hwrng: bcm2835: add reset support

v5: remove reset_control_rearm() and apply on latest herbert/cryptodev-2.6.git.
v4: fix documentation, add reset_control_rearm().
v3: make resets required if brcm,bcm6368-rng.
v2: document reset support.

Álvaro Fernández Rojas (2):
dt-bindings: rng: bcm2835: document reset support
hwrng: bcm2835: add reset support

 .../devicetree/bindings/rng/brcm,bcm2835.yaml   | 17 +++++++++++++++++
 drivers/char/hw_random/bcm2835-rng.c            | 10 ++++++++++
 2 files changed, 27 insertions(+)

2.20.1

Some devices may need to perform a reset before using the RNG, such as the BCM6368.

---
v5: no changes.
v4: pass dt_binding_check.
v3: make resets required if brcm,bcm6368-rng.
v2: document reset support.

 .../devicetree/bindings/rng/brcm,bcm2835.yaml   | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

index c147900f9041..11c23e1f6988 100644
@@ -37,6 +37,21 @@ required:
 
 additionalProperties: false
 
+if:
+  properties:
+    compatible:
+      enum:
+        - brcm,bcm6368-rng
+then:
+  properties:
+    resets:
+      maxItems: 1
+  required:
+    - resets
+else:
+  properties:
+    resets: false
+
 examples:
   - |
     rng@7e104000 {

@@ -58,4 +73,6 @@ examples:
 
         clocks = <&periph_clk 18>;
         clock-names = "ipsec";
+
+        resets = <&periph_rst 4>;
     };

2.20.1

Sorry Alvaro I missed you sent a v5 already. See my comments in v3.

Regards,
Nicolas

My bot found errors running 'make dt_binding_check' on your patch:

yamllint warnings/errors:

dtschema/dtc warnings/errors:
/builds/robherring/linux-dt-review/Documentation/devicetree/bindings/rng/brcm,bcm2835.example.dt.yaml: rng@10004180: 'resets' does not match any of the regexes: 'pinctrl-[0-9]+'
From schema: /builds/robherring/linux-dt-review/Documentation/devicetree/bindings/rng/brcm,bcm2835.yaml

See https://patchwork.ozlabs.org/patch/1447144

This check can fail if there are any dependencies. The base for a patch series is generally the most recent rc1.

If you already ran 'make dt_binding_check' and didn't see the above error(s), then make sure 'yamllint' is installed and dt-schema is up to date:

pip3 install dtschema --upgrade

Please check and re-submit.

BCM6368 devices need to reset the in order to generate true random numbers. This is what BCM6368 produces without a reset:

root@OpenWrt:/# cat /dev/hwrng | rngtest -c 1000
rngtest 6.10
Copyright (c) 2004 by Henrique de Moraes Holschuh
This is free software; see the source for copying conditions.  There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

rngtest: starting FIPS tests...
rngtest: bits received from input: 20000032
rngtest: FIPS 140-2 successes: 0
rngtest: FIPS 140-2 failures: 1000
rngtest: FIPS 140-2(2001-10-10) Monobit: 2
rngtest: FIPS 140-2(2001-10-10) Poker: 1000
rngtest: FIPS 140-2(2001-10-10) Runs: 1000
rngtest: FIPS 140-2(2001-10-10) Long run: 30
rngtest: FIPS 140-2(2001-10-10) Continuous run: 0
rngtest: input channel speed: (min=37.253; avg=320.827; max=635.783)Mibits/s
rngtest: FIPS tests speed: (min=12.141; avg=15.034; max=16.428)Mibits/s
rngtest: Program run time: 1336176 microseconds
cat: write error: Broken pipe

---
v5: remove reset_control_rearm().
v4: add reset_control_rearm().
v3: no changes.
v2: no changes.

 drivers/char/hw_random/bcm2835-rng.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

index be5be395b341..e7dd457e9b22 100644
@@ -13,6 +13,7 @@
 #include <linux/platform_device.h>
 #include <linux/printk.h>
 #include <linux/clk.h>
+#include <linux/reset.h>
 
 #define RNG_CTRL	0x0
 #define RNG_STATUS	0x4

@@ -32,6 +33,7 @@ struct bcm2835_rng_priv {
 	void __iomem *base;
 	bool mask_interrupts;
 	struct clk *clk;
+	struct reset_control *reset;
 };
 
 static inline struct bcm2835_rng_priv *to_rng_priv(struct hwrng *rng)

@@ -92,6 +94,10 @@ static int bcm2835_rng_init(struct hwrng *rng)
 	if (ret)
 		return ret;
 
+	ret = reset_control_reset(priv->reset);
+	if (ret)
+		return ret;
+
 	if (priv->mask_interrupts) {
 		/* mask the interrupt */
 		val = rng_readl(priv, RNG_INT_MASK);

@@ -156,6 +162,10 @@ static int bcm2835_rng_probe(struct platform_device *pdev)
 	if (IS_ERR(priv->clk))
 		return PTR_ERR(priv->clk);
 
+	priv->reset = devm_reset_control_get_optional_exclusive(dev, NULL);
+	if (IS_ERR(priv->reset))
+		return PTR_ERR(priv->reset);
+
 	priv->rng.name = pdev->name;
 	priv->rng.init = bcm2835_rng_init;
 	priv->rng.read = bcm2835_rng_read;

2.20.1

regards
Philipp

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