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authorAlex Porosanu <alexandru.porosanu@freescale.com>2014-08-11 12:40:16 +0400
committerHerbert Xu <herbert@gondor.apana.org.au>2014-08-25 16:32:35 +0400
commiteeaa1724a2e9c8958a8621b3c10d5ca0667e78fa (patch)
tree14853c2ae36391f4fa5f5aa55529e754a08f7488 /drivers/crypto
parentb061f3fefcffa0cdcdc61ae2a1123a4e7697d452 (diff)
downloadlinux-eeaa1724a2e9c8958a8621b3c10d5ca0667e78fa.tar.xz
crypto: caam - change starting entropy delay value
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 <alexandru.porosanu@freescale.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'drivers/crypto')
-rw-r--r--drivers/crypto/caam/ctrl.c9
-rw-r--r--drivers/crypto/caam/regs.h2
2 files changed, 10 insertions, 1 deletions
diff --git a/drivers/crypto/caam/ctrl.c b/drivers/crypto/caam/ctrl.c
index 8908d040b1f2..111ac1ffbc11 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 b8bd980ac00a..5fa739c290a7 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 {