1c6a97c42SDaniel Thompson /* 2c6a97c42SDaniel Thompson * Copyright (c) 2015, Daniel Thompson 3c6a97c42SDaniel Thompson * 4c6a97c42SDaniel Thompson * This file is free software; you can redistribute it and/or 5c6a97c42SDaniel Thompson * modify it under the terms of the GNU General Public License 6c6a97c42SDaniel Thompson * as published by the Free Software Foundation; either version 2 7c6a97c42SDaniel Thompson * of the License, or (at your option) any later version. 8c6a97c42SDaniel Thompson * 9c6a97c42SDaniel Thompson * This file is distributed in the hope that it will be useful, 10c6a97c42SDaniel Thompson * but WITHOUT ANY WARRANTY; without even the implied warranty of 11c6a97c42SDaniel Thompson * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12c6a97c42SDaniel Thompson * GNU General Public License for more details. 13c6a97c42SDaniel Thompson */ 14c6a97c42SDaniel Thompson 15c6a97c42SDaniel Thompson #include <linux/clk.h> 16c6a97c42SDaniel Thompson #include <linux/delay.h> 17c6a97c42SDaniel Thompson #include <linux/hw_random.h> 18c6a97c42SDaniel Thompson #include <linux/io.h> 19c6a97c42SDaniel Thompson #include <linux/kernel.h> 20c6a97c42SDaniel Thompson #include <linux/module.h> 21c6a97c42SDaniel Thompson #include <linux/of_address.h> 22c6a97c42SDaniel Thompson #include <linux/of_platform.h> 23c6a97c42SDaniel Thompson #include <linux/pm_runtime.h> 24c6a97c42SDaniel Thompson #include <linux/slab.h> 25c6a97c42SDaniel Thompson 26c6a97c42SDaniel Thompson #define RNG_CR 0x00 27c6a97c42SDaniel Thompson #define RNG_CR_RNGEN BIT(2) 28c6a97c42SDaniel Thompson 29c6a97c42SDaniel Thompson #define RNG_SR 0x04 30c6a97c42SDaniel Thompson #define RNG_SR_SEIS BIT(6) 31c6a97c42SDaniel Thompson #define RNG_SR_CEIS BIT(5) 32c6a97c42SDaniel Thompson #define RNG_SR_DRDY BIT(0) 33c6a97c42SDaniel Thompson 34c6a97c42SDaniel Thompson #define RNG_DR 0x08 35c6a97c42SDaniel Thompson 36c6a97c42SDaniel Thompson /* 37c6a97c42SDaniel Thompson * It takes 40 cycles @ 48MHz to generate each random number (e.g. <1us). 38c6a97c42SDaniel Thompson * At the time of writing STM32 parts max out at ~200MHz meaning a timeout 39c6a97c42SDaniel Thompson * of 500 leaves us a very comfortable margin for error. The loop to which 40c6a97c42SDaniel Thompson * the timeout applies takes at least 4 instructions per iteration so the 41c6a97c42SDaniel Thompson * timeout is enough to take us up to multi-GHz parts! 42c6a97c42SDaniel Thompson */ 43c6a97c42SDaniel Thompson #define RNG_TIMEOUT 500 44c6a97c42SDaniel Thompson 45c6a97c42SDaniel Thompson struct stm32_rng_private { 46c6a97c42SDaniel Thompson struct hwrng rng; 47c6a97c42SDaniel Thompson void __iomem *base; 48c6a97c42SDaniel Thompson struct clk *clk; 49c6a97c42SDaniel Thompson }; 50c6a97c42SDaniel Thompson 51c6a97c42SDaniel Thompson static int stm32_rng_read(struct hwrng *rng, void *data, size_t max, bool wait) 52c6a97c42SDaniel Thompson { 53c6a97c42SDaniel Thompson struct stm32_rng_private *priv = 54c6a97c42SDaniel Thompson container_of(rng, struct stm32_rng_private, rng); 55c6a97c42SDaniel Thompson u32 sr; 56c6a97c42SDaniel Thompson int retval = 0; 57c6a97c42SDaniel Thompson 58c6a97c42SDaniel Thompson pm_runtime_get_sync((struct device *) priv->rng.priv); 59c6a97c42SDaniel Thompson 60c6a97c42SDaniel Thompson while (max > sizeof(u32)) { 61c6a97c42SDaniel Thompson sr = readl_relaxed(priv->base + RNG_SR); 62c6a97c42SDaniel Thompson if (!sr && wait) { 63c6a97c42SDaniel Thompson unsigned int timeout = RNG_TIMEOUT; 64c6a97c42SDaniel Thompson 65c6a97c42SDaniel Thompson do { 66c6a97c42SDaniel Thompson cpu_relax(); 67c6a97c42SDaniel Thompson sr = readl_relaxed(priv->base + RNG_SR); 68c6a97c42SDaniel Thompson } while (!sr && --timeout); 69c6a97c42SDaniel Thompson } 70c6a97c42SDaniel Thompson 71c6a97c42SDaniel Thompson /* If error detected or data not ready... */ 721ff69adfSMaxime Coquelin if (sr != RNG_SR_DRDY) { 731ff69adfSMaxime Coquelin if (WARN_ONCE(sr & (RNG_SR_SEIS | RNG_SR_CEIS), 741ff69adfSMaxime Coquelin "bad RNG status - %x\n", sr)) 751ff69adfSMaxime Coquelin writel_relaxed(0, priv->base + RNG_SR); 76c6a97c42SDaniel Thompson break; 771ff69adfSMaxime Coquelin } 78c6a97c42SDaniel Thompson 79c6a97c42SDaniel Thompson *(u32 *)data = readl_relaxed(priv->base + RNG_DR); 80c6a97c42SDaniel Thompson 81c6a97c42SDaniel Thompson retval += sizeof(u32); 82c6a97c42SDaniel Thompson data += sizeof(u32); 83c6a97c42SDaniel Thompson max -= sizeof(u32); 84c6a97c42SDaniel Thompson } 85c6a97c42SDaniel Thompson 86c6a97c42SDaniel Thompson pm_runtime_mark_last_busy((struct device *) priv->rng.priv); 87c6a97c42SDaniel Thompson pm_runtime_put_sync_autosuspend((struct device *) priv->rng.priv); 88c6a97c42SDaniel Thompson 89c6a97c42SDaniel Thompson return retval || !wait ? retval : -EIO; 90c6a97c42SDaniel Thompson } 91c6a97c42SDaniel Thompson 92c6a97c42SDaniel Thompson static int stm32_rng_init(struct hwrng *rng) 93c6a97c42SDaniel Thompson { 94c6a97c42SDaniel Thompson struct stm32_rng_private *priv = 95c6a97c42SDaniel Thompson container_of(rng, struct stm32_rng_private, rng); 96c6a97c42SDaniel Thompson int err; 97c6a97c42SDaniel Thompson 98c6a97c42SDaniel Thompson err = clk_prepare_enable(priv->clk); 99c6a97c42SDaniel Thompson if (err) 100c6a97c42SDaniel Thompson return err; 101c6a97c42SDaniel Thompson 102c6a97c42SDaniel Thompson writel_relaxed(RNG_CR_RNGEN, priv->base + RNG_CR); 103c6a97c42SDaniel Thompson 104c6a97c42SDaniel Thompson /* clear error indicators */ 105c6a97c42SDaniel Thompson writel_relaxed(0, priv->base + RNG_SR); 106c6a97c42SDaniel Thompson 107c6a97c42SDaniel Thompson return 0; 108c6a97c42SDaniel Thompson } 109c6a97c42SDaniel Thompson 110c6a97c42SDaniel Thompson static void stm32_rng_cleanup(struct hwrng *rng) 111c6a97c42SDaniel Thompson { 112c6a97c42SDaniel Thompson struct stm32_rng_private *priv = 113c6a97c42SDaniel Thompson container_of(rng, struct stm32_rng_private, rng); 114c6a97c42SDaniel Thompson 115c6a97c42SDaniel Thompson writel_relaxed(0, priv->base + RNG_CR); 116c6a97c42SDaniel Thompson clk_disable_unprepare(priv->clk); 117c6a97c42SDaniel Thompson } 118c6a97c42SDaniel Thompson 119c6a97c42SDaniel Thompson static int stm32_rng_probe(struct platform_device *ofdev) 120c6a97c42SDaniel Thompson { 121c6a97c42SDaniel Thompson struct device *dev = &ofdev->dev; 122c6a97c42SDaniel Thompson struct device_node *np = ofdev->dev.of_node; 123c6a97c42SDaniel Thompson struct stm32_rng_private *priv; 124c6a97c42SDaniel Thompson struct resource res; 125c6a97c42SDaniel Thompson int err; 126c6a97c42SDaniel Thompson 127c6a97c42SDaniel Thompson priv = devm_kzalloc(dev, sizeof(struct stm32_rng_private), GFP_KERNEL); 128c6a97c42SDaniel Thompson if (!priv) 129c6a97c42SDaniel Thompson return -ENOMEM; 130c6a97c42SDaniel Thompson 131c6a97c42SDaniel Thompson err = of_address_to_resource(np, 0, &res); 132c6a97c42SDaniel Thompson if (err) 133c6a97c42SDaniel Thompson return err; 134c6a97c42SDaniel Thompson 135c6a97c42SDaniel Thompson priv->base = devm_ioremap_resource(dev, &res); 136c6a97c42SDaniel Thompson if (IS_ERR(priv->base)) 137c6a97c42SDaniel Thompson return PTR_ERR(priv->base); 138c6a97c42SDaniel Thompson 139c6a97c42SDaniel Thompson priv->clk = devm_clk_get(&ofdev->dev, NULL); 140c6a97c42SDaniel Thompson if (IS_ERR(priv->clk)) 141c6a97c42SDaniel Thompson return PTR_ERR(priv->clk); 142c6a97c42SDaniel Thompson 143c6a97c42SDaniel Thompson dev_set_drvdata(dev, priv); 144c6a97c42SDaniel Thompson 145c6a97c42SDaniel Thompson priv->rng.name = dev_driver_string(dev), 146c6a97c42SDaniel Thompson #ifndef CONFIG_PM 147c6a97c42SDaniel Thompson priv->rng.init = stm32_rng_init, 148c6a97c42SDaniel Thompson priv->rng.cleanup = stm32_rng_cleanup, 149c6a97c42SDaniel Thompson #endif 150c6a97c42SDaniel Thompson priv->rng.read = stm32_rng_read, 151c6a97c42SDaniel Thompson priv->rng.priv = (unsigned long) dev; 152c6a97c42SDaniel Thompson 153c6a97c42SDaniel Thompson pm_runtime_set_autosuspend_delay(dev, 100); 154c6a97c42SDaniel Thompson pm_runtime_use_autosuspend(dev); 155c6a97c42SDaniel Thompson pm_runtime_enable(dev); 156c6a97c42SDaniel Thompson 157c6a97c42SDaniel Thompson return devm_hwrng_register(dev, &priv->rng); 158c6a97c42SDaniel Thompson } 159c6a97c42SDaniel Thompson 160c6a97c42SDaniel Thompson #ifdef CONFIG_PM 161c6a97c42SDaniel Thompson static int stm32_rng_runtime_suspend(struct device *dev) 162c6a97c42SDaniel Thompson { 163d6ba06b8SDaniel Thompson struct stm32_rng_private *priv = dev_get_drvdata(dev); 164c6a97c42SDaniel Thompson 165c6a97c42SDaniel Thompson stm32_rng_cleanup(&priv->rng); 166c6a97c42SDaniel Thompson 167c6a97c42SDaniel Thompson return 0; 168c6a97c42SDaniel Thompson } 169c6a97c42SDaniel Thompson 170c6a97c42SDaniel Thompson static int stm32_rng_runtime_resume(struct device *dev) 171c6a97c42SDaniel Thompson { 172d6ba06b8SDaniel Thompson struct stm32_rng_private *priv = dev_get_drvdata(dev); 173c6a97c42SDaniel Thompson 174c6a97c42SDaniel Thompson return stm32_rng_init(&priv->rng); 175c6a97c42SDaniel Thompson } 176c6a97c42SDaniel Thompson #endif 177c6a97c42SDaniel Thompson 178c6a97c42SDaniel Thompson static UNIVERSAL_DEV_PM_OPS(stm32_rng_pm_ops, stm32_rng_runtime_suspend, 179c6a97c42SDaniel Thompson stm32_rng_runtime_resume, NULL); 180c6a97c42SDaniel Thompson 181c6a97c42SDaniel Thompson static const struct of_device_id stm32_rng_match[] = { 182c6a97c42SDaniel Thompson { 183c6a97c42SDaniel Thompson .compatible = "st,stm32-rng", 184c6a97c42SDaniel Thompson }, 185c6a97c42SDaniel Thompson {}, 186c6a97c42SDaniel Thompson }; 187c6a97c42SDaniel Thompson MODULE_DEVICE_TABLE(of, stm32_rng_match); 188c6a97c42SDaniel Thompson 189c6a97c42SDaniel Thompson static struct platform_driver stm32_rng_driver = { 190c6a97c42SDaniel Thompson .driver = { 191c6a97c42SDaniel Thompson .name = "stm32-rng", 192c6a97c42SDaniel Thompson .pm = &stm32_rng_pm_ops, 193c6a97c42SDaniel Thompson .of_match_table = stm32_rng_match, 194c6a97c42SDaniel Thompson }, 195c6a97c42SDaniel Thompson .probe = stm32_rng_probe, 196c6a97c42SDaniel Thompson }; 197c6a97c42SDaniel Thompson 198c6a97c42SDaniel Thompson module_platform_driver(stm32_rng_driver); 199c6a97c42SDaniel Thompson 200c6a97c42SDaniel Thompson MODULE_LICENSE("GPL"); 201c6a97c42SDaniel Thompson MODULE_AUTHOR("Daniel Thompson <daniel.thompson@linaro.org>"); 202c6a97c42SDaniel Thompson MODULE_DESCRIPTION("STMicroelectronics STM32 RNG device driver"); 203