1d2912cb1SThomas Gleixner // SPDX-License-Identifier: GPL-2.0-only 24a4da53cSLee Jones /* 34a4da53cSLee Jones * ST Random Number Generator Driver ST's Platforms 44a4da53cSLee Jones * 54a4da53cSLee Jones * Author: Pankaj Dev: <pankaj.dev@st.com> 64a4da53cSLee Jones * Lee Jones <lee.jones@linaro.org> 74a4da53cSLee Jones * 84a4da53cSLee Jones * Copyright (C) 2015 STMicroelectronics (R&D) Limited 94a4da53cSLee Jones */ 104a4da53cSLee Jones 114a4da53cSLee Jones #include <linux/clk.h> 124a4da53cSLee Jones #include <linux/delay.h> 134a4da53cSLee Jones #include <linux/hw_random.h> 144a4da53cSLee Jones #include <linux/io.h> 154a4da53cSLee Jones #include <linux/module.h> 164a4da53cSLee Jones #include <linux/of.h> 174a4da53cSLee Jones #include <linux/platform_device.h> 184a4da53cSLee Jones #include <linux/slab.h> 194a4da53cSLee Jones 204a4da53cSLee Jones /* Registers */ 214a4da53cSLee Jones #define ST_RNG_STATUS_REG 0x20 224a4da53cSLee Jones #define ST_RNG_DATA_REG 0x24 234a4da53cSLee Jones 244a4da53cSLee Jones /* Registers fields */ 254a4da53cSLee Jones #define ST_RNG_STATUS_BAD_SEQUENCE BIT(0) 264a4da53cSLee Jones #define ST_RNG_STATUS_BAD_ALTERNANCE BIT(1) 274a4da53cSLee Jones #define ST_RNG_STATUS_FIFO_FULL BIT(5) 284a4da53cSLee Jones 294a4da53cSLee Jones #define ST_RNG_SAMPLE_SIZE 2 /* 2 Byte (16bit) samples */ 309ad92bdfSLee Jones #define ST_RNG_FIFO_DEPTH 4 319ad92bdfSLee Jones #define ST_RNG_FIFO_SIZE (ST_RNG_FIFO_DEPTH * ST_RNG_SAMPLE_SIZE) 324a4da53cSLee Jones 3393d649bdSLee Jones /* 3493d649bdSLee Jones * Samples are documented to be available every 0.667us, so in theory 3593d649bdSLee Jones * the 4 sample deep FIFO should take 2.668us to fill. However, during 3693d649bdSLee Jones * thorough testing, it became apparent that filling the FIFO actually 3793d649bdSLee Jones * takes closer to 12us. We then multiply by 2 in order to account for 3893d649bdSLee Jones * the lack of udelay()'s reliability, suggested by Russell King. 3993d649bdSLee Jones */ 4093d649bdSLee Jones #define ST_RNG_FILL_FIFO_TIMEOUT (12 * 2) 414a4da53cSLee Jones 424a4da53cSLee Jones struct st_rng_data { 434a4da53cSLee Jones void __iomem *base; 444a4da53cSLee Jones struct clk *clk; 454a4da53cSLee Jones struct hwrng ops; 464a4da53cSLee Jones }; 474a4da53cSLee Jones 484a4da53cSLee Jones static int st_rng_read(struct hwrng *rng, void *data, size_t max, bool wait) 494a4da53cSLee Jones { 504a4da53cSLee Jones struct st_rng_data *ddata = (struct st_rng_data *)rng->priv; 514a4da53cSLee Jones u32 status; 524a4da53cSLee Jones int i; 534a4da53cSLee Jones 544a4da53cSLee Jones /* Wait until FIFO is full - max 4uS*/ 554a4da53cSLee Jones for (i = 0; i < ST_RNG_FILL_FIFO_TIMEOUT; i++) { 564a4da53cSLee Jones status = readl_relaxed(ddata->base + ST_RNG_STATUS_REG); 574a4da53cSLee Jones if (status & ST_RNG_STATUS_FIFO_FULL) 584a4da53cSLee Jones break; 594a4da53cSLee Jones udelay(1); 604a4da53cSLee Jones } 614a4da53cSLee Jones 624a4da53cSLee Jones if (i == ST_RNG_FILL_FIFO_TIMEOUT) 634a4da53cSLee Jones return 0; 644a4da53cSLee Jones 654a4da53cSLee Jones for (i = 0; i < ST_RNG_FIFO_SIZE && i < max; i += 2) 664a4da53cSLee Jones *(u16 *)(data + i) = 674a4da53cSLee Jones readl_relaxed(ddata->base + ST_RNG_DATA_REG); 684a4da53cSLee Jones 694a4da53cSLee Jones return i; /* No of bytes read */ 704a4da53cSLee Jones } 714a4da53cSLee Jones 724a4da53cSLee Jones static int st_rng_probe(struct platform_device *pdev) 734a4da53cSLee Jones { 744a4da53cSLee Jones struct st_rng_data *ddata; 754a4da53cSLee Jones struct resource *res; 764a4da53cSLee Jones struct clk *clk; 774a4da53cSLee Jones void __iomem *base; 784a4da53cSLee Jones int ret; 794a4da53cSLee Jones 804a4da53cSLee Jones ddata = devm_kzalloc(&pdev->dev, sizeof(*ddata), GFP_KERNEL); 814a4da53cSLee Jones if (!ddata) 824a4da53cSLee Jones return -ENOMEM; 834a4da53cSLee Jones 844a4da53cSLee Jones res = platform_get_resource(pdev, IORESOURCE_MEM, 0); 854a4da53cSLee Jones base = devm_ioremap_resource(&pdev->dev, res); 864a4da53cSLee Jones if (IS_ERR(base)) 874a4da53cSLee Jones return PTR_ERR(base); 884a4da53cSLee Jones 894a4da53cSLee Jones clk = devm_clk_get(&pdev->dev, NULL); 904a4da53cSLee Jones if (IS_ERR(clk)) 914a4da53cSLee Jones return PTR_ERR(clk); 924a4da53cSLee Jones 934a4da53cSLee Jones ret = clk_prepare_enable(clk); 944a4da53cSLee Jones if (ret) 954a4da53cSLee Jones return ret; 964a4da53cSLee Jones 974a4da53cSLee Jones ddata->ops.priv = (unsigned long)ddata; 984a4da53cSLee Jones ddata->ops.read = st_rng_read; 994a4da53cSLee Jones ddata->ops.name = pdev->name; 1004a4da53cSLee Jones ddata->base = base; 1014a4da53cSLee Jones ddata->clk = clk; 1024a4da53cSLee Jones 1034a4da53cSLee Jones dev_set_drvdata(&pdev->dev, ddata); 1044a4da53cSLee Jones 1053e75241bSChuhong Yuan ret = devm_hwrng_register(&pdev->dev, &ddata->ops); 1064a4da53cSLee Jones if (ret) { 1074a4da53cSLee Jones dev_err(&pdev->dev, "Failed to register HW RNG\n"); 10894879fa8SWei Yongjun clk_disable_unprepare(clk); 1094a4da53cSLee Jones return ret; 1104a4da53cSLee Jones } 1114a4da53cSLee Jones 1124a4da53cSLee Jones dev_info(&pdev->dev, "Successfully registered HW RNG\n"); 1134a4da53cSLee Jones 1144a4da53cSLee Jones return 0; 1154a4da53cSLee Jones } 1164a4da53cSLee Jones 1174a4da53cSLee Jones static int st_rng_remove(struct platform_device *pdev) 1184a4da53cSLee Jones { 1194a4da53cSLee Jones struct st_rng_data *ddata = dev_get_drvdata(&pdev->dev); 1204a4da53cSLee Jones 1214a4da53cSLee Jones clk_disable_unprepare(ddata->clk); 1224a4da53cSLee Jones 1234a4da53cSLee Jones return 0; 1244a4da53cSLee Jones } 1254a4da53cSLee Jones 1264a4da53cSLee Jones static const struct of_device_id st_rng_match[] = { 1274a4da53cSLee Jones { .compatible = "st,rng" }, 1284a4da53cSLee Jones {}, 1294a4da53cSLee Jones }; 1304a4da53cSLee Jones MODULE_DEVICE_TABLE(of, st_rng_match); 1314a4da53cSLee Jones 1324a4da53cSLee Jones static struct platform_driver st_rng_driver = { 1334a4da53cSLee Jones .driver = { 1344a4da53cSLee Jones .name = "st-hwrandom", 1354a4da53cSLee Jones .of_match_table = of_match_ptr(st_rng_match), 1364a4da53cSLee Jones }, 1374a4da53cSLee Jones .probe = st_rng_probe, 1384a4da53cSLee Jones .remove = st_rng_remove 1394a4da53cSLee Jones }; 1404a4da53cSLee Jones 1414a4da53cSLee Jones module_platform_driver(st_rng_driver); 1424a4da53cSLee Jones 1434a4da53cSLee Jones MODULE_AUTHOR("Pankaj Dev <pankaj.dev@st.com>"); 1444a4da53cSLee Jones MODULE_LICENSE("GPL v2"); 145