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// SPDX-License-Identifier: GPL-2.0+
/*
* PRNG driver for Qualcomm IPQ40xx
*
* Copyright (c) 2020 Sartura Ltd.
*
* Author: Robert Marko <robert.marko@sartura.hr>
*
* Based on Linux driver
*/
#include <clk.h>
#include <dm.h>
#include <rng.h>
#include <asm/io.h>
#include <linux/bitops.h>
/* Device specific register offsets */
#define PRNG_DATA_OUT 0x0000
#define PRNG_STATUS 0x0004
#define PRNG_LFSR_CFG 0x0100
#define PRNG_CONFIG 0x0104
/* Device specific register masks and config values */
#define PRNG_LFSR_CFG_MASK 0x0000ffff
#define PRNG_LFSR_CFG_CLOCKS 0x0000dddd
#define PRNG_CONFIG_HW_ENABLE BIT(1)
#define PRNG_STATUS_DATA_AVAIL BIT(0)
#define MAX_HW_FIFO_DEPTH 16
#define MAX_HW_FIFO_SIZE (MAX_HW_FIFO_DEPTH * 4)
#define WORD_SZ 4
struct msm_rng_priv {
phys_addr_t base;
struct clk clk;
};
static int msm_rng_read(struct udevice *dev, void *data, size_t len)
{
struct msm_rng_priv *priv = dev_get_priv(dev);
size_t currsize = 0;
u32 *retdata = data;
size_t maxsize;
u32 val;
/* calculate max size bytes to transfer back to caller */
maxsize = min_t(size_t, MAX_HW_FIFO_SIZE, len);
/* read random data from hardware */
do {
val = readl_relaxed(priv->base + PRNG_STATUS);
if (!(val & PRNG_STATUS_DATA_AVAIL))
break;
val = readl_relaxed(priv->base + PRNG_DATA_OUT);
if (!val)
break;
*retdata++ = val;
currsize += WORD_SZ;
/* make sure we stay on 32bit boundary */
if ((maxsize - currsize) < WORD_SZ)
break;
} while (currsize < maxsize);
return 0;
}
static int msm_rng_enable(struct msm_rng_priv *priv, int enable)
{
u32 val;
if (enable) {
/* Enable PRNG only if it is not already enabled */
val = readl_relaxed(priv->base + PRNG_CONFIG);
if (val & PRNG_CONFIG_HW_ENABLE) {
val = readl_relaxed(priv->base + PRNG_LFSR_CFG);
val &= ~PRNG_LFSR_CFG_MASK;
val |= PRNG_LFSR_CFG_CLOCKS;
writel(val, priv->base + PRNG_LFSR_CFG);
val = readl_relaxed(priv->base + PRNG_CONFIG);
val |= PRNG_CONFIG_HW_ENABLE;
writel(val, priv->base + PRNG_CONFIG);
}
} else {
val = readl_relaxed(priv->base + PRNG_CONFIG);
val &= ~PRNG_CONFIG_HW_ENABLE;
writel(val, priv->base + PRNG_CONFIG);
}
return 0;
}
static int msm_rng_probe(struct udevice *dev)
{
struct msm_rng_priv *priv = dev_get_priv(dev);
int ret;
priv->base = dev_read_addr(dev);
if (priv->base == FDT_ADDR_T_NONE)
return -EINVAL;
ret = clk_get_by_index(dev, 0, &priv->clk);
if (ret)
return ret;
ret = clk_enable(&priv->clk);
if (ret < 0)
return ret;
return msm_rng_enable(priv, 1);
}
static int msm_rng_remove(struct udevice *dev)
{
struct msm_rng_priv *priv = dev_get_priv(dev);
return msm_rng_enable(priv, 0);
}
static const struct dm_rng_ops msm_rng_ops = {
.read = msm_rng_read,
};
static const struct udevice_id msm_rng_match[] = {
{ .compatible = "qcom,prng", },
{},
};
U_BOOT_DRIVER(msm_rng) = {
.name = "msm-rng",
.id = UCLASS_RNG,
.of_match = msm_rng_match,
.ops = &msm_rng_ops,
.probe = msm_rng_probe,
.remove = msm_rng_remove,
.priv_auto = sizeof(struct msm_rng_priv),
};
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