diff mbox series

[v4,2/2] hwrng: bcm2835: add reset support

Message ID 20210224082230.29015-3-noltari@gmail.com (mailing list archive)
State New, archived
Headers show
Series hwrng: bcm2835: add reset support | expand

Commit Message

Álvaro Fernández Rojas Feb. 24, 2021, 8:22 a.m. UTC 
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

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
---
 v4: add reset_control_rearm().
 v3: no changes.
 v2: no changes.

 drivers/char/hw_random/bcm2835-rng.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

Comments

Philipp Zabel March 3, 2021, 1:52 p.m. UTC | #1 
Hi Álvaro,

On Wed, 2021-02-24 at 09:22 +0100, Álvaro Fernández Rojas wrote:
[...]
> @@ -115,6 +121,8 @@ static void bcm2835_rng_cleanup(struct hwrng *rng)
>  	/* disable rng hardware */
>  	rng_writel(priv, 0, RNG_CTRL);
>  
> +	reset_control_rearm(priv->reset);
> +
>  	if (!IS_ERR(priv->clk))
>  		clk_disable_unprepare(priv->clk);
>  }
> @@ -159,6 +167,10 @@ static int bcm2835_rng_probe(struct platform_device *pdev)
>  	if (PTR_ERR(priv->clk) == -EPROBE_DEFER)
>  		return -EPROBE_DEFER;
>  
> +	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;

That doesn't seem right. reset_control_rearm() doesn't do anything if
the reset control is exclusive. Either the reset control should be
requested as shared, or the _rearm should be removed.

regards
Philipp
Álvaro Fernández Rojas March 3, 2021, 2:06 p.m. UTC | #2 
Hi Philipp,

> El 3 mar 2021, a las 14:52, Philipp Zabel <p.zabel@pengutronix.de> escribió:
> 
> Hi Álvaro,
> 
> On Wed, 2021-02-24 at 09:22 +0100, Álvaro Fernández Rojas wrote:
> [...]
>> @@ -115,6 +121,8 @@ static void bcm2835_rng_cleanup(struct hwrng *rng)
>> 	/* disable rng hardware */
>> 	rng_writel(priv, 0, RNG_CTRL);
>> 
>> +	reset_control_rearm(priv->reset);
>> +
>> 	if (!IS_ERR(priv->clk))
>> 		clk_disable_unprepare(priv->clk);
>> }
>> @@ -159,6 +167,10 @@ static int bcm2835_rng_probe(struct platform_device *pdev)
>> 	if (PTR_ERR(priv->clk) == -EPROBE_DEFER)
>> 		return -EPROBE_DEFER;
>> 
>> +	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;
> 
> That doesn't seem right. reset_control_rearm() doesn't do anything if
> the reset control is exclusive. Either the reset control should be
> requested as shared, or the _rearm should be removed.

In only added reset_control_rearm() because Florian requested it…
I think it’s not needed, so we can use v3, since it was the only change between v3 and v4...

> 
> regards
> Philipp

Best regards,
Álvaro.
Florian Fainelli March 3, 2021, 7:16 p.m. UTC | #3 
On 3/3/21 6:06 AM, Álvaro Fernández Rojas wrote:
> Hi Philipp,
> 
>> El 3 mar 2021, a las 14:52, Philipp Zabel <p.zabel@pengutronix.de> escribió:
>>
>> Hi Álvaro,
>>
>> On Wed, 2021-02-24 at 09:22 +0100, Álvaro Fernández Rojas wrote:
>> [...]
>>> @@ -115,6 +121,8 @@ static void bcm2835_rng_cleanup(struct hwrng *rng)
>>> 	/* disable rng hardware */
>>> 	rng_writel(priv, 0, RNG_CTRL);
>>>
>>> +	reset_control_rearm(priv->reset);
>>> +
>>> 	if (!IS_ERR(priv->clk))
>>> 		clk_disable_unprepare(priv->clk);
>>> }
>>> @@ -159,6 +167,10 @@ static int bcm2835_rng_probe(struct platform_device *pdev)
>>> 	if (PTR_ERR(priv->clk) == -EPROBE_DEFER)
>>> 		return -EPROBE_DEFER;
>>>
>>> +	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;
>>
>> That doesn't seem right. reset_control_rearm() doesn't do anything if
>> the reset control is exclusive. Either the reset control should be
>> requested as shared, or the _rearm should be removed.
> 
> In only added reset_control_rearm() because Florian requested it…
> I think it’s not needed, so we can use v3, since it was the only change between v3 and v4...

Not the first time I am confused by the reset API not sure if I will
ever get it one day, so apologies for suggesting something incorrect here.
diff mbox series

Patch

diff --git a/drivers/char/hw_random/bcm2835-rng.c b/drivers/char/hw_random/bcm2835-rng.c
index 1a7c43b43c6b..92658edaff22 100644
--- a/drivers/char/hw_random/bcm2835-rng.c
+++ b/drivers/char/hw_random/bcm2835-rng.c
@@ -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)
@@ -94,6 +96,10 @@  static int bcm2835_rng_init(struct hwrng *rng)
 			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);
@@ -115,6 +121,8 @@  static void bcm2835_rng_cleanup(struct hwrng *rng)
 	/* disable rng hardware */
 	rng_writel(priv, 0, RNG_CTRL);
 
+	reset_control_rearm(priv->reset);
+
 	if (!IS_ERR(priv->clk))
 		clk_disable_unprepare(priv->clk);
 }
@@ -159,6 +167,10 @@  static int bcm2835_rng_probe(struct platform_device *pdev)
 	if (PTR_ERR(priv->clk) == -EPROBE_DEFER)
 		return -EPROBE_DEFER;
 
+	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;