On 01/02/16 22:41, Joshua Henderson wrote:
Add support for the hardware pseudo and true random number generator peripheral found on PIC32. Signed-off-by: Joshua Henderson <joshua.henderson@xxxxxxxxxxxxx> Signed-off-by: Purna Chandra Mandal <purna.mandal@xxxxxxxxxxxxx> --- drivers/char/hw_random/Kconfig | 13 +++ drivers/char/hw_random/Makefile | 1 + drivers/char/hw_random/pic32-rng.c | 152 ++++++++++++++++++++++++++++++++++++ 3 files changed, 166 insertions(+) create mode 100644 drivers/char/hw_random/pic32-rng.c diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig index dbf2271..3ab0c46 100644 --- a/drivers/char/hw_random/Kconfig +++ b/drivers/char/hw_random/Kconfig @@ -381,6 +381,19 @@ config HW_RANDOM_STM32 If unsure, say N. +config HW_RANDOM_PIC32 + tristate "Microchip PIC32 Random Number Generator support" + depends on HW_RANDOM && MACH_PIC32 + default y + ---help--- + This driver provides kernel-side support for the Random Number + Generator hardware found on a PIC32. + + To compile this driver as a module, choose M here. the + module will be called pic32-rng. + + If unsure, say Y. + endif # HW_RANDOM config UML_RANDOM diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile index 5ad3976..f5a6fa7 100644 --- a/drivers/char/hw_random/Makefile +++ b/drivers/char/hw_random/Makefile @@ -33,3 +33,4 @@ obj-$(CONFIG_HW_RANDOM_MSM) += msm-rng.o obj-$(CONFIG_HW_RANDOM_ST) += st-rng.o obj-$(CONFIG_HW_RANDOM_XGENE) += xgene-rng.o obj-$(CONFIG_HW_RANDOM_STM32) += stm32-rng.o +obj-$(CONFIG_HW_RANDOM_PIC32) += pic32-rng.o diff --git a/drivers/char/hw_random/pic32-rng.c b/drivers/char/hw_random/pic32-rng.c new file mode 100644 index 0000000..d2f32c4 --- /dev/null +++ b/drivers/char/hw_random/pic32-rng.c @@ -0,0 +1,152 @@ +/* + * PIC32 RNG driver + * + * Joshua Henderson <joshua.henderson@xxxxxxxxxxxxx> + * Copyright (C) 2016 Microchip Technology Inc. All rights reserved. + * + * This program is free software; you can distribute it and/or modify it + * under the terms of the GNU General Public License (Version 2) as + * published by the Free Software Foundation. + * + * This program is distributed in the hope it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + * for more details. + */ + +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/delay.h> +#include <linux/slab.h> +#include <linux/err.h> +#include <linux/io.h> +#include <linux/hw_random.h> +#include <linux/platform_device.h> +#include <linux/of.h> +#include <linux/of_device.h> +#include <linux/clk.h> +#include <linux/clkdev.h> + +#define RNGCON 0x04 +#define TRNGEN BIT(8) +#define PRNGEN BIT(9) +#define PRNGCONT BIT(10) +#define TRNGMOD BIT(11) +#define SEEDLOAD BIT(12) +#define RNGPOLY1 0x08 +#define RNGPOLY2 0x0C +#define RNGNUMGEN1 0x10 +#define RNGNUMGEN2 0x14 +#define RNGSEED1 0x18 +#define RNGSEED2 0x1C +#define RNGRCNT 0x20 +#define RCNT_MASK 0x7F + +struct pic32_rng { + void __iomem *base; + struct hwrng rng; + struct clk *clk; +}; + +static int pic32_rng_read(struct hwrng *rng, void *buf, size_t max, + bool wait) +{ + struct pic32_rng *prng = container_of(rng, struct pic32_rng, rng); + u64 *data = buf; + + *data = ((u64)readl(prng->base + RNGNUMGEN2) << 32) + + readl(prng->base + RNGNUMGEN1); + return 4; +}
I have a number of questions at this point (although #3 is by far the most important).
1. If the random number of 42-bit shouldn't this be return 5; ? 2. If you really do mean return 4; then why mess about with all the shifting. You can just read and discard the upper 32-bits. 3. Why are you using the PRNG at all? The PRNG is a simple LSFR and I don't think it ever gets reseeded at any point (meaning we get almost no useful entropy from it at all). Far better to read directly from the TRNG.
+ +static int pic32_rng_probe(struct platform_device *pdev) +{ + struct pic32_rng *prng; + struct resource *res; + u32 v, t; + int ret; + + prng = devm_kzalloc(&pdev->dev, sizeof(*prng), GFP_KERNEL); + if (!prng) + return -ENOMEM; + + res = platform_get_resource(pdev, IORESOURCE_MEM, 0); + prng->base = devm_ioremap_resource(&pdev->dev, res); + if (IS_ERR(prng->base)) + return PTR_ERR(prng->base); + + prng->clk = devm_clk_get(&pdev->dev, NULL); + if (IS_ERR(prng->clk)) + return PTR_ERR(prng->clk); + + clk_prepare_enable(prng->clk); + + /* enable TRNG in enhanced mode */ + v = readl(prng->base + RNGCON); + v &= ~(TRNGEN | PRNGEN | 0xff); + v |= TRNGMOD; + writel(v | TRNGEN, prng->base + RNGCON); + + /* wait for valid seed */ + usleep_range(100, 200); + t = readl(prng->base + RNGRCNT) & RCNT_MASK; + if (t < 0x2A) + dev_warn(&pdev->dev, "seed not generated.\n"); + + /* load initial seed */ + writel(v | SEEDLOAD, prng->base + RNGCON); + + /* load initial polynomial: 42bit poly */ + writel(0x00c00003, prng->base + RNGPOLY1); + writel(0x00000000, prng->base + RNGPOLY2); + + /* start PRNG to generate 42bit random */ + v |= 0x2A | PRNGCONT | PRNGEN; + writel(v, prng->base + RNGCON); + + prng->rng.name = pdev->name; + prng->rng.read = pic32_rng_read; + + ret = hwrng_register(&prng->rng); + if (ret) + goto err_register; + + platform_set_drvdata(pdev, prng); + + return 0; + +err_register: + return ret;
Looks like we leak clock references on this error path.
+ +static int pic32_rng_remove(struct platform_device *pdev) +{ + struct pic32_rng *rng = platform_get_drvdata(pdev); + + hwrng_unregister(&rng->rng); + writel(0, rng->base + RNGCON); + clk_disable_unprepare(rng->clk); + return 0; +} + +static const struct of_device_id pic32_rng_of_match[] = { + { .compatible = "microchip,pic32mzda-rng", }, + { /* sentinel */ } +}; +MODULE_DEVICE_TABLE(of, pic32_rng_of_match); + +static struct platform_driver pic32_rng_driver = { + .probe = pic32_rng_probe, + .remove = pic32_rng_remove, + .driver = { + .name = "pic32-rng", + .owner = THIS_MODULE, + .of_match_table = of_match_ptr(pic32_rng_of_match), + }, +}; + +module_platform_driver(pic32_rng_driver); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Joshua Henderson <joshua.henderson@xxxxxxxxxxxxx>"); +MODULE_DESCRIPTION("Microchip PIC32 RNG Driver");
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