This series of patches target the RNG4 block of CAAM and fix an
issue identified on new platforms using this IP.
Two of the patches, change the way the entropy is being taken
from the internal oscillator and adjust the delay accordingly.
Alex Porosanu (3):
crypto: caam - disable RNG oscillator maximum frequency check
crypto: caam - change starting entropy delay value
crypto: caam - enable raw data instead of von Neumann data
drivers/crypto/caam/ctrl.c | 24 +++++++++++++++++++++---
drivers/crypto/caam/regs.h | 13 ++++++++++++-
2 files changed, 33 insertions(+), 4 deletions(-)
--
1.8.3.1
The rtfrqmax & rtfrqmin set the bounds of the expected frequency of the
oscillator, when SEC runs at its maximum frequency. For certain platforms
(f.i. T2080), the oscillator is very fast and thus if the SEC runs at
a lower than normal frequency, the ring oscillator is incorrectly detected
as being out of bounds.
This patch effectively disables the maximum frequency check, by setting a
high enough maximum allowable frequency for the oscillator. The reasoning
behind this is that usually a broken oscillator will run too slow
(i.e. not run at all) rather than run too fast.
Signed-off-by: Alex Porosanu <[email protected]>
---
drivers/crypto/caam/ctrl.c | 4 ++--
drivers/crypto/caam/regs.h | 1 +
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/crypto/caam/ctrl.c b/drivers/crypto/caam/ctrl.c
index 3cade79..8908d04 100644
--- a/drivers/crypto/caam/ctrl.c
+++ b/drivers/crypto/caam/ctrl.c
@@ -355,8 +355,8 @@ static void kick_trng(struct platform_device *pdev, int ent_delay)
wr_reg32(&r4tst->rtsdctl, val);
/* min. freq. count, equal to 1/4 of the entropy sample length */
wr_reg32(&r4tst->rtfrqmin, ent_delay >> 2);
- /* max. freq. count, equal to 8 times the entropy sample length */
- wr_reg32(&r4tst->rtfrqmax, ent_delay << 3);
+ /* disable maximum frequency count */
+ wr_reg32(&r4tst->rtfrqmax, RTFRQMAX_DISABLE);
/* put RNG4 into run mode */
clrbits32(&r4tst->rtmctl, RTMCTL_PRGM);
}
diff --git a/drivers/crypto/caam/regs.h b/drivers/crypto/caam/regs.h
index f48e344..b8bd980 100644
--- a/drivers/crypto/caam/regs.h
+++ b/drivers/crypto/caam/regs.h
@@ -286,6 +286,7 @@ struct rng4tst {
u32 rttotsam; /* PRGM=0: total samples register */
};
u32 rtfrqmin; /* frequency count min. limit register */
+#define RTFRQMAX_DISABLE (1 << 20)
union {
u32 rtfrqmax; /* PRGM=1: freq. count max. limit register */
u32 rtfrqcnt; /* PRGM=0: freq. count register */
--
1.8.3.1
The entropy delay (the length in system clocks of each
entropy sample) for the RNG4 block of CAAM is dependent
on the frequency of the SoC. By elaborate methods, it
has been determined that a good starting value for all
platforms integrating the CAAM IP is 3200. Using a
higher value has additional benefit of speeding up
the process of instantiating the RNG, since the entropy
delay will be increased and instantiation of the RNG
state handles will be reattempted by the driver. If the
starting value is low, for certain platforms, this can
lead to a quite lengthy process.
This patch changes the starting value of the length of
the entropy sample to 3200 system clocks.
In addition to this change, the attempted entropy delay
values are now printed on the console upon initialization
of the RNG block.
While here, a safeguard for yielding the processor was
added for ensuring that in very adverse cases,
the CPU isn't hogged by the instantiation loop.
Signed-off-by: Alex Porosanu <[email protected]>
---
drivers/crypto/caam/ctrl.c | 9 +++++++++
drivers/crypto/caam/regs.h | 2 +-
2 files changed, 10 insertions(+), 1 deletion(-)
diff --git a/drivers/crypto/caam/ctrl.c b/drivers/crypto/caam/ctrl.c
index 8908d04..111ac1f 100644
--- a/drivers/crypto/caam/ctrl.c
+++ b/drivers/crypto/caam/ctrl.c
@@ -544,6 +544,9 @@ static int caam_probe(struct platform_device *pdev)
* the TRNG parameters.
*/
if (!(ctrlpriv->rng4_sh_init || inst_handles)) {
+ dev_info(dev,
+ "Entropy delay = %u\n",
+ ent_delay);
kick_trng(pdev, ent_delay);
ent_delay += 400;
}
@@ -556,6 +559,12 @@ static int caam_probe(struct platform_device *pdev)
*/
ret = instantiate_rng(dev, inst_handles,
gen_sk);
+ if (ret == -EAGAIN)
+ /*
+ * if here, the loop will rerun,
+ * so don't hog the CPU
+ */
+ cpu_relax();
} while ((ret == -EAGAIN) && (ent_delay < RTSDCTL_ENT_DLY_MAX));
if (ret) {
dev_err(dev, "failed to instantiate RNG");
diff --git a/drivers/crypto/caam/regs.h b/drivers/crypto/caam/regs.h
index b8bd980..5fa739c 100644
--- a/drivers/crypto/caam/regs.h
+++ b/drivers/crypto/caam/regs.h
@@ -278,7 +278,7 @@ struct rng4tst {
};
#define RTSDCTL_ENT_DLY_SHIFT 16
#define RTSDCTL_ENT_DLY_MASK (0xffff << RTSDCTL_ENT_DLY_SHIFT)
-#define RTSDCTL_ENT_DLY_MIN 1200
+#define RTSDCTL_ENT_DLY_MIN 3200
#define RTSDCTL_ENT_DLY_MAX 12800
u32 rtsdctl; /* seed control register */
union {
--
1.8.3.1
The sampling of the oscillator can be done in multiple modes for
generating the entropy value. By default, this is set to von
Neumann. This patch changes the sampling to raw data, since it
has been discovered that the generated entropy has a better
'quality'.
Signed-off-by: Alex Porosanu <[email protected]>
---
drivers/crypto/caam/ctrl.c | 11 ++++++++++-
drivers/crypto/caam/regs.h | 10 ++++++++++
2 files changed, 20 insertions(+), 1 deletion(-)
diff --git a/drivers/crypto/caam/ctrl.c b/drivers/crypto/caam/ctrl.c
index 111ac1f..c621037 100644
--- a/drivers/crypto/caam/ctrl.c
+++ b/drivers/crypto/caam/ctrl.c
@@ -357,8 +357,17 @@ static void kick_trng(struct platform_device *pdev, int ent_delay)
wr_reg32(&r4tst->rtfrqmin, ent_delay >> 2);
/* disable maximum frequency count */
wr_reg32(&r4tst->rtfrqmax, RTFRQMAX_DISABLE);
+ /* read the control register */
+ val = rd_reg32(&r4tst->rtmctl);
+ /*
+ * select raw sampling in both entropy shifter
+ * and statistical checker
+ */
+ setbits32(&val, RTMCTL_SAMP_MODE_RAW_ES_SC);
/* put RNG4 into run mode */
- clrbits32(&r4tst->rtmctl, RTMCTL_PRGM);
+ clrbits32(&val, RTMCTL_PRGM);
+ /* write back the control register */
+ wr_reg32(&r4tst->rtmctl, val);
}
/**
diff --git a/drivers/crypto/caam/regs.h b/drivers/crypto/caam/regs.h
index 5fa739c..bc9cd62 100644
--- a/drivers/crypto/caam/regs.h
+++ b/drivers/crypto/caam/regs.h
@@ -269,6 +269,16 @@ struct rngtst {
/* RNG4 TRNG test registers */
struct rng4tst {
#define RTMCTL_PRGM 0x00010000 /* 1 -> program mode, 0 -> run mode */
+#define RTMCTL_SAMP_MODE_VON_NEUMANN_ES_SC 0 /* use von Neumann data in
+ both entropy shifter and
+ statistical checker */
+#define RTMCTL_SAMP_MODE_RAW_ES_SC 1 /* use raw data in both
+ entropy shifter and
+ statistical checker */
+#define RTMCTL_SAMP_MODE_VON_NEUMANN_ES_RAW_SC 2 /* use von Neumann data in
+ entropy shifter, raw data
+ in statistical checker */
+#define RTMCTL_SAMP_MODE_INVALID 3 /* invalid combination */
u32 rtmctl; /* misc. control register */
u32 rtscmisc; /* statistical check misc. register */
u32 rtpkrrng; /* poker range register */
--
1.8.3.1
On Mon, Aug 11, 2014 at 11:40:14AM +0300, Alex Porosanu wrote:
> This series of patches target the RNG4 block of CAAM and fix an
> issue identified on new platforms using this IP.
> Two of the patches, change the way the entropy is being taken
> from the internal oscillator and adjust the delay accordingly.
>
> Alex Porosanu (3):
> crypto: caam - disable RNG oscillator maximum frequency check
> crypto: caam - change starting entropy delay value
> crypto: caam - enable raw data instead of von Neumann data
All applied.
--
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt