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Date: Wed, 20 Jun 2012 17:47:35 -0700
From: Stephen Boyd <sboyd@...eaurora.org>
To: Jonghwa Lee <jonghwa3.lee@...sung.com>
CC: linux-kernel@...r.kernel.org, Matt Mackall <mpm@...enic.com>,
Herbert Xu <herbert@...dor.apana.org.au>,
Nicolas Ferre <nicolas.ferre@...el.com>,
Julia Lawall <Julia.Lawall@...6.fr>,
Jamie Iles <jamie@...ieiles.com>,
Kyungmin Park <kyungmin.park@...sung.com>
Subject: Re: [PATCH] Exynos : Add support for Exynos random number generator
On 06/20/12 01:22, Jonghwa Lee wrote:
> diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
> index f45dad3..8220026 100644
> --- a/drivers/char/hw_random/Kconfig
> +++ b/drivers/char/hw_random/Kconfig
> @@ -263,3 +263,15 @@ config HW_RANDOM_PSERIES
> module will be called pseries-rng.
>
> If unsure, say Y.
> +
> +config HW_RANDOM_EXYNOS
> + tristate "EXYNOS Random Number Generator support"
> + depends on HW_RANDOM && ARCH_EXYNOS4
I don't see how this actually depends on ARCH_EXYNOS4 to be compiled. I
obviously wouldn't want to compile in this driver if I didn't have the
hardware but the driver seems generic enough to be compiled anywhere
(e.g. in an x86 allmodconfig). I suppose you need to add HAS_IOMEM though.
> + ---help---
> + This driver provides kernel-side support for the Random Number
> + Generator hardware found on EXYNOS SOCs.
Why is 'random number generator' capitalized?
> diff --git a/drivers/char/hw_random/exynos-rng.c b/drivers/char/hw_random/exynos-rng.c
> new file mode 100644
> index 0000000..b58a28b
> --- /dev/null
> +++ b/drivers/char/hw_random/exynos-rng.c
> @@ -0,0 +1,204 @@
[snip]
> +#include <linux/clk.h>
> +#include <linux/pm_runtime.h>
> +
> +#define EXYNOS_PRNG_STATUS_OFFSET 0x10
> +#define EXYNOS_PRNG_SEED_OFFSET 0x140
> +#define EXYNOS_PRNG_OUT1_OFFSET 0x160
> +#define SEED_SETTING_DONE BIT(1)
> +#define PRNG_START 0x18
> +#define PRNG_DONE BIT(5)
Please consistently use tabs or spaces here between the '#define' and
the name.
> +
> +struct exynos_rng {
> + struct device *dev;
> + struct hwrng rng;
> + void __iomem *mem;
> + struct clk *clk;
> +};
> +
> +static u32 exynos_rng_readl(void __iomem *base, u32 offset)
> +{
> + return __raw_readl(base + offset);
> +}
There seems to be a tab here? Also, why don't these read/write functions
take the exynos_rng struct so that you don't have to pass the base
pointer. That would make these functions more useful than just being a
wrapper around __raw_{readl,writel}()
u32 exynos_rng_readl(struct exynos_rng *rng, u32 offset)
void exynos_rng_writel(struct exynos_rng *rng, u32 val, u32 offset)
> +
> +static void exynos_rng_writel(u32 val, void __iomem *base, u32 offset)
> +{
> + __raw_writel(val, base + offset);
> +}
> +
> +static int exynos_init(struct hwrng *rng)
> +{
> + struct exynos_rng *exynos_rng = container_of(rng,
> + struct exynos_rng, rng);
> + int i;
> + int ret = 0;
> + u32 PRND_SEED[5];
> +
> + pm_runtime_put_noidle(exynos_rng->dev);
> + pm_runtime_get_sync(exynos_rng->dev);
This looks very odd. Why are you calling pm_runtime_put_noidle()?
> +
> + for (i = 0 ; i < 5 ; i++) {
> + PRND_SEED[i] = i;
> + exynos_rng_writel(PRND_SEED[i], exynos_rng->mem,
> + EXYNOS_PRNG_SEED_OFFSET + 4*i);
> + }
Is this just writing 0,1,2,3,4 to registers? What is the array for?
> +
> + if (!(exynos_rng_readl(exynos_rng->mem, EXYNOS_PRNG_STATUS_OFFSET)
> + & SEED_SETTING_DONE))
> + ret = -EIO;
> +
> + pm_runtime_put(exynos_rng->dev);
> + pm_runtime_get_noresume(exynos_rng->dev);
> +
> + return ret;
> +}
> +
> +static int exynos_read(struct hwrng *rng, void *buf,
> + size_t max, bool wait)
> +{
> + struct exynos_rng *exynos_rng = container_of(rng,
> + struct exynos_rng, rng);
> + u32 *data = buf;
> + u32 status = 0;
Drop this assignment here.
> +
> + pm_runtime_get_sync(exynos_rng->dev);
> + exynos_rng_writel(PRNG_START, exynos_rng->mem, 0);
> +
> + while (!status) {
> + status = exynos_rng_readl(exynos_rng->mem,
> + EXYNOS_PRNG_STATUS_OFFSET);
> + status &= PRNG_DONE;
> + }
And make this into a do while with a cpu_relax() thrown in there.
> +
> + exynos_rng_writel(PRNG_DONE, exynos_rng->mem,
> + EXYNOS_PRNG_STATUS_OFFSET);
> +
> + *data = exynos_rng_readl(exynos_rng->mem,
> + EXYNOS_PRNG_OUT1_OFFSET);
> +
> + pm_runtime_put(exynos_rng->dev);
> + return 4;
> +}
> +
> +static int __init exynos_rng_probe(struct platform_device *pdev)
__devinit
> +{
> + int ret;
> + struct exynos_rng *exynos_rng;
> + struct resource *res;
> +
> + exynos_rng = devm_kzalloc(&pdev->dev, sizeof(struct exynos_rng),
> + GFP_KERNEL);
> + if (!exynos_rng)
> + return -ENOMEM;
> +
> + exynos_rng->dev = &pdev->dev;
> + exynos_rng->rng.name = "exynos";
> + exynos_rng->rng.init = exynos_init;
> + exynos_rng->rng.read = exynos_read;
> + exynos_rng->clk = clk_get(NULL, "secss");
Can you please pass &pdev->dev to clk_get()?
> + if (!exynos_rng->clk) {
NULL is a valid clock. Please check for IS_ERR() only. Also you may want
to use devm_clk_get().
> + dev_err(&pdev->dev, "Couldn't get clock.\n");
> + return -ENOENT;
> + }
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + if (!res) {
> + clk_put(exynos_rng->clk);
> + return -ENODEV;
> + }
> +
> + exynos_rng->mem = devm_ioremap(&pdev->dev, res->start,
> + resource_size(res));
It might be a good idea to use devm_request_and_ioremap() here instead.
> + if (!exynos_rng->mem) {
> + dev_err(&pdev->dev, "Ioremap failed.\n");
> + return -EBUSY;
> + }
> +
> + platform_set_drvdata(pdev, exynos_rng);
> +
> + pm_runtime_enable(&pdev->dev);
> + pm_runtime_irq_safe(&pdev->dev);
It doesn't seem like you need to run runtime PM calls in irq context.
Why is this here?
> +
> + ret = hwrng_register(&exynos_rng->rng);
> + if (ret) {
> + clk_put(exynos_rng->clk);
> + return ret;
> + }
> +
> + return 0;
> +}
> +
> +static int __exit exynos_rng_remove(struct platform_device *pdev)
__devexit
> +{
> + struct exynos_rng *exynos_rng = platform_get_drvdata(pdev);
> +
> + hwrng_unregister(&exynos_rng->rng);
> + clk_put(exynos_rng->clk);
> + return 0;
> +}
> +
> +static int exynos_rng_runtime_suspend(struct device *dev)
> +{
> + struct platform_device *pdev = to_platform_device(dev);
> + struct exynos_rng *exynos_rng = platform_get_drvdata(pdev);
> +
> + clk_disable(exynos_rng->clk);
> + return 0;
> +}
> +
> +static int exynos_rng_runtime_resume(struct device *dev)
> +{
> + struct platform_device *pdev = to_platform_device(dev);
> + struct exynos_rng *exynos_rng = platform_get_drvdata(pdev);
> +
> + clk_enable(exynos_rng->clk);
Please use clk_prepare_enable()/clk_disable_unprepare() so we don't have
to convert this driver later.
> +
> +static const struct dev_pm_ops exynos_rng_pm_ops = {
> + .runtime_suspend = exynos_rng_runtime_suspend,
> + .runtime_resume = exynos_rng_runtime_resume,
> +};
You should use something like UNIVERSAL_DEV_PM_OPS here so that you can
#ifdef CONFIG_PM the runtime suspend/resume functions. If CONFIG_PM=n
does this driver work? I wonder if the clocks are assumed to be on in
that case?
> +
> +static struct platform_driver exynos_rng_driver = {
> + .driver = {
> + .name = "exynos-rng",
> + .owner = THIS_MODULE,
> + .pm = &exynos_rng_pm_ops,
> + },
> + .probe = exynos_rng_probe,
> + .remove = exynos_rng_remove,
__devexit_p()
--
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
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