From: Fabio Estevam <festevam@xxxxxxx>
Since commit 358ba762d9f1 ("crypto: caam - enable prediction resistance
in HRWNG") the following CAAM errors can be seen on i.MX6SX:
caam_jr 2101000.jr: 20003c5b: CCB: desc idx 60: RNG: Hardware error
hwrng: no data available
This error is due to an incorrect entropy delay for i.MX6SX.
Fix it by increasing the minimum entropy delay for i.MX6SX
as done in U-Boot:
https://patchwork.ozlabs.org/project/uboot/patch/20220415111049.2565744-1-gaurav.jain@xxxxxxx/
Cc: <stable@xxxxxxxxxxxxxxx>
Fixes: 358ba762d9f1 ("crypto: caam - enable prediction resistance in HRWNG")
Signed-off-by: Fabio Estevam <festevam@xxxxxxx>
---
Changes since v3:
- Add a needs_extended_entropy_delay() function
- Assign the 'ent_delay' inside the the RNG initialization area. (Horia)
- Change the terminology as per Horia's explanation.
drivers/crypto/caam/ctrl.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/drivers/crypto/caam/ctrl.c b/drivers/crypto/caam/ctrl.c
index ca0361b2dbb0..5b989a842ee9 100644
--- a/drivers/crypto/caam/ctrl.c
+++ b/drivers/crypto/caam/ctrl.c
@@ -609,6 +609,13 @@ static bool check_version(struct fsl_mc_version *mc_version, u32 major,
}
#endif
+static bool needs_extended_entropy_delay(void)
+{
+ if (of_machine_is_compatible("fsl,imx6sx"))
+ return true;
+ return false;
+}
+
/* Probe routine for CAAM top (controller) level */
static int caam_probe(struct platform_device *pdev)
{
@@ -855,6 +862,8 @@ static int caam_probe(struct platform_device *pdev)
* Also, if a handle was instantiated, do not change
* the TRNG parameters.
*/
+ if (needs_extended_entropy_delay())
+ ent_delay = 12000;
if (!(ctrlpriv->rng4_sh_init || inst_handles)) {
dev_info(dev,
"Entropy delay = %u\n",
@@ -871,6 +880,15 @@ static int caam_probe(struct platform_device *pdev)
*/
ret = instantiate_rng(dev, inst_handles,
gen_sk);
+ /*
+ * Entropy delay is determined via TRNG characterization.
+ * TRNG characterization is run across different voltages
+ * and temperatures.
+ * If worst case value for ent_dly is identified,
+ * the loop can be skipped for that platform.
+ */
+ if (needs_extended_entropy_delay())
+ break;
if (ret == -EAGAIN)
/*
* if here, the loop will rerun,
--
2.25.1
