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The probe function enables the TRNG hardware before registering the driver. If registration fails, probe returns an error, but the TRNG remains enabled. Define init and cleanup functions, enable and disable the hardware there. Signed-off-by: Martin Kaiser <martin@kaiser.cx> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
122 lines
2.9 KiB
C
122 lines
2.9 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* PIC32 RNG driver
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*
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* Joshua Henderson <joshua.henderson@microchip.com>
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* Copyright (C) 2016 Microchip Technology Inc. All rights reserved.
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*/
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#include <linux/clk.h>
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#include <linux/clkdev.h>
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#include <linux/err.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/of_device.h>
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#include <linux/platform_device.h>
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#include <linux/slab.h>
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#define RNGCON 0x04
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#define TRNGEN BIT(8)
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#define TRNGMOD BIT(11)
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#define RNGSEED1 0x18
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#define RNGSEED2 0x1C
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#define RNGRCNT 0x20
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#define RCNT_MASK 0x7F
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struct pic32_rng {
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void __iomem *base;
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struct hwrng rng;
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};
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/*
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* The TRNG can generate up to 24Mbps. This is a timeout that should be safe
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* enough given the instructions in the loop and that the TRNG may not always
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* be at maximum rate.
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*/
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#define RNG_TIMEOUT 500
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static int pic32_rng_init(struct hwrng *rng)
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{
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struct pic32_rng *priv = container_of(rng, struct pic32_rng, rng);
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/* enable TRNG in enhanced mode */
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writel(TRNGEN | TRNGMOD, priv->base + RNGCON);
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return 0;
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}
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static int pic32_rng_read(struct hwrng *rng, void *buf, size_t max,
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bool wait)
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{
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struct pic32_rng *priv = container_of(rng, struct pic32_rng, rng);
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u64 *data = buf;
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u32 t;
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unsigned int timeout = RNG_TIMEOUT;
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do {
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t = readl(priv->base + RNGRCNT) & RCNT_MASK;
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if (t == 64) {
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/* TRNG value comes through the seed registers */
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*data = ((u64)readl(priv->base + RNGSEED2) << 32) +
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readl(priv->base + RNGSEED1);
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return 8;
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}
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} while (wait && --timeout);
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return -EIO;
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}
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static void pic32_rng_cleanup(struct hwrng *rng)
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{
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struct pic32_rng *priv = container_of(rng, struct pic32_rng, rng);
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writel(0, priv->base + RNGCON);
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}
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static int pic32_rng_probe(struct platform_device *pdev)
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{
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struct pic32_rng *priv;
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struct clk *clk;
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priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
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if (!priv)
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return -ENOMEM;
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priv->base = devm_platform_ioremap_resource(pdev, 0);
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if (IS_ERR(priv->base))
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return PTR_ERR(priv->base);
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clk = devm_clk_get_enabled(&pdev->dev, NULL);
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if (IS_ERR(clk))
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return PTR_ERR(clk);
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priv->rng.name = pdev->name;
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priv->rng.init = pic32_rng_init;
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priv->rng.read = pic32_rng_read;
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priv->rng.cleanup = pic32_rng_cleanup;
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return devm_hwrng_register(&pdev->dev, &priv->rng);
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}
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static const struct of_device_id pic32_rng_of_match[] __maybe_unused = {
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{ .compatible = "microchip,pic32mzda-rng", },
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{ /* sentinel */ }
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};
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MODULE_DEVICE_TABLE(of, pic32_rng_of_match);
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static struct platform_driver pic32_rng_driver = {
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.probe = pic32_rng_probe,
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.driver = {
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.name = "pic32-rng",
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.of_match_table = of_match_ptr(pic32_rng_of_match),
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},
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};
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module_platform_driver(pic32_rng_driver);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Joshua Henderson <joshua.henderson@microchip.com>");
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MODULE_DESCRIPTION("Microchip PIC32 RNG Driver");
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