linux-kernel - Re: [PATCH 2/2] hwrng: msm: Add PRNG support for MSM SoC's

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Date:	Fri, 04 Oct 2013 19:31:10 +0300
From:	Stanimir Varbanov <svarbanov@...sol.com>
To:	Stephen Boyd <sboyd@...eaurora.org>
CC:	Rob Herring <rob.herring@...xeda.com>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Stephen Warren <swarren@...dotorg.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Matt Mackall <mpm@...enic.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	linux-kernel@...r.kernel.org, Rob Landley <rob@...dley.net>,
	devicetree@...r.kernel.org, linux-doc@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 2/2] hwrng: msm: Add PRNG support for MSM SoC's

Hi Stephen,

Thanks for the quick review!

On 10/03/2013 10:25 PM, Stephen Boyd wrote:
> On 10/03/13 07:52, Stanimir Varbanov wrote:
>> +#define PRNG_CONFIG_MASK	0x00000002
>> +#define PRNG_CONFIG_HW_ENABLE	BIT(1)
> 
> These two are the same so please drop the PRNG_CONFIG_MASK define and
> just use the PRNG_CONFIG_HW_ENABLE define.
> 

OK I will drop the mask and rework the code related to it.

>> +#define PRNG_STATUS_DATA_AVAIL	BIT(0)
>> +
>> +#define MAX_HW_FIFO_DEPTH	16
>> +#define MAX_HW_FIFO_SIZE	(MAX_HW_FIFO_DEPTH * 4)
>> +#define WORD_SZ			4
>> +
>> +struct msm_rng {
>> +	void __iomem *base;
>> +	struct clk *clk;
>> +};
>> +
>> +static int msm_rng_enable(struct msm_rng *rng, int enable)
>> +{
>> +	u32 val;
>> +	int ret;
>> +
>> +	ret = clk_prepare_enable(rng->clk);
>> +	if (ret)
>> +		return ret;
>> +
>> +	if (enable) {
>> +		/* Enable PRNG only if it is not already enabled */
>> +		val = readl_relaxed(rng->base + PRNG_CONFIG);
>> +		if (val & PRNG_CONFIG_HW_ENABLE)
>> +			goto already_enabled;
>> +
>> +		/* PRNG is not enabled */
>> +		val = readl_relaxed(rng->base + PRNG_LFSR_CFG);
>> +		val &= ~PRNG_LFSR_CFG_MASK;
>> +		val |= PRNG_LFSR_CFG_CLOCKS;
>> +		writel(val, rng->base + PRNG_LFSR_CFG);
>> +
>> +		val = readl_relaxed(rng->base + PRNG_CONFIG);
>> +		val &= ~PRNG_CONFIG_MASK;
>> +		val |= PRNG_CONFIG_HW_ENABLE;
>> +		writel(val, rng->base + PRNG_CONFIG);
> 
> This could just be
> 
> 		val = readl_relaxed(rng->base + PRNG_CONFIG);
> 		val |= PRNG_CONFIG_HW_ENABLE;
> 		writel(val, rng->base + PRNG_CONFIG);
> 
> 
>> +	} else {
>> +		val = readl_relaxed(rng->base + PRNG_CONFIG);
>> +		val &= ~PRNG_CONFIG_MASK;
>> +		writel(val, rng->base + PRNG_CONFIG);
>> +	}
>> +
>> +already_enabled:
>> +	clk_disable_unprepare(rng->clk);
>> +	return 0;
>> +}
>> +
> [...]
>> +static int msm_rng_probe(struct platform_device *pdev)
>> +{
>> +	struct msm_rng *rng;
>> +	struct device_node *np;
>> +	struct resource res;
>> +	int ret;
>> +
>> +	np = of_node_get(pdev->dev.of_node);
>> +	if (!np)
>> +		return -ENODEV;
> 
> This is unnecessary.

I used this call because CONFIG_OF_DYNAMIC could be enabled at some
time. Isn't that possible? I saw that of_node_get|put is used in .probe
on few places in drivers.

> 
>> +
>> +	rng = devm_kzalloc(&pdev->dev, sizeof(*rng), GFP_KERNEL);
>> +	if (!rng) {
>> +		ret = -ENOMEM;
>> +		goto err_exit;
>> +	}
>> +
>> +	ret = of_address_to_resource(np, 0, &res);
>> +	if (ret)
>> +		goto err_exit;
> 
> We should just do
> 
>   res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>   rng->base = devm_ioremap_resource(&pdev->dev, res);
>   if (IS_ERR(rng->base))
>             return PTR_ERR(rng->base);
> 
>> +
>> +	rng->base = devm_ioremap_resource(&pdev->dev, &res);
>> +	if (IS_ERR(rng->base)) {
>> +		ret = PTR_ERR(rng->base);
>> +		goto err_exit;
>> +	}
>> +
>> +	rng->clk = devm_clk_get(&pdev->dev, "prng");
>> +	if (IS_ERR(rng->clk)) {
>> +		ret = PTR_ERR(rng->clk);
>> +		goto err_exit;
>> +	}
>> +
>> +	msm_rng_ops.priv = (unsigned long) rng;
>> +	ret = hwrng_register(&msm_rng_ops);
>> +	if (ret)
>> +		dev_err(&pdev->dev, "failed to register hwrng\n");
>> +
>> +err_exit:
> 
> Doing all that should make this goto exit path unnecessary.
> 
>> +	of_node_put(np);
>> +	return ret;
>> +}
>> +
>> +static int msm_rng_remove(struct platform_device *pdev)
>> +{
>> +	hwrng_unregister(&msm_rng_ops);
>> +	return 0;
>> +}
>> +
>> +static struct of_device_id msm_rng_of_match[] = {
> 
> const?
> 
>> +	{ .compatible = "qcom,prng", },
>> +	{}
>> +};
>> +MODULE_DEVICE_TABLE(of, msm_rng_of_match);
>> +
>> +static struct platform_driver msm_rng_driver = {
>> +	.probe = msm_rng_probe,
>> +	.remove = msm_rng_remove,
>> +	.driver = {
>> +		.name = KBUILD_MODNAME,
>> +		.owner = THIS_MODULE,
>> +		.of_match_table = of_match_ptr(msm_rng_of_match),
>> +	}
>> +};
>> +module_platform_driver(msm_rng_driver);
>> +
>> +MODULE_AUTHOR("The Linux Foundation");
>> +MODULE_DESCRIPTION("Qualcomm MSM random number generator driver");
>> +MODULE_LICENSE("GPL v2");
> 
> 

regards,
Stan

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