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143 lines
3.4 KiB
143 lines
3.4 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* ST Random Number Generator Driver ST's Platforms |
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* |
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* Author: Pankaj Dev: <[email protected]> |
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* Lee Jones <[email protected]> |
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* |
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* Copyright (C) 2015 STMicroelectronics (R&D) Limited |
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*/ |
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#include <linux/clk.h> |
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#include <linux/delay.h> |
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#include <linux/hw_random.h> |
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#include <linux/io.h> |
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#include <linux/kernel.h> |
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#include <linux/module.h> |
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#include <linux/of.h> |
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#include <linux/platform_device.h> |
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#include <linux/slab.h> |
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/* Registers */ |
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#define ST_RNG_STATUS_REG 0x20 |
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#define ST_RNG_DATA_REG 0x24 |
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/* Registers fields */ |
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#define ST_RNG_STATUS_BAD_SEQUENCE BIT(0) |
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#define ST_RNG_STATUS_BAD_ALTERNANCE BIT(1) |
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#define ST_RNG_STATUS_FIFO_FULL BIT(5) |
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#define ST_RNG_SAMPLE_SIZE 2 /* 2 Byte (16bit) samples */ |
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#define ST_RNG_FIFO_DEPTH 4 |
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#define ST_RNG_FIFO_SIZE (ST_RNG_FIFO_DEPTH * ST_RNG_SAMPLE_SIZE) |
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/* |
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* Samples are documented to be available every 0.667us, so in theory |
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* the 4 sample deep FIFO should take 2.668us to fill. However, during |
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* thorough testing, it became apparent that filling the FIFO actually |
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* takes closer to 12us. We then multiply by 2 in order to account for |
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* the lack of udelay()'s reliability, suggested by Russell King. |
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*/ |
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#define ST_RNG_FILL_FIFO_TIMEOUT (12 * 2) |
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struct st_rng_data { |
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void __iomem *base; |
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struct clk *clk; |
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struct hwrng ops; |
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}; |
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static int st_rng_read(struct hwrng *rng, void *data, size_t max, bool wait) |
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{ |
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struct st_rng_data *ddata = (struct st_rng_data *)rng->priv; |
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u32 status; |
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int i; |
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/* Wait until FIFO is full - max 4uS*/ |
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for (i = 0; i < ST_RNG_FILL_FIFO_TIMEOUT; i++) { |
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status = readl_relaxed(ddata->base + ST_RNG_STATUS_REG); |
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if (status & ST_RNG_STATUS_FIFO_FULL) |
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break; |
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udelay(1); |
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} |
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if (i == ST_RNG_FILL_FIFO_TIMEOUT) |
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return 0; |
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for (i = 0; i < ST_RNG_FIFO_SIZE && i < max; i += 2) |
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*(u16 *)(data + i) = |
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readl_relaxed(ddata->base + ST_RNG_DATA_REG); |
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return i; /* No of bytes read */ |
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} |
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static int st_rng_probe(struct platform_device *pdev) |
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{ |
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struct st_rng_data *ddata; |
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struct clk *clk; |
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void __iomem *base; |
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int ret; |
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ddata = devm_kzalloc(&pdev->dev, sizeof(*ddata), GFP_KERNEL); |
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if (!ddata) |
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return -ENOMEM; |
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base = devm_platform_ioremap_resource(pdev, 0); |
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if (IS_ERR(base)) |
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return PTR_ERR(base); |
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clk = devm_clk_get(&pdev->dev, NULL); |
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if (IS_ERR(clk)) |
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return PTR_ERR(clk); |
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ret = clk_prepare_enable(clk); |
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if (ret) |
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return ret; |
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ddata->ops.priv = (unsigned long)ddata; |
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ddata->ops.read = st_rng_read; |
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ddata->ops.name = pdev->name; |
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ddata->base = base; |
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ddata->clk = clk; |
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dev_set_drvdata(&pdev->dev, ddata); |
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ret = devm_hwrng_register(&pdev->dev, &ddata->ops); |
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if (ret) { |
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dev_err(&pdev->dev, "Failed to register HW RNG\n"); |
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clk_disable_unprepare(clk); |
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return ret; |
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} |
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dev_info(&pdev->dev, "Successfully registered HW RNG\n"); |
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return 0; |
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} |
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static int st_rng_remove(struct platform_device *pdev) |
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{ |
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struct st_rng_data *ddata = dev_get_drvdata(&pdev->dev); |
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clk_disable_unprepare(ddata->clk); |
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return 0; |
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} |
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static const struct of_device_id st_rng_match[] __maybe_unused = { |
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{ .compatible = "st,rng" }, |
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{}, |
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}; |
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MODULE_DEVICE_TABLE(of, st_rng_match); |
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static struct platform_driver st_rng_driver = { |
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.driver = { |
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.name = "st-hwrandom", |
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.of_match_table = of_match_ptr(st_rng_match), |
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}, |
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.probe = st_rng_probe, |
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.remove = st_rng_remove |
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}; |
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module_platform_driver(st_rng_driver); |
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MODULE_AUTHOR("Pankaj Dev <[email protected]>"); |
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MODULE_LICENSE("GPL v2");
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