linux/drivers/crypto/caam/caamrng.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * caam - Freescale FSL CAAM support for hw_random
 *
 * Copyright 2011 Freescale Semiconductor, Inc.
 * Copyright 2018-2019, 2023 NXP
 *
 * Based on caamalg.c crypto API driver.
 *
 */

#include <linux/hw_random.h>
#include <linux/completion.h>
#include <linux/atomic.h>
#include <linux/dma-mapping.h>
#include <linux/kernel.h>
#include <linux/kfifo.h>

#include "compat.h"

#include "regs.h"
#include "intern.h"
#include "desc_constr.h"
#include "jr.h"
#include "error.h"

#define CAAM_RNG_MAX_FIFO_STORE_SIZE	16

/*
 * Length of used descriptors, see caam_init_desc()
 */
#define CAAM_RNG_DESC_LEN (CAAM_CMD_SZ +				\
			   CAAM_CMD_SZ +				\
			   CAAM_CMD_SZ + CAAM_PTR_SZ_MAX)

/* rng per-device context */
struct caam_rng_ctx {
	struct hwrng rng;
	struct device *jrdev;
	struct device *ctrldev;
	void *desc_async;
	void *desc_sync;
	struct work_struct worker;
	struct kfifo fifo;
};

struct caam_rng_job_ctx {
	struct completion *done;
	int *err;
};

static struct caam_rng_ctx *to_caam_rng_ctx(struct hwrng *r)
{
	return (struct caam_rng_ctx *)r->priv;
}

static void caam_rng_done(struct device *jrdev, u32 *desc, u32 err,
			  void *context)
{
	struct caam_rng_job_ctx *jctx = context;

	if (err)
		*jctx->err = caam_jr_strstatus(jrdev, err);

	complete(jctx->done);
}

static u32 *caam_init_desc(u32 *desc, dma_addr_t dst_dma)
{
	init_job_desc(desc, 0);	/* + 1 cmd_sz */
	/* Generate random bytes: + 1 cmd_sz */
	append_operation(desc, OP_ALG_ALGSEL_RNG | OP_TYPE_CLASS1_ALG |
			 OP_ALG_PR_ON);
	/* Store bytes: + 1 cmd_sz + caam_ptr_sz  */
	append_fifo_store(desc, dst_dma,
			  CAAM_RNG_MAX_FIFO_STORE_SIZE, FIFOST_TYPE_RNGSTORE);

	print_hex_dump_debug("rng job desc@: ", DUMP_PREFIX_ADDRESS,
			     16, 4, desc, desc_bytes(desc), 1);

	return desc;
}

static int caam_rng_read_one(struct device *jrdev,
			     void *dst, int len,
			     void *desc,
			     struct completion *done)
{
	dma_addr_t dst_dma;
	int err, ret = 0;
	struct caam_rng_job_ctx jctx = {
		.done = done,
		.err  = &ret,
	};

	len = CAAM_RNG_MAX_FIFO_STORE_SIZE;

	dst_dma = dma_map_single(jrdev, dst, len, DMA_FROM_DEVICE);
	if (dma_mapping_error(jrdev, dst_dma)) {
		dev_err(jrdev, "unable to map destination memory\n");
		return -ENOMEM;
	}

	init_completion(done);
	err = caam_jr_enqueue(jrdev,
			      caam_init_desc(desc, dst_dma),
			      caam_rng_done, &jctx);
	if (err == -EINPROGRESS) {
		wait_for_completion(done);
		err = 0;
	}

	dma_unmap_single(jrdev, dst_dma, len, DMA_FROM_DEVICE);

	return err ?: (ret ?: len);
}

static void caam_rng_fill_async(struct caam_rng_ctx *ctx)
{
	struct scatterlist sg[1];
	struct completion done;
	int len, nents;

	sg_init_table(sg, ARRAY_SIZE(sg));
	nents = kfifo_dma_in_prepare(&ctx->fifo, sg, ARRAY_SIZE(sg),
				     CAAM_RNG_MAX_FIFO_STORE_SIZE);
	if (!nents)
		return;

	len = caam_rng_read_one(ctx->jrdev, sg_virt(&sg[0]),
				sg[0].length,
				ctx->desc_async,
				&done);
	if (len < 0)
		return;

	kfifo_dma_in_finish(&ctx->fifo, len);
}

static void caam_rng_worker(struct work_struct *work)
{
	struct caam_rng_ctx *ctx = container_of(work, struct caam_rng_ctx,
						worker);
	caam_rng_fill_async(ctx);
}

static int caam_read(struct hwrng *rng, void *dst, size_t max, bool wait)
{
	struct caam_rng_ctx *ctx = to_caam_rng_ctx(rng);
	int out;

	if (wait) {
		struct completion done;

		return caam_rng_read_one(ctx->jrdev, dst, max,
					 ctx->desc_sync, &done);
	}

	out = kfifo_out(&ctx->fifo, dst, max);
	if (kfifo_is_empty(&ctx->fifo))
		schedule_work(&ctx->worker);

	return out;
}

static void caam_cleanup(struct hwrng *rng)
{
	struct caam_rng_ctx *ctx = to_caam_rng_ctx(rng);

	flush_work(&ctx->worker);
	caam_jr_free(ctx->jrdev);
	kfifo_free(&ctx->fifo);
}

static int caam_init(struct hwrng *rng)
{
	struct caam_rng_ctx *ctx = to_caam_rng_ctx(rng);
	int err;

	ctx->desc_sync = devm_kzalloc(ctx->ctrldev, CAAM_RNG_DESC_LEN,
				      GFP_KERNEL);
	if (!ctx->desc_sync)
		return -ENOMEM;

	ctx->desc_async = devm_kzalloc(ctx->ctrldev, CAAM_RNG_DESC_LEN,
				       GFP_KERNEL);
	if (!ctx->desc_async)
		return -ENOMEM;

	if (kfifo_alloc(&ctx->fifo, ALIGN(CAAM_RNG_MAX_FIFO_STORE_SIZE,
					  dma_get_cache_alignment()),
			GFP_KERNEL))
		return -ENOMEM;

	INIT_WORK(&ctx->worker, caam_rng_worker);

	ctx->jrdev = caam_jr_alloc();
	err = PTR_ERR_OR_ZERO(ctx->jrdev);
	if (err) {
		kfifo_free(&ctx->fifo);
		pr_err("Job Ring Device allocation for transform failed\n");
		return err;
	}

	/*
	 * Fill async buffer to have early randomness data for
	 * hw_random
	 */
	caam_rng_fill_async(ctx);

	return 0;
}

int caam_rng_init(struct device *ctrldev);

void caam_rng_exit(struct device *ctrldev)
{
	devres_release_group(ctrldev, caam_rng_init);
}

int caam_rng_init(struct device *ctrldev)
{
	struct caam_rng_ctx *ctx;
	u32 rng_inst;
	struct caam_drv_private *priv = dev_get_drvdata(ctrldev);
	int ret;

	/* Check for an instantiated RNG before registration */
	if (priv->era < 10)
		rng_inst = (rd_reg32(&priv->jr[0]->perfmon.cha_num_ls) &
			    CHA_ID_LS_RNG_MASK) >> CHA_ID_LS_RNG_SHIFT;
	else
		rng_inst = rd_reg32(&priv->jr[0]->vreg.rng) & CHA_VER_NUM_MASK;

	if (!rng_inst)
		return 0;

	if (!devres_open_group(ctrldev, caam_rng_init, GFP_KERNEL))
		return -ENOMEM;

	ctx = devm_kzalloc(ctrldev, sizeof(*ctx), GFP_KERNEL);
	if (!ctx)
		return -ENOMEM;

	ctx->ctrldev = ctrldev;

	ctx->rng.name    = "rng-caam";
	ctx->rng.init    = caam_init;
	ctx->rng.cleanup = caam_cleanup;
	ctx->rng.read    = caam_read;
	ctx->rng.priv    = (unsigned long)ctx;

	dev_info(ctrldev, "registering rng-caam\n");

	ret = devm_hwrng_register(ctrldev, &ctx->rng);
	if (ret) {
		caam_rng_exit(ctrldev);
		return ret;
	}

	devres_close_group(ctrldev, caam_rng_init);
	return 0;
}