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>
15ad237562SHerbert Xu #include <linux/kernel.h>
164a4da53cSLee Jones #include <linux/module.h>
174a4da53cSLee Jones #include <linux/of.h>
184a4da53cSLee Jones #include <linux/platform_device.h>
194a4da53cSLee Jones #include <linux/slab.h>
204a4da53cSLee Jones
214a4da53cSLee Jones /* Registers */
224a4da53cSLee Jones #define ST_RNG_STATUS_REG 0x20
234a4da53cSLee Jones #define ST_RNG_DATA_REG 0x24
244a4da53cSLee Jones
254a4da53cSLee Jones /* Registers fields */
264a4da53cSLee Jones #define ST_RNG_STATUS_BAD_SEQUENCE BIT(0)
274a4da53cSLee Jones #define ST_RNG_STATUS_BAD_ALTERNANCE BIT(1)
284a4da53cSLee Jones #define ST_RNG_STATUS_FIFO_FULL BIT(5)
294a4da53cSLee Jones
304a4da53cSLee Jones #define ST_RNG_SAMPLE_SIZE 2 /* 2 Byte (16bit) samples */
319ad92bdfSLee Jones #define ST_RNG_FIFO_DEPTH 4
329ad92bdfSLee Jones #define ST_RNG_FIFO_SIZE (ST_RNG_FIFO_DEPTH * ST_RNG_SAMPLE_SIZE)
334a4da53cSLee Jones
3493d649bdSLee Jones /*
3593d649bdSLee Jones * Samples are documented to be available every 0.667us, so in theory
3693d649bdSLee Jones * the 4 sample deep FIFO should take 2.668us to fill. However, during
3793d649bdSLee Jones * thorough testing, it became apparent that filling the FIFO actually
3893d649bdSLee Jones * takes closer to 12us. We then multiply by 2 in order to account for
3993d649bdSLee Jones * the lack of udelay()'s reliability, suggested by Russell King.
4093d649bdSLee Jones */
4193d649bdSLee Jones #define ST_RNG_FILL_FIFO_TIMEOUT (12 * 2)
424a4da53cSLee Jones
434a4da53cSLee Jones struct st_rng_data {
444a4da53cSLee Jones void __iomem *base;
454a4da53cSLee Jones struct hwrng ops;
464a4da53cSLee Jones };
474a4da53cSLee Jones
st_rng_read(struct hwrng * rng,void * data,size_t max,bool wait)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
st_rng_probe(struct platform_device * pdev)724a4da53cSLee Jones static int st_rng_probe(struct platform_device *pdev)
734a4da53cSLee Jones {
744a4da53cSLee Jones struct st_rng_data *ddata;
754a4da53cSLee Jones struct clk *clk;
764a4da53cSLee Jones void __iomem *base;
774a4da53cSLee Jones int ret;
784a4da53cSLee Jones
794a4da53cSLee Jones ddata = devm_kzalloc(&pdev->dev, sizeof(*ddata), GFP_KERNEL);
804a4da53cSLee Jones if (!ddata)
814a4da53cSLee Jones return -ENOMEM;
824a4da53cSLee Jones
83bd74b0f5SYueHaibing base = devm_platform_ioremap_resource(pdev, 0);
844a4da53cSLee Jones if (IS_ERR(base))
854a4da53cSLee Jones return PTR_ERR(base);
864a4da53cSLee Jones
87*501e197aSMartin Kaiser clk = devm_clk_get_enabled(&pdev->dev, NULL);
884a4da53cSLee Jones if (IS_ERR(clk))
894a4da53cSLee Jones return PTR_ERR(clk);
904a4da53cSLee Jones
914a4da53cSLee Jones ddata->ops.priv = (unsigned long)ddata;
924a4da53cSLee Jones ddata->ops.read = st_rng_read;
934a4da53cSLee Jones ddata->ops.name = pdev->name;
944a4da53cSLee Jones ddata->base = base;
954a4da53cSLee Jones
963e75241bSChuhong Yuan ret = devm_hwrng_register(&pdev->dev, &ddata->ops);
974a4da53cSLee Jones if (ret) {
984a4da53cSLee Jones dev_err(&pdev->dev, "Failed to register HW RNG\n");
994a4da53cSLee Jones return ret;
1004a4da53cSLee Jones }
1014a4da53cSLee Jones
1024a4da53cSLee Jones dev_info(&pdev->dev, "Successfully registered HW RNG\n");
1034a4da53cSLee Jones
1044a4da53cSLee Jones return 0;
1054a4da53cSLee Jones }
1064a4da53cSLee Jones
107ad237562SHerbert Xu static const struct of_device_id st_rng_match[] __maybe_unused = {
1084a4da53cSLee Jones { .compatible = "st,rng" },
1094a4da53cSLee Jones {},
1104a4da53cSLee Jones };
1114a4da53cSLee Jones MODULE_DEVICE_TABLE(of, st_rng_match);
1124a4da53cSLee Jones
1134a4da53cSLee Jones static struct platform_driver st_rng_driver = {
1144a4da53cSLee Jones .driver = {
1154a4da53cSLee Jones .name = "st-hwrandom",
1164a4da53cSLee Jones .of_match_table = of_match_ptr(st_rng_match),
1174a4da53cSLee Jones },
1184a4da53cSLee Jones .probe = st_rng_probe,
1194a4da53cSLee Jones };
1204a4da53cSLee Jones
1214a4da53cSLee Jones module_platform_driver(st_rng_driver);
1224a4da53cSLee Jones
1234a4da53cSLee Jones MODULE_AUTHOR("Pankaj Dev <pankaj.dev@st.com>");
1244a4da53cSLee Jones MODULE_LICENSE("GPL v2");
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