[PATCH v4 2/2] 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 32-bit numbers in each pass but old
   driver was returning only one 32-bit number 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 reseeding itself with generated random data
periodically and during resuming from system suspend (previously driver
was re-seeding itself again with jiffies).

Signed-off-by: Krzysztof Kozlowski 
Reviewed-by: Stephan Müller 
Reviewed-by: PrasannaKumar Muralidharan 
---
 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 | 389 
 7 files changed, 413 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-de...@alsa-project.org (moderated for 
non-subscribers)
 S: Supported
 F: sound/soc/samsung/
 
+SAMSUNG EXYNOS PSEUDO RANDOM NUMBER GENERATOR (RNG) DRIVER
+M: Krzysztof Kozlowski 
+L: linux-crypto@vger.kernel.org
+L: linux-samsung-...@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 
 L: linux-fb...@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..
--- 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 
- *
- * 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, 

[PATCH v4 0/2] crypto: hw_random - Add new Exynos RNG driver

[Krzysztof Kozlowski]

Hi,

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

Changes since v3:
=
1. New patch: 1/2 for ALIGN_DOWN macro. The change in metag architecture
   was not compiled. Please test it.
2. Dropped patches touching ARM defconfig as they are not changing and
   they pollute this submission.
3. Utilize all seed provided by kcapi (suggested by Stephan Müller).
4. Drop dev->ctx (suggested by PrasannaKumar Muralidharan).
5. Remove any printks from set_seed callback as this might be a way
   for unprivileged user to pollute the log (suggested by Stephan).
6. Minor cleanups: initialize 'read' variable in exynos_rng_reseed()
   for readability (it is not strictly required).
7. Add review tags from Stephen and PrasannaKumar.


Changes since v2:
=
1. Do not re-use random numbers for re-seed (neither for system resume
   nor for periodic re-seed).  Instead the driver will just generate new
   random numbers (suggested by Stephan Müller).

   Suspend path tested with suspend-to-freeze, not real suspend. Testing
   on Trats2 would be welcomed.

Changes since v1:
=
1. Re-work the code for seeding after system resume, following suggestions
   and review by Stephan Müller.

2. Re-seed itself from time to time (every 100 ms), suggested by Stephan
   Müller.

3. Use a define for retries (Bartlomiej Zolnierkiewicz).
4. Add some docs.


Description:

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 (2):
  linux/kernel.h: Add ALIGN_DOWN macro
  crypto: hw_random - Add new Exynos RNG driver

 MAINTAINERS |   8 +
 arch/metag/kernel/stacktrace.c  |   2 -
 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 | 389 
 drivers/gpu/drm/udl/udl_fb.c|   2 +-
 include/linux/kernel.h  |   1 +
 include/video/udlfb.h   |   2 +-
 11 files changed, 416 insertions(+), 250 deletions(-)
 delete mode 100644 drivers/char/hw_random/exynos-rng.c
 create mode 100644 drivers/crypto/exynos-rng.c

-- 
2.9.3

[PATCH v4 1/2] linux/kernel.h: Add ALIGN_DOWN macro

[Krzysztof Kozlowski]

Few parts of kernel define their own macro for aligning down so provide
a common define for this, with the same usage and assumptions as existing
ALIGN.

Convert also three existing implementations to this one.

Signed-off-by: Krzysztof Kozlowski 

---

The metag change was not even compiled due to lack of cross compiler.
---
 arch/metag/kernel/stacktrace.c | 2 --
 drivers/gpu/drm/udl/udl_fb.c   | 2 +-
 include/linux/kernel.h | 1 +
 include/video/udlfb.h  | 2 +-
 4 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/metag/kernel/stacktrace.c b/arch/metag/kernel/stacktrace.c
index 91ffc4b75c33..09d67b7f51ca 100644
--- a/arch/metag/kernel/stacktrace.c
+++ b/arch/metag/kernel/stacktrace.c
@@ -31,8 +31,6 @@ static void tbi_boing_init(void)
 }
 #endif
 
-#define ALIGN_DOWN(addr, size)  ((addr)&(~((size)-1)))
-
 /*
  * Unwind the current stack frame and store the new register values in the
  * structure passed as argument. Unwinding is equivalent to a function return,
diff --git a/drivers/gpu/drm/udl/udl_fb.c b/drivers/gpu/drm/udl/udl_fb.c
index d05abc69e305..4a6500362564 100644
--- a/drivers/gpu/drm/udl/udl_fb.c
+++ b/drivers/gpu/drm/udl/udl_fb.c
@@ -37,7 +37,7 @@ struct udl_fbdev {
 };
 
 #define DL_ALIGN_UP(x, a) ALIGN(x, a)
-#define DL_ALIGN_DOWN(x, a) ALIGN(x-(a-1), a)
+#define DL_ALIGN_DOWN(x, a) ALIGN_DOWN(x, a)
 
 /** Read the red component (0..255) of a 32 bpp colour. */
 #define DLO_RGB_GETRED(col) (uint8_t)((col) & 0xFF)
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 4c26dc3a8295..3d9f8420f973 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -47,6 +47,7 @@
 
 /* @a is a power of 2 value */
 #define ALIGN(x, a)__ALIGN_KERNEL((x), (a))
+#define ALIGN_DOWN(x, a)   __ALIGN_KERNEL((x) - ((a) - 1), (a))
 #define __ALIGN_MASK(x, mask)  __ALIGN_KERNEL_MASK((x), (mask))
 #define PTR_ALIGN(p, a)((typeof(p))ALIGN((unsigned long)(p), 
(a)))
 #define IS_ALIGNED(x, a)   (((x) & ((typeof(x))(a) - 1)) == 0)
diff --git a/include/video/udlfb.h b/include/video/udlfb.h
index f9466fa54ba4..3ea90aea5617 100644
--- a/include/video/udlfb.h
+++ b/include/video/udlfb.h
@@ -92,6 +92,6 @@ struct dlfb_data {
 
 /* remove these once align.h patch is taken into kernel */
 #define DL_ALIGN_UP(x, a) ALIGN(x, a)
-#define DL_ALIGN_DOWN(x, a) ALIGN(x-(a-1), a)
+#define DL_ALIGN_DOWN(x, a) ALIGN_DOWN(x, a)
 
 #endif
-- 
2.9.3