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Subject[PATCH v6 5/7] crypto: caam - invalidate entropy register during RNG initialization
Date
In order to make sure that we always use non-stale entropy data, change
the code to invalidate entropy register during RNG initialization.

Signed-off-by: Aymen Sghaier <aymen.sghaier@nxp.com>
Signed-off-by: Vipul Kumar <vipul_kumar@mentor.com>
[andrew.smirnov@gmail.com ported to upstream kernel, rewrote commit msg]
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Cc: Chris Healy <cphealy@gmail.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Horia Geantă <horia.geanta@nxp.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Iuliana Prodan <iuliana.prodan@nxp.com>
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-imx@nxp.com
---
drivers/crypto/caam/ctrl.c | 11 ++++++++---
drivers/crypto/caam/regs.h | 3 ++-
2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/crypto/caam/ctrl.c b/drivers/crypto/caam/ctrl.c
index c99a6a3b22de..22d8676dd610 100644
--- a/drivers/crypto/caam/ctrl.c
+++ b/drivers/crypto/caam/ctrl.c
@@ -338,8 +338,12 @@ static void kick_trng(struct platform_device *pdev, int ent_delay)
ctrl = (struct caam_ctrl __iomem *)ctrlpriv->ctrl;
r4tst = &ctrl->r4tst[0];

- /* put RNG4 into program mode */
- clrsetbits_32(&r4tst->rtmctl, 0, RTMCTL_PRGM);
+ /*
+ * Setting both RTMCTL:PRGM and RTMCTL:TRNG_ACC causes TRNG to
+ * properly invalidate the entropy in the entropy register and
+ * force re-generation.
+ */
+ clrsetbits_32(&r4tst->rtmctl, 0, RTMCTL_PRGM | RTMCTL_ACC);

/*
* Performance-wise, it does not make sense to
@@ -369,7 +373,8 @@ static void kick_trng(struct platform_device *pdev, int ent_delay)
* select raw sampling in both entropy shifter
* and statistical checker; ; put RNG4 into run mode
*/
- clrsetbits_32(&r4tst->rtmctl, RTMCTL_PRGM, RTMCTL_SAMP_MODE_RAW_ES_SC);
+ clrsetbits_32(&r4tst->rtmctl, RTMCTL_PRGM | RTMCTL_ACC,
+ RTMCTL_SAMP_MODE_RAW_ES_SC);
}

static int caam_get_era_from_hw(struct caam_ctrl __iomem *ctrl)
diff --git a/drivers/crypto/caam/regs.h b/drivers/crypto/caam/regs.h
index 05127b70527d..c191e8fd0fa7 100644
--- a/drivers/crypto/caam/regs.h
+++ b/drivers/crypto/caam/regs.h
@@ -487,7 +487,8 @@ struct rngtst {

/* RNG4 TRNG test registers */
struct rng4tst {
-#define RTMCTL_PRGM 0x00010000 /* 1 -> program mode, 0 -> run mode */
+#define RTMCTL_ACC BIT(5) /* TRNG access mode */
+#define RTMCTL_PRGM BIT(16) /* 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 */
--
2.21.0
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