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

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Date:	Thu, 03 Oct 2013 12:25:37 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Stanimir Varbanov <svarbanov@...sol.com>
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

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.

> +#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.

> +
> +	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");


-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation

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