linux-kernel - Re: [PATCH 07/12] hwrng: bcm2835-rng: Manage an optional clock

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Date:   Sat, 4 Nov 2017 14:50:54 +0100 (CET)
From:   Stefan Wahren <stefan.wahren@...e.com>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Krzysztof Kozlowski <krzk@...nel.org>, Ray Jui <rjui@...adcom.com>,
        Eric Anholt <eric@...olt.net>,
        Rob Herring <robh+dt@...nel.org>,
        Steffen Trumtrar <s.trumtrar@...gutronix.de>,
        Harald Freudenberger <freude@...ux.vnet.ibm.com>,
        Russell King <rmk+kernel@...linux.org.uk>,
        "moderated list:BROADCOM BCM2835 ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        PrasannaKumar Muralidharan <prasannatsmkumar@...il.com>,
        Scott Branden <sbranden@...adcom.com>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@...r.kernel.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Martin Kaiser <martin@...ser.cx>,
        Matt Mackall <mpm@...enic.com>,
        "maintainer:BROADCOM BCM281XX/BCM11XXX/BCM216XX ARM ARCHITE..." 
        <bcm-kernel-feedback-list@...adcom.com>,
        Mark Rutland <mark.rutland@....com>,
        "moderated list:BROADCOM BCM2835 ARM ARCHITECTURE" 
        <linux-rpi-kernel@...ts.infradead.org>,
        linux-kernel@...r.kernel.org, Sean Wang <sean.wang@...iatek.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH 07/12] hwrng: bcm2835-rng: Manage an optional clock

Hi Florian,

> Florian Fainelli <f.fainelli@...il.com> hat am 2. November 2017 um 02:04 geschrieben:
> 
> 
> One of the last steps before bcm63xx-rng can be eliminated is to manage
> a clock during hwrng::init and hwrng::cleanup, so fetch it in the probe
> function, and manage it during these two steps when valid.
> 
> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
> ---
>  drivers/char/hw_random/bcm2835-rng.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/char/hw_random/bcm2835-rng.c b/drivers/char/hw_random/bcm2835-rng.c
> index ed20e0b6b7ae..35928efb52e7 100644
> --- a/drivers/char/hw_random/bcm2835-rng.c
> +++ b/drivers/char/hw_random/bcm2835-rng.c
> @@ -15,6 +15,7 @@
>  #include <linux/of_platform.h>
>  #include <linux/platform_device.h>
>  #include <linux/printk.h>
> +#include <linux/clk.h>
>  
>  #define RNG_CTRL	0x0
>  #define RNG_STATUS	0x4
> @@ -33,6 +34,7 @@ struct bcm2835_rng_priv {
>  	struct hwrng rng;
>  	void __iomem *base;
>  	bool mask_interrupts;
> +	struct clk *clk;
>  };
>  
>  static inline struct bcm2835_rng_priv *to_rng_priv(struct hwrng *rng)
> @@ -67,6 +69,11 @@ static int bcm2835_rng_init(struct hwrng *rng)
>  {
>  	struct bcm2835_rng_priv *priv = to_rng_priv(rng);
>  	u32 val;
> +	int ret;
> +
> +	ret = clk_prepare_enable(priv->clk);
> +	if (ret)
> +		return ret;
>  
>  	if (priv->mask_interrupts) {
>  		/* mask the interrupt */
> @@ -88,6 +95,8 @@ static void bcm2835_rng_cleanup(struct hwrng *rng)
>  
>  	/* disable rng hardware */
>  	__raw_writel(0, priv->base + RNG_CTRL);
> +
> +	clk_disable_unprepare(priv->clk);
>  }
>  
>  struct bcm2835_rng_of_data {
> @@ -130,6 +139,11 @@ static int bcm2835_rng_probe(struct platform_device *pdev)
>  		return PTR_ERR(priv->base);
>  	}
>  
> +	/* Clock is optional on most platforms */
> +	priv->clk = devm_clk_get(dev, NULL);
> +	if (IS_ERR(priv->clk))
> +		priv->clk = NULL;

at least in case of EPROBE_DEFERED this isn't the expected behavior. Maybe we should better trigger on non-existing clock?

> +
>  	priv->rng.name = "bcm2835-rng";
>  	priv->rng.init = bcm2835_rng_init;
>  	priv->rng.read = bcm2835_rng_read;
> -- 
> 2.9.3
>