
-static int __maybe_unused exynos_rng_runtime_suspend(struct device *dev)
-{
-	struct platform_device *pdev = to_platform_device(dev);
-	struct exynos_rng *exynos_rng = platform_get_drvdata(pdev);
-
-	clk_disable_unprepare(exynos_rng->clk);
-
-	return 0;
-}
-
-static int __maybe_unused exynos_rng_runtime_resume(struct device *dev)
-{
-	struct platform_device *pdev = to_platform_device(dev);
-	struct exynos_rng *exynos_rng = platform_get_drvdata(pdev);
-
-	return clk_prepare_enable(exynos_rng->clk);
-}
-
-static int __maybe_unused exynos_rng_suspend(struct device *dev)
-{
-	return pm_runtime_force_suspend(dev);
-}
-
-static int __maybe_unused exynos_rng_resume(struct device *dev)
-{
-	struct platform_device *pdev = to_platform_device(dev);
-	struct exynos_rng *exynos_rng = platform_get_drvdata(pdev);
-	int ret;
-
-	ret = pm_runtime_force_resume(dev);
-	if (ret)
-		return ret;
-
-	return exynos_rng_configure(exynos_rng);
-}
-
-static const struct dev_pm_ops exynos_rng_pm_ops = {
-	SET_SYSTEM_SLEEP_PM_OPS(exynos_rng_suspend, exynos_rng_resume)
-	SET_RUNTIME_PM_OPS(exynos_rng_runtime_suspend,
-			   exynos_rng_runtime_resume, NULL)
-};
-
-static const struct of_device_id exynos_rng_dt_match[] = {
-	{
-		.compatible = "samsung,exynos4-rng",
-	},
-	{ },
-};
-MODULE_DEVICE_TABLE(of, exynos_rng_dt_match);
-
-static struct platform_driver exynos_rng_driver = {
-	.driver		= {
-		.name	= "exynos-rng",
-		.pm	= &exynos_rng_pm_ops,
-		.of_match_table = exynos_rng_dt_match,
-	},
-	.probe		= exynos_rng_probe,
-	.remove		= exynos_rng_remove,
-};
-
-module_platform_driver(exynos_rng_driver);
-
-MODULE_DESCRIPTION("EXYNOS 4 H/W Random Number Generator driver");
-MODULE_AUTHOR("Jonghwa Lee <jonghwa3.lee@samsung.com>");
-MODULE_LICENSE("GPL");
diff --git a/drivers/crypto/Kconfig b/drivers/crypto/Kconfig
index 1a60626937e4..7d1fdf6a751c 100644
--- a/drivers/crypto/Kconfig
+++ b/drivers/crypto/Kconfig
@@ -388,6 +388,21 @@ config CRYPTO_DEV_MXC_SCC
 	  This option enables support for the Security Controller (SCC)
 	  found in Freescale i.MX25 chips.
 
+config CRYPTO_DEV_EXYNOS_RNG
+	tristate "EXYNOS HW pseudo random number generator support"
+	depends on ARCH_EXYNOS || COMPILE_TEST
+	depends on HAS_IOMEM
+	select CRYPTO_RNG
+	---help---
+	  This driver provides kernel-side support through the
+	  cryptographic API for the pseudo random number generator hardware
+	  found on Exynos SoCs.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called exynos-rng.
+
+	  If unsure, say Y.
+
 config CRYPTO_DEV_S5P
 	tristate "Support for Samsung S5PV210/Exynos crypto accelerator"
 	depends on ARCH_S5PV210 || ARCH_EXYNOS || COMPILE_TEST
diff --git a/drivers/crypto/Makefile b/drivers/crypto/Makefile
index 41ca339e89d3..9603f1862b30 100644
--- a/drivers/crypto/Makefile
+++ b/drivers/crypto/Makefile
@@ -6,6 +6,7 @@ obj-$(CONFIG_CRYPTO_DEV_CAVIUM_ZIP) += cavium/
 obj-$(CONFIG_CRYPTO_DEV_CCP) += ccp/
 obj-$(CONFIG_CRYPTO_DEV_CHELSIO) += chelsio/
 obj-$(CONFIG_CRYPTO_DEV_CPT) += cavium/cpt/
+obj-$(CONFIG_CRYPTO_DEV_EXYNOS_RNG) += exynos-rng.o
 obj-$(CONFIG_CRYPTO_DEV_FSL_CAAM) += caam/
 obj-$(CONFIG_CRYPTO_DEV_GEODE) += geode-aes.o
 obj-$(CONFIG_CRYPTO_DEV_HIFN_795X) += hifn_795x.o
diff --git a/drivers/crypto/exynos-rng.c b/drivers/crypto/exynos-rng.c
new file mode 100644
index 000000000000..9993f0eb3425
--- /dev/null
+++ b/drivers/crypto/exynos-rng.c
@@ -0,0 +1,306 @@
+/*
+ * exynos-rng.c - Random Number Generator driver for the Exynos
+ *
+ * Copyright (c) 2017 Krzysztof Kozlowski <krzk@kernel.org>
+ *
+ * Loosely based on old driver from drivers/char/hw_random/exynos-rng.c:
+ * Copyright (C) 2012 Samsung Electronics
+ * Jonghwa Lee <jonghwa3.lee@samsung.com>
+ *
+ * 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;
+ *
+ * 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/clk.h>
+#include <linux/crypto.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+#include <crypto/internal/rng.h>
+
+#define EXYNOS_RNG_CONTROL		0x0
+#define EXYNOS_RNG_STATUS		0x10
+#define EXYNOS_RNG_SEED_BASE		0x140
+#define EXYNOS_RNG_SEED(n)		(EXYNOS_RNG_SEED_BASE + (n * 0x4))
+#define EXYNOS_RNG_OUT_BASE		0x160
+#define EXYNOS_RNG_OUT(n)		(EXYNOS_RNG_OUT_BASE + (n * 0x4))
+
+/* EXYNOS_RNG_CONTROL bit fields */
+#define EXYNOS_RNG_CONTROL_START	0x18
+/* EXYNOS_RNG_STATUS bit fields */
+#define EXYNOS_RNG_STATUS_SEED_SETTING_DONE	BIT(1)
+#define EXYNOS_RNG_STATUS_RNG_DONE		BIT(5)
+
+/* Five seed and output registers, each 4 bytes */
+#define EXYNOS_RNG_SEED_REGS		5
+#define EXYNOS_RNG_SEED_SIZE		(EXYNOS_RNG_SEED_REGS * 4)
+
+/* Context for crypto */
+struct exynos_rng_ctx {
+	struct exynos_rng_dev		*rng;
+};
+
+/* Device associated memory */
+struct exynos_rng_dev {
+	struct device			*dev;
+	struct exynos_rng_ctx		*ctx;
+	void __iomem			*mem;
+	struct clk			*clk;
+	u8				seed_save[EXYNOS_RNG_SEED_SIZE];
+};
+
+static struct exynos_rng_dev *exynos_rng_dev;
+
+static u32 exynos_rng_readl(struct exynos_rng_dev *rng, u32 offset)
+{
+	return readl_relaxed(rng->mem + offset);
+}
+
+static void exynos_rng_writel(struct exynos_rng_dev *rng, u32 val, u32 offset)
+{
+	writel_relaxed(val, rng->mem + offset);
+}
+
+static unsigned int exynos_rng_copy_random(struct exynos_rng_dev *rng,
+					   u8 *dst, unsigned int dlen)
+{
+	unsigned int cnt = 0;
+	int i, j;
+	u32 val;
+
+	for (j = 0; j < EXYNOS_RNG_SEED_REGS; j++) {
+		val = exynos_rng_readl(rng, EXYNOS_RNG_OUT(j));
+
+		for (i = 0; i < 4; i++) {
+			dst[cnt] = val & 0xff;
+			val >>= 8;
+			if (++cnt >= dlen)
+				return cnt;
+		}
+	}
+
+	return cnt;
+}
+
+static int exynos_rng_get_random(struct exynos_rng_dev *rng,
+				 u8 *dst, unsigned int dlen,
+				 unsigned int *read)
+{
+	int retry = 100;
+
+	exynos_rng_writel(rng, EXYNOS_RNG_CONTROL_START,
+			  EXYNOS_RNG_CONTROL);
+
+	while (!(exynos_rng_readl(rng,
+			EXYNOS_RNG_STATUS) & EXYNOS_RNG_STATUS_RNG_DONE) && --retry)
+		cpu_relax();
+
+	if (!retry)
+		return -ETIMEDOUT;
+
+	/* Clear status bit */
+	exynos_rng_writel(rng, EXYNOS_RNG_STATUS_RNG_DONE,
+			  EXYNOS_RNG_STATUS);
+
+	*read = exynos_rng_copy_random(rng, dst, dlen);
+
+	return 0;
+}
+
+static int exynos_rng_generate(struct crypto_rng *tfm,
+			       const u8 *src, unsigned int slen,
+			       u8 *dst, unsigned int dlen)
+{
+	struct exynos_rng_ctx *ctx = crypto_rng_ctx(tfm);
+	struct exynos_rng_dev *rng = ctx->rng;
+	unsigned int read = 0;
+	int ret;
+
+	ret = clk_prepare_enable(rng->clk);
+	if (ret)
+		return ret;
+
+	do {
+		ret = exynos_rng_get_random(rng, dst, dlen, &read);
+		if (ret)
+			break;
+
+		dlen -= read;
+		dst += read;
+	} while (dlen > 0);
+
+	clk_disable_unprepare(rng->clk);
+
+	return ret;
+}
+
+static int exynos_rng_set_seed(struct exynos_rng_dev *rng,
+			       const u8 *seed, unsigned int slen)
+{
+	int ret, i;
+	u32 val;
+
+	dev_dbg(rng->dev, "Seeding with %u bytes\n", slen);
+
+	ret = clk_prepare_enable(rng->clk);
+	if (ret)
+		return ret;
+
+	if (slen < EXYNOS_RNG_SEED_SIZE) {
+		dev_warn(rng->dev, "Seed too short (only %u bytes)\n", slen);
+		ret = -EINVAL;
+		goto out;
+	}
+
+	for (i = 0 ; i < EXYNOS_RNG_SEED_REGS ; i++) {
+		val = seed[i * 4] << 24;
+		val |= seed[i * 4 + 1] << 16;
+		val |= seed[i * 4 + 2] << 8;
+		val |= seed[i * 4 + 3] << 0;
+
+		exynos_rng_writel(rng, val, EXYNOS_RNG_SEED(i));
+	}
+
+	val = exynos_rng_readl(rng, EXYNOS_RNG_STATUS);
+	if (!(val & EXYNOS_RNG_STATUS_SEED_SETTING_DONE)) {
+		dev_warn(rng->dev, "Seed setting not finished\n");
+		ret = -EIO;
+		goto out;
+	}
+
+	ret = 0;
+	/* Save seed for suspend */
+	memcpy(rng->seed_save, seed, slen);
+
+out:
+	clk_disable_unprepare(rng->clk);
+
+	return ret;
+}
+
+static int exynos_rng_seed(struct crypto_rng *tfm, const u8 *seed,
+			   unsigned int slen)
+{
+	struct exynos_rng_ctx *ctx = crypto_rng_ctx(tfm);
+
+	return exynos_rng_set_seed(ctx->rng, seed, slen);
+}
+
+static int exynos_rng_kcapi_init(struct crypto_tfm *tfm)
+{
+	struct exynos_rng_ctx *ctx = crypto_tfm_ctx(tfm);
+
+	ctx->rng = exynos_rng_dev;
+
+	return 0;
+}
+
+static struct rng_alg exynos_rng_alg = {
+	.generate		= exynos_rng_generate,
+	.seed			= exynos_rng_seed,
+	.seedsize		= EXYNOS_RNG_SEED_SIZE,
+	.base			= {
+		.cra_name		= "exynos_rng",
+		.cra_driver_name	= "exynos_rng",
+		.cra_priority		= 100,
+		.cra_ctxsize		= sizeof(struct exynos_rng_ctx),
+		.cra_module		= THIS_MODULE,
+		.cra_init		= exynos_rng_kcapi_init,
+	}
+};
+
+static int exynos_rng_probe(struct platform_device *pdev)
+{
+	struct exynos_rng_dev *rng;
+	struct resource *res;
+	int ret;
+
+	if (exynos_rng_dev)
+		return -EEXIST;
+
+	rng = devm_kzalloc(&pdev->dev, sizeof(*rng), GFP_KERNEL);
+	if (!rng)
+		return -ENOMEM;
+
+	rng->dev = &pdev->dev;
+	rng->clk = devm_clk_get(&pdev->dev, "secss");
+	if (IS_ERR(rng->clk)) {
+		dev_err(&pdev->dev, "Couldn't get clock.\n");
+		return PTR_ERR(rng->clk);
+	}
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	rng->mem = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(rng->mem))
+		return PTR_ERR(rng->mem);
+
+	platform_set_drvdata(pdev, rng);
+
+	exynos_rng_dev = rng;
+
+	ret = crypto_register_rng(&exynos_rng_alg);
+	if (ret) {
+		dev_err(&pdev->dev,
+			"Couldn't register rng crypto alg: %d\n", ret);
+		exynos_rng_dev = NULL;
+	}
+
+	return ret;
+}
+
+static int exynos_rng_remove(struct platform_device *pdev)
+{
+	crypto_unregister_rng(&exynos_rng_alg);
+
+	exynos_rng_dev = NULL;
+
+	return 0;
+}
+
+static int __maybe_unused exynos_rng_suspend(struct device *dev)
+{
+	return 0;
+}
+
+static int __maybe_unused exynos_rng_resume(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct exynos_rng_dev *rng = platform_get_drvdata(pdev);
+
+	return exynos_rng_set_seed(rng, rng->seed_save, sizeof(rng->seed_save));
+}
+
+static SIMPLE_DEV_PM_OPS(exynos_rng_pm_ops, exynos_rng_suspend,
+			 exynos_rng_resume);
+
+static const struct of_device_id exynos_rng_dt_match[] = {
+	{
+		.compatible = "samsung,exynos4-rng",
+	},
+	{ },
+};
+MODULE_DEVICE_TABLE(of, exynos_rng_dt_match);
+
+static struct platform_driver exynos_rng_driver = {
+	.driver		= {
+		.name	= "exynos-rng",
+		.pm	= &exynos_rng_pm_ops,
+		.of_match_table = exynos_rng_dt_match,
+	},
+	.probe		= exynos_rng_probe,
+	.remove		= exynos_rng_remove,
+};
+
+module_platform_driver(exynos_rng_driver);
+
+MODULE_DESCRIPTION("Exynos H/W Random Number Generator driver");
+MODULE_AUTHOR("Krzysztof Kozlowski <krzk@kernel.org>");
+MODULE_LICENSE("GPL");
-- 
2.9.3

[PATCH 1/3] crypto: hw_random - Add new Exynos RNG driver

[Stephan Müller]

Am Freitag, 24. M?rz 2017, 15:24:44 CET schrieb Krzysztof Kozlowski:

Hi Krzysztof,

> +
> +static int exynos_rng_set_seed(struct exynos_rng_dev *rng,
> +			       const u8 *seed, unsigned int slen)
> +{
> +	int ret, i;
> +	u32 val;
> +
> +	dev_dbg(rng->dev, "Seeding with %u bytes\n", slen);
> +
> +	ret = clk_prepare_enable(rng->clk);
> +	if (ret)
> +		return ret;
> +
> +	if (slen < EXYNOS_RNG_SEED_SIZE) {
> +		dev_warn(rng->dev, "Seed too short (only %u bytes)\n", slen);
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	for (i = 0 ; i < EXYNOS_RNG_SEED_REGS ; i++) {
> +		val = seed[i * 4] << 24;
> +		val |= seed[i * 4 + 1] << 16;
> +		val |= seed[i * 4 + 2] << 8;
> +		val |= seed[i * 4 + 3] << 0;
> +
> +		exynos_rng_writel(rng, val, EXYNOS_RNG_SEED(i));
> +	}
> +
> +	val = exynos_rng_readl(rng, EXYNOS_RNG_STATUS);
> +	if (!(val & EXYNOS_RNG_STATUS_SEED_SETTING_DONE)) {
> +		dev_warn(rng->dev, "Seed setting not finished\n");
> +		ret = -EIO;
> +		goto out;
> +	}
> +
> +	ret = 0;
> +	/* Save seed for suspend */
> +	memcpy(rng->seed_save, seed, slen);

Is this really necessary? If you need to save some seed, shouldn't that be an 
output of the DRNG and not the real seed?

Besides, how do you know that slen is not larger than EXYNOS_RNG_SEED_SIZE?


Ciao
Stephan

[PATCH 1/3] crypto: hw_random - Add new Exynos RNG driver

[Krzysztof Kozlowski]

On Fri, Mar 24, 2017 at 03:37:59PM +0100, Stephan M?ller wrote:
> Am Freitag, 24. M?rz 2017, 15:24:44 CET schrieb Krzysztof Kozlowski:
> 
> Hi Krzysztof,
> 
> > +
> > +static int exynos_rng_set_seed(struct exynos_rng_dev *rng,
> > +			       const u8 *seed, unsigned int slen)
> > +{
> > +	int ret, i;
> > +	u32 val;
> > +
> > +	dev_dbg(rng->dev, "Seeding with %u bytes\n", slen);
> > +
> > +	ret = clk_prepare_enable(rng->clk);
> > +	if (ret)
> > +		return ret;
> > +
> > +	if (slen < EXYNOS_RNG_SEED_SIZE) {
> > +		dev_warn(rng->dev, "Seed too short (only %u bytes)\n", slen);
> > +		ret = -EINVAL;
> > +		goto out;
> > +	}
> > +
> > +	for (i = 0 ; i < EXYNOS_RNG_SEED_REGS ; i++) {
> > +		val = seed[i * 4] << 24;
> > +		val |= seed[i * 4 + 1] << 16;
> > +		val |= seed[i * 4 + 2] << 8;
> > +		val |= seed[i * 4 + 3] << 0;
> > +
> > +		exynos_rng_writel(rng, val, EXYNOS_RNG_SEED(i));
> > +	}
> > +
> > +	val = exynos_rng_readl(rng, EXYNOS_RNG_STATUS);
> > +	if (!(val & EXYNOS_RNG_STATUS_SEED_SETTING_DONE)) {
> > +		dev_warn(rng->dev, "Seed setting not finished\n");
> > +		ret = -EIO;
> > +		goto out;
> > +	}
> > +
> > +	ret = 0;
> > +	/* Save seed for suspend */
> > +	memcpy(rng->seed_save, seed, slen);
> 
> Is this really necessary? If you need to save some seed, shouldn't that be an 
> output of the DRNG and not the real seed?

When suspended to RAM device will loose the contents of registers
(including SEED registers) so it has to be initialized with something on
resume.

The seed registers are write-only so I cannot read them and store
contents just before suspend.

I understand that real seed should not be stored... but then if I am not
able to re-seed it with same values, I will loose the continuous and
reproducible pseudo-random generation after suspend. Aren't this
expected out of PRNG?

> Besides, how do you know that slen is not larger than EXYNOS_RNG_SEED_SIZE?

Right, there is a overflow here. It should be sizeof(rng->seed_save);

Thanks for review!

Best regards,
Krzysztof

[PATCH 1/3] crypto: hw_random - Add new Exynos RNG driver

[Stephan Müller]

Am Freitag, 24. M?rz 2017, 15:43:48 CET schrieb Krzysztof Kozlowski:

Hi Krzysztof,

> On Fri, Mar 24, 2017 at 03:37:59PM +0100, Stephan M?ller wrote:
> > Am Freitag, 24. M?rz 2017, 15:24:44 CET schrieb Krzysztof Kozlowski:
> > 
> > Hi Krzysztof,
> > 
> > > +
> > > +static int exynos_rng_set_seed(struct exynos_rng_dev *rng,
> > > +			       const u8 *seed, unsigned int slen)
> > > +{
> > > +	int ret, i;
> > > +	u32 val;
> > > +
> > > +	dev_dbg(rng->dev, "Seeding with %u bytes\n", slen);
> > > +
> > > +	ret = clk_prepare_enable(rng->clk);
> > > +	if (ret)
> > > +		return ret;
> > > +
> > > +	if (slen < EXYNOS_RNG_SEED_SIZE) {
> > > +		dev_warn(rng->dev, "Seed too short (only %u bytes)\n", slen);
> > > +		ret = -EINVAL;
> > > +		goto out;
> > > +	}
> > > +
> > > +	for (i = 0 ; i < EXYNOS_RNG_SEED_REGS ; i++) {
> > > +		val = seed[i * 4] << 24;
> > > +		val |= seed[i * 4 + 1] << 16;
> > > +		val |= seed[i * 4 + 2] << 8;
> > > +		val |= seed[i * 4 + 3] << 0;
> > > +
> > > +		exynos_rng_writel(rng, val, EXYNOS_RNG_SEED(i));
> > > +	}
> > > +
> > > +	val = exynos_rng_readl(rng, EXYNOS_RNG_STATUS);
> > > +	if (!(val & EXYNOS_RNG_STATUS_SEED_SETTING_DONE)) {
> > > +		dev_warn(rng->dev, "Seed setting not finished\n");
> > > +		ret = -EIO;
> > > +		goto out;
> > > +	}
> > > +
> > > +	ret = 0;
> > > +	/* Save seed for suspend */
> > > +	memcpy(rng->seed_save, seed, slen);
> > 
> > Is this really necessary? If you need to save some seed, shouldn't that be
> > an output of the DRNG and not the real seed?
> 
> When suspended to RAM device will loose the contents of registers
> (including SEED registers) so it has to be initialized with something on
> resume.
> 
> The seed registers are write-only so I cannot read them and store
> contents just before suspend.
> 
> I understand that real seed should not be stored... but then if I am not
> able to re-seed it with same values, I will loose the continuous and
> reproducible pseudo-random generation after suspend. Aren't this
> expected out of PRNG?

An RNG has to be stateless from the perspective of the caller -- this is the 
core implication of entropy.

Then, if you add the initial seed after the RNG lost its state implies that 
the same sequence of random numbers starts again. I.e. where is the 
randomness?
> 
> > Besides, how do you know that slen is not larger than
> > EXYNOS_RNG_SEED_SIZE?
> 
> Right, there is a overflow here. It should be sizeof(rng->seed_save);

shouldn't it be min(rng->seed_save, slen)?
> 
> Thanks for review!
> 
> Best regards,
> Krzysztof



Ciao
Stephan

[PATCH 1/3] crypto: hw_random - Add new Exynos RNG driver

[Krzysztof Kozlowski]

On Fri, Mar 24, 2017 at 03:46:44PM +0100, Stephan M?ller wrote:
> Am Freitag, 24. M?rz 2017, 15:43:48 CET schrieb Krzysztof Kozlowski:
> 
> Hi Krzysztof,
> 
> > On Fri, Mar 24, 2017 at 03:37:59PM +0100, Stephan M?ller wrote:
> > > Am Freitag, 24. M?rz 2017, 15:24:44 CET schrieb Krzysztof Kozlowski:
> > > 
> > > Hi Krzysztof,
> > > 
> > > > +
> > > > +static int exynos_rng_set_seed(struct exynos_rng_dev *rng,
> > > > +			       const u8 *seed, unsigned int slen)
> > > > +{
> > > > +	int ret, i;
> > > > +	u32 val;
> > > > +
> > > > +	dev_dbg(rng->dev, "Seeding with %u bytes\n", slen);
> > > > +
> > > > +	ret = clk_prepare_enable(rng->clk);
> > > > +	if (ret)
> > > > +		return ret;
> > > > +
> > > > +	if (slen < EXYNOS_RNG_SEED_SIZE) {
> > > > +		dev_warn(rng->dev, "Seed too short (only %u bytes)\n", slen);
> > > > +		ret = -EINVAL;
> > > > +		goto out;
> > > > +	}
> > > > +
> > > > +	for (i = 0 ; i < EXYNOS_RNG_SEED_REGS ; i++) {
> > > > +		val = seed[i * 4] << 24;
> > > > +		val |= seed[i * 4 + 1] << 16;
> > > > +		val |= seed[i * 4 + 2] << 8;
> > > > +		val |= seed[i * 4 + 3] << 0;
> > > > +
> > > > +		exynos_rng_writel(rng, val, EXYNOS_RNG_SEED(i));
> > > > +	}
> > > > +
> > > > +	val = exynos_rng_readl(rng, EXYNOS_RNG_STATUS);
> > > > +	if (!(val & EXYNOS_RNG_STATUS_SEED_SETTING_DONE)) {
> > > > +		dev_warn(rng->dev, "Seed setting not finished\n");
> > > > +		ret = -EIO;
> > > > +		goto out;
> > > > +	}
> > > > +
> > > > +	ret = 0;
> > > > +	/* Save seed for suspend */
> > > > +	memcpy(rng->seed_save, seed, slen);
> > > 
> > > Is this really necessary? If you need to save some seed, shouldn't that be
> > > an output of the DRNG and not the real seed?
> > 
> > When suspended to RAM device will loose the contents of registers
> > (including SEED registers) so it has to be initialized with something on
> > resume.
> > 
> > The seed registers are write-only so I cannot read them and store
> > contents just before suspend.
> > 
> > I understand that real seed should not be stored... but then if I am not
> > able to re-seed it with same values, I will loose the continuous and
> > reproducible pseudo-random generation after suspend. Aren't this
> > expected out of PRNG?
> 
> An RNG has to be stateless from the perspective of the caller -- this is the 
> core implication of entropy.
> 
> Then, if you add the initial seed after the RNG lost its state implies that 
> the same sequence of random numbers starts again. I.e. where is the 
> randomness?

Ahhh, yes, you are right. The device would not continue on its random
generation because all state is lost anyway.

I'll use the generated random numbers.

> > > Besides, how do you know that slen is not larger than
> > > EXYNOS_RNG_SEED_SIZE?
> > 
> > Right, there is a overflow here. It should be sizeof(rng->seed_save);
> 
> shouldn't it be min(rng->seed_save, slen)?

Now it is irrelevant but anyway I am not allowing the seed to be less
then EXYNOS_RNG_SEED_SIZE (== sizeof(rng->seed_save)). The device
expects all five channels (registers) to be seeded.

Best regards,
Krzysztof

[PATCH 1/3] crypto: hw_random - Add new Exynos RNG driver

[Stephan Müller]

Am Freitag, 24. M?rz 2017, 15:51:56 CET schrieb Krzysztof Kozlowski:

Hi Krzysztof,
> 
> I'll use the generated random numbers.

If you do that, may I propse that you update this seed field periodically? 
E.g. with every (or every other) user request for random data, you may update 
that field with new data.

Ciao
Stephan

[PATCH 1/3] crypto: hw_random - Add new Exynos RNG driver

[Krzysztof Kozlowski]

On Fri, Mar 24, 2017 at 03:55:22PM +0100, Stephan M?ller wrote:
> Am Freitag, 24. M?rz 2017, 15:51:56 CET schrieb Krzysztof Kozlowski:
> 
> Hi Krzysztof,
> > 
> > I'll use the generated random numbers.
> 
> If you do that, may I propse that you update this seed field periodically? 
> E.g. with every (or every other) user request for random data, you may update 
> that field with new data.

Sounds reasonable. Thanks for feedback, it is much appreciated.

Best regards,
Krzysztof

[PATCH 1/3] crypto: hw_random - Add new Exynos RNG driver

[Bartlomiej Zolnierkiewicz]

Hi,

Firstly, thanks for working on this.

The patch looks fine overall for me, some review comments below.

On Friday, March 24, 2017 05:24:44 PM Krzysztof Kozlowski wrote:
> Replace existing hw_ranndom/exynos-rng driver with a new, reworked one.
> This is a driver for pseudo random number generator block which on
> Exynos4 chipsets must be seeded with some value.  On newer Exynos5420
> chipsets it might seed itself from true random number generator block
> but this is not implemented yet.
> 
> New driver is a complete rework to use the crypto ALGAPI instead of
> hw_random API.  Rationale for the change:
> 1. hw_random interface is for true RNG devices.
> 2. The old driver was seeding itself with jiffies which is not a
>    reliable source for randomness.
> 3. Device generates five random numbers in each pass but old driver was
>    returning only one thus its performance was reduced.
> 
> Compatibility with DeviceTree bindings is preserved.
> 
> New driver does not use runtime power management but manually enables
> and disables the clock when needed.  This is preferred approach because
> using runtime PM just to toggle clock is huge overhead.  Another

I'm not entirely convinced that the new approach is better.

With the old approach exynos_rng_generate() can be called more
than once before PM autosuspend kicks in and thus clk_prepare_enable()/
clk_disable()_unprepare() operations will be done only once. This
would give better performance on the "burst" operations.

[ The above assumes that clock operations are more costly than
  going through PM core to check the current device state. ]

> +static int exynos_rng_get_random(struct exynos_rng_dev *rng,
> +				 u8 *dst, unsigned int dlen,
> +				 unsigned int *read)
> +{
> +	int retry = 100;

I know that this is copied verbatim from the old driver but please
use define for the maximum number of retries.

> +static int exynos_rng_probe(struct platform_device *pdev)
> +{
> +	struct exynos_rng_dev *rng;
> +	struct resource *res;
> +	int ret;
> +
> +	if (exynos_rng_dev)
> +		return -EEXIST;

How this condition could ever happen? 

The probe function will never be called twice.

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics

[PATCH 1/3] crypto: hw_random - Add new Exynos RNG driver

[Krzysztof Kozlowski]

On Fri, Mar 24, 2017 at 04:26:47PM +0100, Bartlomiej Zolnierkiewicz wrote:
> 
> Hi,
> 
> Firstly, thanks for working on this.
> 
> The patch looks fine overall for me, some review comments below.
> 
> On Friday, March 24, 2017 05:24:44 PM Krzysztof Kozlowski wrote:
> > Replace existing hw_ranndom/exynos-rng driver with a new, reworked one.
> > This is a driver for pseudo random number generator block which on
> > Exynos4 chipsets must be seeded with some value.  On newer Exynos5420
> > chipsets it might seed itself from true random number generator block
> > but this is not implemented yet.
> > 
> > New driver is a complete rework to use the crypto ALGAPI instead of
> > hw_random API.  Rationale for the change:
> > 1. hw_random interface is for true RNG devices.
> > 2. The old driver was seeding itself with jiffies which is not a
> >    reliable source for randomness.
> > 3. Device generates five random numbers in each pass but old driver was
> >    returning only one thus its performance was reduced.
> > 
> > Compatibility with DeviceTree bindings is preserved.
> > 
> > New driver does not use runtime power management but manually enables
> > and disables the clock when needed.  This is preferred approach because
> > using runtime PM just to toggle clock is huge overhead.  Another
> 
> I'm not entirely convinced that the new approach is better.
> 
> With the old approach exynos_rng_generate() can be called more
> than once before PM autosuspend kicks in and thus clk_prepare_enable()/
> clk_disable()_unprepare() operations will be done only once. This
> would give better performance on the "burst" operations.
> 
> [ The above assumes that clock operations are more costly than
>   going through PM core to check the current device state. ]

I agree that we loose the "burst" mode but:
1. At least on Exynso4 SSS is part of TOP power domain so it will not
   help to reduce any more power consumption (on Exynos5422 it is
   mentioned in G2D... which seems incorrect).
2. I think the overhead of clk operations is much smaller. These are only
   two locks (prepare mutex + enable spin), simple tree traversal and
   play with few SFRs.

   The power domain code in comparison to that is huge and complicated
   with inter-device links and dependencies. Also the actual runtime PM
   suspend would anyway fall back at then end to clk prepare/enable
   locks and paths.

   We've been talking about this a lot with Marek Szyprowski (cc'ed) and
   he was always (AFAIR) against attempts of runtime power
   management of a single clock...


> 
> > +static int exynos_rng_get_random(struct exynos_rng_dev *rng,
> > +				 u8 *dst, unsigned int dlen,
> > +				 unsigned int *read)
> > +{
> > +	int retry = 100;
> 
> I know that this is copied verbatim from the old driver but please
> use define for the maximum number of retries.

No problem. Number is chosen arbitrarily so there will not be any
additional information coming from the define.

> > +static int exynos_rng_probe(struct platform_device *pdev)
> > +{
> > +	struct exynos_rng_dev *rng;
> > +	struct resource *res;
> > +	int ret;
> > +
> > +	if (exynos_rng_dev)
> > +		return -EEXIST;
> 
> How this condition could ever happen? 
> 
> The probe function will never be called twice.

I really do not like global or file-scope variables. I do not like
drivers using them. Actually I hate them.

>From time to time I encounter a driver which was designed with that
approach - static fields and hidden assumption that there will be only
one instance. Usually that assumption is really hidden...

... and then it happens that I want to use two instances which of course
fails.

This code serves as a clear documentation for this assumption - only one
instance is allowed. You can look at it as a self-documenting
requirement.

And I think the probe might be called twice, for example in case of
mistake in DTB.

Best regards,
Krzysztof

[PATCH 1/3] crypto: hw_random - Add new Exynos RNG driver

[Bartlomiej Zolnierkiewicz]

On Friday, March 24, 2017 06:46:00 PM Krzysztof Kozlowski wrote:
> On Fri, Mar 24, 2017 at 04:26:47PM +0100, Bartlomiej Zolnierkiewicz wrote:
> > 
> > Hi,
> > 
> > Firstly, thanks for working on this.
> > 
> > The patch looks fine overall for me, some review comments below.
> > 
> > On Friday, March 24, 2017 05:24:44 PM Krzysztof Kozlowski wrote:
> > > Replace existing hw_ranndom/exynos-rng driver with a new, reworked one.
> > > This is a driver for pseudo random number generator block which on
> > > Exynos4 chipsets must be seeded with some value.  On newer Exynos5420
> > > chipsets it might seed itself from true random number generator block
> > > but this is not implemented yet.
> > > 
> > > New driver is a complete rework to use the crypto ALGAPI instead of
> > > hw_random API.  Rationale for the change:
> > > 1. hw_random interface is for true RNG devices.
> > > 2. The old driver was seeding itself with jiffies which is not a
> > >    reliable source for randomness.
> > > 3. Device generates five random numbers in each pass but old driver was
> > >    returning only one thus its performance was reduced.
> > > 
> > > Compatibility with DeviceTree bindings is preserved.
> > > 
> > > New driver does not use runtime power management but manually enables
> > > and disables the clock when needed.  This is preferred approach because
> > > using runtime PM just to toggle clock is huge overhead.  Another
> > 
> > I'm not entirely convinced that the new approach is better.
> > 
> > With the old approach exynos_rng_generate() can be called more
> > than once before PM autosuspend kicks in and thus clk_prepare_enable()/
> > clk_disable()_unprepare() operations will be done only once. This
> > would give better performance on the "burst" operations.
> > 
> > [ The above assumes that clock operations are more costly than
> >   going through PM core to check the current device state. ]
> 
> I agree that we loose the "burst" mode but:
> 1. At least on Exynso4 SSS is part of TOP power domain so it will not
>    help to reduce any more power consumption (on Exynos5422 it is
>    mentioned in G2D... which seems incorrect).
> 2. I think the overhead of clk operations is much smaller. These are only
>    two locks (prepare mutex + enable spin), simple tree traversal and
>    play with few SFRs.
> 
>    The power domain code in comparison to that is huge and complicated
>    with inter-device links and dependencies. Also the actual runtime PM
>    suspend would anyway fall back at then end to clk prepare/enable
>    locks and paths.
> 
>    We've been talking about this a lot with Marek Szyprowski (cc'ed) and
>    he was always (AFAIR) against attempts of runtime power
>    management of a single clock...

OK, thanks for explanation.

> > > +static int exynos_rng_probe(struct platform_device *pdev)
> > > +{
> > > +	struct exynos_rng_dev *rng;
> > > +	struct resource *res;
> > > +	int ret;
> > > +
> > > +	if (exynos_rng_dev)
> > > +		return -EEXIST;
> > 
> > How this condition could ever happen? 
> > 
> > The probe function will never be called twice.
> 
> I really do not like global or file-scope variables. I do not like
> drivers using them. Actually I hate them.
> 
> From time to time I encounter a driver which was designed with that
> approach - static fields and hidden assumption that there will be only
> one instance. Usually that assumption is really hidden...
> 
> ... and then it happens that I want to use two instances which of course
> fails.
> 
> This code serves as a clear documentation for this assumption - only one
> instance is allowed. You can look at it as a self-documenting
> requirement.

For me it looks as needless case of defensive programming and when
I see the code like this it always raises questions about the real
intentions of the code. I find it puzzling and not helpful.

> And I think the probe might be called twice, for example in case of
> mistake in DTB.

Even if this is possible resource allocation code in the driver will
take take care of handling it just fine,

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics

[PATCH 1/3] crypto: hw_random - Add new Exynos RNG driver

[Krzysztof Kozlowski]

On Fri, Mar 24, 2017 at 05:11:25PM +0100, Bartlomiej Zolnierkiewicz wrote:
> On Friday, March 24, 2017 06:46:00 PM Krzysztof Kozlowski wrote:
> > I really do not like global or file-scope variables. I do not like
> > drivers using them. Actually I hate them.
> > 
> > From time to time I encounter a driver which was designed with that
> > approach - static fields and hidden assumption that there will be only
> > one instance. Usually that assumption is really hidden...
> > 
> > ... and then it happens that I want to use two instances which of course
> > fails.
> > 
> > This code serves as a clear documentation for this assumption - only one
> > instance is allowed. You can look at it as a self-documenting
> > requirement.
> 
> For me it looks as needless case of defensive programming and when
> I see the code like this it always raises questions about the real
> intentions of the code. I find it puzzling and not helpful.

I do not understand what might be puzzling about check for static
file-scope value. It is of course subjective, but for me that looks
pretty self-explanatory.

> 
> > And I think the probe might be called twice, for example in case of
> > mistake in DTB.
> 
> Even if this is possible resource allocation code in the driver will
> take take care of handling it just fine,

Indeed, the devm_ioremap_resource() solves the case. I can drop the
check then.

Best regards,
Krzysztof

[PATCH 1/3] crypto: hw_random - Add new Exynos RNG driver

[Bartlomiej Zolnierkiewicz]

On Friday, March 24, 2017 07:19:34 PM Krzysztof Kozlowski wrote:
> On Fri, Mar 24, 2017 at 05:11:25PM +0100, Bartlomiej Zolnierkiewicz wrote:
> > On Friday, March 24, 2017 06:46:00 PM Krzysztof Kozlowski wrote:
> > > I really do not like global or file-scope variables. I do not like
> > > drivers using them. Actually I hate them.
> > > 
> > > From time to time I encounter a driver which was designed with that
> > > approach - static fields and hidden assumption that there will be only
> > > one instance. Usually that assumption is really hidden...
> > > 
> > > ... and then it happens that I want to use two instances which of course
> > > fails.
> > > 
> > > This code serves as a clear documentation for this assumption - only one
> > > instance is allowed. You can look at it as a self-documenting
> > > requirement.
> > 
> > For me it looks as needless case of defensive programming and when
> > I see the code like this it always raises questions about the real
> > intentions of the code. I find it puzzling and not helpful.
> 
> I do not understand what might be puzzling about check for static
> file-scope value. It is of course subjective, but for me that looks
> pretty self-explanatory.

The check should never happen given that ->probe will not happen twice.

However it seems that this is possible now with DT platform devices and
incorrect DTB.

> > > And I think the probe might be called twice, for example in case of
> > > mistake in DTB.
> > 
> > Even if this is possible resource allocation code in the driver will
> > take take care of handling it just fine,
> 
> Indeed, the devm_ioremap_resource() solves the case. I can drop the
> check then.

Looking on this a bit more it seems that devm_ioremap_resource() will
not cover all mistakes (using compatible by mistake in some other DTB
node).

Leave the check, I take my objection back.

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics

[PATCH 1/3] crypto: hw_random - Add new Exynos RNG driver

[Krzysztof Kozlowski]

On Fri, Mar 24, 2017 at 05:45:41PM +0100, Bartlomiej Zolnierkiewicz wrote:
> > > > And I think the probe might be called twice, for example in case of
> > > > mistake in DTB.
> > > 
> > > Even if this is possible resource allocation code in the driver will
> > > take take care of handling it just fine,
> > 
> > Indeed, the devm_ioremap_resource() solves the case. I can drop the
> > check then.
> 
> Looking on this a bit more it seems that devm_ioremap_resource() will
> not cover all mistakes (using compatible by mistake in some other DTB
> node).
> 
> Leave the check, I take my objection back.

Great! Thanks for feedback.

Best regards,
Krzysztof

[PATCH 2/3] ARM: exynos_defconfig: Enable Exynos RNG and user-space crypto API

[Krzysztof Kozlowski]

Enable the new Exynos pseudo random number generator driver and
user-space API to access crypto algorithms and devices (not only RNG).

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
---
 arch/arm/configs/exynos_defconfig | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm/configs/exynos_defconfig b/arch/arm/configs/exynos_defconfig
index 6dc661c4a2c1..960d55445e05 100644
--- a/arch/arm/configs/exynos_defconfig
+++ b/arch/arm/configs/exynos_defconfig
@@ -265,6 +265,12 @@ CONFIG_DEBUG_RT_MUTEXES=y
 CONFIG_DEBUG_SPINLOCK=y
 CONFIG_DEBUG_MUTEXES=y
 CONFIG_DEBUG_USER=y
+CONFIG_CRYPTO_USER=m
+CONFIG_CRYPTO_USER_API_HASH=m
+CONFIG_CRYPTO_USER_API_SKCIPHER=m
+CONFIG_CRYPTO_USER_API_RNG=m
+CONFIG_CRYPTO_USER_API_AEAD=m
+CONFIG_CRYPTO_DEV_EXYNOS_RNG=y
 CONFIG_CRYPTO_DEV_S5P=y
 CONFIG_ARM_CRYPTO=y
 CONFIG_CRYPTO_SHA1_ARM_NEON=m
-- 
2.9.3

[PATCH 3/3] ARM: multi_v7_defconfig: Enable Exynos RNG and user-space crypto API

[Krzysztof Kozlowski]

Enable the new Exynos pseudo random number generator driver and
user-space API to access crypto algorithms and devices (not only RNG).

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
---
 arch/arm/configs/multi_v7_defconfig | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm/configs/multi_v7_defconfig b/arch/arm/configs/multi_v7_defconfig
index 36c1b39cfb54..9bc1bd7f2afa 100644
--- a/arch/arm/configs/multi_v7_defconfig
+++ b/arch/arm/configs/multi_v7_defconfig
@@ -935,7 +935,13 @@ CONFIG_CPUFREQ_DT=y
 CONFIG_KEYSTONE_IRQ=y
 CONFIG_HW_RANDOM=y
 CONFIG_HW_RANDOM_ST=y
+CONFIG_CRYPTO_USER=m
+CONFIG_CRYPTO_USER_API_HASH=m
+CONFIG_CRYPTO_USER_API_SKCIPHER=m
+CONFIG_CRYPTO_USER_API_RNG=m
+CONFIG_CRYPTO_USER_API_AEAD=m
 CONFIG_CRYPTO_DEV_MARVELL_CESA=m
+CONFIG_CRYPTO_DEV_EXYNOS_RNG=m
 CONFIG_CRYPTO_DEV_S5P=m
 CONFIG_CRYPTO_DEV_SUN4I_SS=m
 CONFIG_CRYPTO_DEV_ROCKCHIP=m
-- 
2.9.3