From: Daniel Thompson Subject: Re: [PATCH 2/2] rng: pic32-rng: Add PIC32 RNG hardware driver Date: Wed, 3 Feb 2016 11:22:53 +0000 Message-ID: <56B1E30D.8090509@linaro.org> References: <1454366511-10640-1-git-send-email-joshua.henderson@microchip.com> <1454366511-10640-2-git-send-email-joshua.henderson@microchip.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-mips@linux-mips.org, Purna Chandra Mandal , Matt Mackall , Herbert Xu , Kieran Bingham , Lee Jones , Pankaj Dev , Scott Branden , Ray Jui , linux-crypto@vger.kernel.org To: Joshua Henderson , linux-kernel@vger.kernel.org Return-path: Received: from mail-wm0-f54.google.com ([74.125.82.54]:34414 "EHLO mail-wm0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751305AbcBCLW4 (ORCPT ); Wed, 3 Feb 2016 06:22:56 -0500 Received: by mail-wm0-f54.google.com with SMTP id 128so160357784wmz.1 for ; Wed, 03 Feb 2016 03:22:56 -0800 (PST) In-Reply-To: <1454366511-10640-2-git-send-email-joshua.henderson@microchip.com> Sender: linux-crypto-owner@vger.kernel.org List-ID: 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 > Signed-off-by: Purna Chandra Mandal > --- > 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 > + * 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 > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > +#include > + > +#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 "); > +MODULE_DESCRIPTION("Microchip PIC32 RNG Driver"); >