diff options
Diffstat (limited to 'drivers/char/hw_random/msm-rng.c')
| -rw-r--r-- | drivers/char/hw_random/msm-rng.c | 187 |
1 files changed, 187 insertions, 0 deletions
diff --git a/drivers/char/hw_random/msm-rng.c b/drivers/char/hw_random/msm-rng.c new file mode 100644 index 000000000..96fb98640 --- /dev/null +++ b/drivers/char/hw_random/msm-rng.c @@ -0,0 +1,187 @@ +/* + * Copyright (c) 2011-2013, The Linux Foundation. All rights reserved. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 and + * only version 2 as published by the Free Software Foundation. + * + * This program is distributed in the hope that 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/clk.h> +#include <linux/err.h> +#include <linux/hw_random.h> +#include <linux/io.h> +#include <linux/module.h> +#include <linux/of.h> +#include <linux/platform_device.h> + +/* Device specific register offsets */ +#define PRNG_DATA_OUT 0x0000 +#define PRNG_STATUS 0x0004 +#define PRNG_LFSR_CFG 0x0100 +#define PRNG_CONFIG 0x0104 + +/* Device specific register masks and config values */ +#define PRNG_LFSR_CFG_MASK 0x0000ffff +#define PRNG_LFSR_CFG_CLOCKS 0x0000dddd +#define PRNG_CONFIG_HW_ENABLE BIT(1) +#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; + struct hwrng hwrng; +}; + +#define to_msm_rng(p) container_of(p, struct msm_rng, hwrng) + +static int msm_rng_enable(struct hwrng *hwrng, int enable) +{ + struct msm_rng *rng = to_msm_rng(hwrng); + 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; + + 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_HW_ENABLE; + writel(val, rng->base + PRNG_CONFIG); + } else { + val = readl_relaxed(rng->base + PRNG_CONFIG); + val &= ~PRNG_CONFIG_HW_ENABLE; + writel(val, rng->base + PRNG_CONFIG); + } + +already_enabled: + clk_disable_unprepare(rng->clk); + return 0; +} + +static int msm_rng_read(struct hwrng *hwrng, void *data, size_t max, bool wait) +{ + struct msm_rng *rng = to_msm_rng(hwrng); + size_t currsize = 0; + u32 *retdata = data; + size_t maxsize; + int ret; + u32 val; + + /* calculate max size bytes to transfer back to caller */ + maxsize = min_t(size_t, MAX_HW_FIFO_SIZE, max); + + /* no room for word data */ + if (maxsize < WORD_SZ) + return 0; + + ret = clk_prepare_enable(rng->clk); + if (ret) + return ret; + + /* read random data from hardware */ + do { + val = readl_relaxed(rng->base + PRNG_STATUS); + if (!(val & PRNG_STATUS_DATA_AVAIL)) + break; + + val = readl_relaxed(rng->base + PRNG_DATA_OUT); + if (!val) + break; + + *retdata++ = val; + currsize += WORD_SZ; + + /* make sure we stay on 32bit boundary */ + if ((maxsize - currsize) < WORD_SZ) + break; + } while (currsize < maxsize); + + clk_disable_unprepare(rng->clk); + + return currsize; +} + +static int msm_rng_init(struct hwrng *hwrng) +{ + return msm_rng_enable(hwrng, 1); +} + +static void msm_rng_cleanup(struct hwrng *hwrng) +{ + msm_rng_enable(hwrng, 0); +} + +static int msm_rng_probe(struct platform_device *pdev) +{ + struct resource *res; + struct msm_rng *rng; + int ret; + + rng = devm_kzalloc(&pdev->dev, sizeof(*rng), GFP_KERNEL); + if (!rng) + return -ENOMEM; + + platform_set_drvdata(pdev, rng); + + 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->clk = devm_clk_get(&pdev->dev, "core"); + if (IS_ERR(rng->clk)) + return PTR_ERR(rng->clk); + + rng->hwrng.name = KBUILD_MODNAME, + rng->hwrng.init = msm_rng_init, + rng->hwrng.cleanup = msm_rng_cleanup, + rng->hwrng.read = msm_rng_read, + + ret = devm_hwrng_register(&pdev->dev, &rng->hwrng); + if (ret) { + dev_err(&pdev->dev, "failed to register hwrng\n"); + return ret; + } + + return 0; +} + +static const struct of_device_id msm_rng_of_match[] = { + { .compatible = "qcom,prng", }, + {} +}; +MODULE_DEVICE_TABLE(of, msm_rng_of_match); + +static struct platform_driver msm_rng_driver = { + .probe = msm_rng_probe, + .driver = { + .name = KBUILD_MODNAME, + .of_match_table = of_match_ptr(msm_rng_of_match), + } +}; +module_platform_driver(msm_rng_driver); + +MODULE_ALIAS("platform:" KBUILD_MODNAME); +MODULE_AUTHOR("The Linux Foundation"); +MODULE_DESCRIPTION("Qualcomm MSM random number generator driver"); +MODULE_LICENSE("GPL v2"); |