[PATCH v7 10/15] crypto/fsl: Improve hwrng performance in kernel

[Gaurav Jain]

From: Ye Li <ye.li at nxp.com>

RNG parameters are reconfigured.
- For TRNG to generate 256 bits of entropy, RNG TRNG Seed Control register
  is configured to have reduced SAMP_SIZE from default 2500 to 512. it is
  number of entropy samples that will be taken during Entropy generation.
- self-test registers(Monobit Limit, Poker Range, Run Length Limit)
  are synchronized with new RTSDCTL[SAMP_SIZE] of 512.

TRNG time is caluculated based on sample size.
time required to generate entropy is reduced and
hwrng performance improved from 0.3 kB/s to 1.3 kB/s.

Signed-off-by: Ye Li <ye.li at nxp.com>
Acked-by: Gaurav Jain <gaurav.jain at nxp.com>>
---
 drivers/crypto/fsl/jr.c | 102 +++++++++++++++++++++++++++++++++-------
 include/fsl_sec.h       |   1 +
 2 files changed, 87 insertions(+), 16 deletions(-)

diff --git a/drivers/crypto/fsl/jr.c b/drivers/crypto/fsl/jr.c
index 084a61c684..15f5fd0d05 100644
--- a/drivers/crypto/fsl/jr.c
+++ b/drivers/crypto/fsl/jr.c
@@ -603,30 +603,100 @@ static u8 get_rng_vid(ccsr_sec_t *sec)
  */
 static void kick_trng(int ent_delay, ccsr_sec_t *sec)
 {
+	u32 samples  = 512; /* number of bits to generate and test */
+	u32 mono_min = 195;
+	u32 mono_max = 317;
+	u32 mono_range  = mono_max - mono_min;
+	u32 poker_min = 1031;
+	u32 poker_max = 1600;
+	u32 poker_range = poker_max - poker_min + 1;
+	u32 retries    = 2;
+	u32 lrun_max   = 32;
+	s32 run_1_min   = 27;
+	s32 run_1_max   = 107;
+	s32 run_1_range = run_1_max - run_1_min;
+	s32 run_2_min   = 7;
+	s32 run_2_max   = 62;
+	s32 run_2_range = run_2_max - run_2_min;
+	s32 run_3_min   = 0;
+	s32 run_3_max   = 39;
+	s32 run_3_range = run_3_max - run_3_min;
+	s32 run_4_min   = -1;
+	s32 run_4_max   = 26;
+	s32 run_4_range = run_4_max - run_4_min;
+	s32 run_5_min   = -1;
+	s32 run_5_max   = 18;
+	s32 run_5_range = run_5_max - run_5_min;
+	s32 run_6_min   = -1;
+	s32 run_6_max   = 17;
+	s32 run_6_range = run_6_max - run_6_min;
+	u32 val;
+
 	struct rng4tst __iomem *rng =
 			(struct rng4tst __iomem *)&sec->rng;
-	u32 val;
 
-	/* put RNG4 into program mode */
-	sec_setbits32(&rng->rtmctl, RTMCTL_PRGM);
-	/* rtsdctl bits 0-15 contain "Entropy Delay, which defines the
-	 * length (in system clocks) of each Entropy sample taken
-	 * */
+	/* Put RNG in program mode */
+	/* Setting both RTMCTL:PRGM and RTMCTL:TRNG_ACC causes TRNG to
+	 * properly invalidate the entropy in the entropy register and
+	 * force re-generation.
+	 */
+	sec_setbits32(&rng->rtmctl, RTMCTL_PRGM | RTMCTL_ACC);
+
+	/* Configure the RNG Entropy Delay
+	 * Performance-wise, it does not make sense to
+	 * set the delay to a value that is lower
+	 * than the last one that worked (i.e. the state handles
+	 * were instantiated properly. Thus, instead of wasting
+	 * time trying to set the values controlling the sample
+	 * frequency, the function simply returns.
+	 */
 	val = sec_in32(&rng->rtsdctl);
-	val = (val & ~RTSDCTL_ENT_DLY_MASK) |
-	      (ent_delay << RTSDCTL_ENT_DLY_SHIFT);
+	val &= RTSDCTL_ENT_DLY_MASK;
+	val >>= RTSDCTL_ENT_DLY_SHIFT;
+	if (ent_delay < val) {
+		/* Put RNG4 into run mode */
+		sec_clrbits32(&rng->rtmctl, RTMCTL_PRGM | RTMCTL_ACC);
+		return;
+	}
+
+	val = (ent_delay << RTSDCTL_ENT_DLY_SHIFT) | samples;
 	sec_out32(&rng->rtsdctl, val);
-	/* min. freq. count, equal to 1/4 of the entropy sample length */
-	sec_out32(&rng->rtfreqmin, ent_delay >> 2);
-	/* disable maximum frequency count */
-	sec_out32(&rng->rtfreqmax, RTFRQMAX_DISABLE);
+
+	/*
+	 * Recommended margins (min,max) for freq. count:
+	 *   freq_mul = RO_freq / TRNG_clk_freq
+	 *   rtfrqmin = (ent_delay x freq_mul) >> 1;
+	 *   rtfrqmax = (ent_delay x freq_mul) << 3;
+	 * Given current deployments of CAAM in i.MX SoCs, and to simplify
+	 * the configuration, we consider [1,16] to be a safe interval
+	 * for the freq_mul and the limits of the interval are used to compute
+	 * rtfrqmin, rtfrqmax
+	 */
+	sec_out32(&rng->rtfreqmin, ent_delay >> 1);
+	sec_out32(&rng->rtfreqmax, ent_delay << 7);
+
+	sec_out32(&rng->rtscmisc, (retries << 16) | lrun_max);
+	sec_out32(&rng->rtpkrmax, poker_max);
+	sec_out32(&rng->rtpkrrng, poker_range);
+	sec_out32(&rng->rsvd1[0], (mono_range << 16) | mono_max);
+	sec_out32(&rng->rsvd1[1], (run_1_range << 16) | run_1_max);
+	sec_out32(&rng->rsvd1[2], (run_2_range << 16) | run_2_max);
+	sec_out32(&rng->rsvd1[3], (run_3_range << 16) | run_3_max);
+	sec_out32(&rng->rsvd1[4], (run_4_range << 16) | run_4_max);
+	sec_out32(&rng->rsvd1[5], (run_5_range << 16) | run_5_max);
+	sec_out32(&rng->rsvd1[6], (run_6_range << 16) | run_6_max);
+
+	val = sec_in32(&rng->rtmctl);
 	/*
-	 * select raw sampling in both entropy shifter
+	 * Select raw sampling in both entropy shifter
 	 * and statistical checker
 	 */
-	sec_setbits32(&rng->rtmctl, RTMCTL_SAMP_MODE_RAW_ES_SC);
-	/* put RNG4 into run mode */
-	sec_clrbits32(&rng->rtmctl, RTMCTL_PRGM);
+	val &= ~RTMCTL_SAMP_MODE_INVALID;
+	val |= RTMCTL_SAMP_MODE_RAW_ES_SC;
+	/* Put RNG4 into run mode */
+	val &= ~(RTMCTL_PRGM | RTMCTL_ACC);
+	/*test with sample mode only */
+	sec_out32(&rng->rtmctl, val);
 }
 
 static int rng_init(uint8_t sec_idx, ccsr_sec_t *sec)
diff --git a/include/fsl_sec.h b/include/fsl_sec.h
index 7b6e3e2c20..2b3239414a 100644
--- a/include/fsl_sec.h
+++ b/include/fsl_sec.h
@@ -34,6 +34,7 @@
 #if CONFIG_SYS_FSL_SEC_COMPAT >= 4
 /* RNG4 TRNG test registers */
 struct rng4tst {
+#define RTMCTL_ACC  0x20
 #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
-- 
2.17.1