[PATCH v6 5/7] crypto: caam - invalidate entropy register during RNG initialization

[Andrey Smirnov <andrew.smirnov@gmail.com>]

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