xref: /openbmc/linux/drivers/crypto/caam/caamrng.c (revision e23feb16)
1 /*
2  * caam - Freescale FSL CAAM support for hw_random
3  *
4  * Copyright 2011 Freescale Semiconductor, Inc.
5  *
6  * Based on caamalg.c crypto API driver.
7  *
8  * relationship between job descriptors to shared descriptors:
9  *
10  * ---------------                     --------------
11  * | JobDesc #0  |-------------------->| ShareDesc  |
12  * | *(buffer 0) |      |------------->| (generate) |
13  * ---------------      |              | (move)     |
14  *                      |              | (store)    |
15  * ---------------      |              --------------
16  * | JobDesc #1  |------|
17  * | *(buffer 1) |
18  * ---------------
19  *
20  * A job desc looks like this:
21  *
22  * ---------------------
23  * | Header            |
24  * | ShareDesc Pointer |
25  * | SEQ_OUT_PTR       |
26  * | (output buffer)   |
27  * ---------------------
28  *
29  * The SharedDesc never changes, and each job descriptor points to one of two
30  * buffers for each device, from which the data will be copied into the
31  * requested destination
32  */
33 
34 #include <linux/hw_random.h>
35 #include <linux/completion.h>
36 #include <linux/atomic.h>
37 
38 #include "compat.h"
39 
40 #include "regs.h"
41 #include "intern.h"
42 #include "desc_constr.h"
43 #include "jr.h"
44 #include "error.h"
45 
46 /*
47  * Maximum buffer size: maximum number of random, cache-aligned bytes that
48  * will be generated and moved to seq out ptr (extlen not allowed)
49  */
50 #define RN_BUF_SIZE			(0xffff / L1_CACHE_BYTES * \
51 					 L1_CACHE_BYTES)
52 
53 /* length of descriptors */
54 #define DESC_JOB_O_LEN			(CAAM_CMD_SZ * 2 + CAAM_PTR_SZ * 2)
55 #define DESC_RNG_LEN			(10 * CAAM_CMD_SZ)
56 
57 /* Buffer, its dma address and lock */
58 struct buf_data {
59 	u8 buf[RN_BUF_SIZE];
60 	dma_addr_t addr;
61 	struct completion filled;
62 	u32 hw_desc[DESC_JOB_O_LEN];
63 #define BUF_NOT_EMPTY 0
64 #define BUF_EMPTY 1
65 #define BUF_PENDING 2  /* Empty, but with job pending --don't submit another */
66 	atomic_t empty;
67 };
68 
69 /* rng per-device context */
70 struct caam_rng_ctx {
71 	struct device *jrdev;
72 	dma_addr_t sh_desc_dma;
73 	u32 sh_desc[DESC_RNG_LEN];
74 	unsigned int cur_buf_idx;
75 	int current_buf;
76 	struct buf_data bufs[2];
77 };
78 
79 static struct caam_rng_ctx rng_ctx;
80 
81 static inline void rng_unmap_buf(struct device *jrdev, struct buf_data *bd)
82 {
83 	if (bd->addr)
84 		dma_unmap_single(jrdev, bd->addr, RN_BUF_SIZE,
85 				 DMA_FROM_DEVICE);
86 }
87 
88 static inline void rng_unmap_ctx(struct caam_rng_ctx *ctx)
89 {
90 	struct device *jrdev = ctx->jrdev;
91 
92 	if (ctx->sh_desc_dma)
93 		dma_unmap_single(jrdev, ctx->sh_desc_dma, DESC_RNG_LEN,
94 				 DMA_TO_DEVICE);
95 	rng_unmap_buf(jrdev, &ctx->bufs[0]);
96 	rng_unmap_buf(jrdev, &ctx->bufs[1]);
97 }
98 
99 static void rng_done(struct device *jrdev, u32 *desc, u32 err, void *context)
100 {
101 	struct buf_data *bd;
102 
103 	bd = (struct buf_data *)((char *)desc -
104 	      offsetof(struct buf_data, hw_desc));
105 
106 	if (err) {
107 		char tmp[CAAM_ERROR_STR_MAX];
108 
109 		dev_err(jrdev, "%08x: %s\n", err, caam_jr_strstatus(tmp, err));
110 	}
111 
112 	atomic_set(&bd->empty, BUF_NOT_EMPTY);
113 	complete(&bd->filled);
114 #ifdef DEBUG
115 	print_hex_dump(KERN_ERR, "rng refreshed buf@: ",
116 		       DUMP_PREFIX_ADDRESS, 16, 4, bd->buf, RN_BUF_SIZE, 1);
117 #endif
118 }
119 
120 static inline int submit_job(struct caam_rng_ctx *ctx, int to_current)
121 {
122 	struct buf_data *bd = &ctx->bufs[!(to_current ^ ctx->current_buf)];
123 	struct device *jrdev = ctx->jrdev;
124 	u32 *desc = bd->hw_desc;
125 	int err;
126 
127 	dev_dbg(jrdev, "submitting job %d\n", !(to_current ^ ctx->current_buf));
128 	init_completion(&bd->filled);
129 	err = caam_jr_enqueue(jrdev, desc, rng_done, ctx);
130 	if (err)
131 		complete(&bd->filled); /* don't wait on failed job*/
132 	else
133 		atomic_inc(&bd->empty); /* note if pending */
134 
135 	return err;
136 }
137 
138 static int caam_read(struct hwrng *rng, void *data, size_t max, bool wait)
139 {
140 	struct caam_rng_ctx *ctx = &rng_ctx;
141 	struct buf_data *bd = &ctx->bufs[ctx->current_buf];
142 	int next_buf_idx, copied_idx;
143 	int err;
144 
145 	if (atomic_read(&bd->empty)) {
146 		/* try to submit job if there wasn't one */
147 		if (atomic_read(&bd->empty) == BUF_EMPTY) {
148 			err = submit_job(ctx, 1);
149 			/* if can't submit job, can't even wait */
150 			if (err)
151 				return 0;
152 		}
153 		/* no immediate data, so exit if not waiting */
154 		if (!wait)
155 			return 0;
156 
157 		/* waiting for pending job */
158 		if (atomic_read(&bd->empty))
159 			wait_for_completion(&bd->filled);
160 	}
161 
162 	next_buf_idx = ctx->cur_buf_idx + max;
163 	dev_dbg(ctx->jrdev, "%s: start reading at buffer %d, idx %d\n",
164 		 __func__, ctx->current_buf, ctx->cur_buf_idx);
165 
166 	/* if enough data in current buffer */
167 	if (next_buf_idx < RN_BUF_SIZE) {
168 		memcpy(data, bd->buf + ctx->cur_buf_idx, max);
169 		ctx->cur_buf_idx = next_buf_idx;
170 		return max;
171 	}
172 
173 	/* else, copy what's left... */
174 	copied_idx = RN_BUF_SIZE - ctx->cur_buf_idx;
175 	memcpy(data, bd->buf + ctx->cur_buf_idx, copied_idx);
176 	ctx->cur_buf_idx = 0;
177 	atomic_set(&bd->empty, BUF_EMPTY);
178 
179 	/* ...refill... */
180 	submit_job(ctx, 1);
181 
182 	/* and use next buffer */
183 	ctx->current_buf = !ctx->current_buf;
184 	dev_dbg(ctx->jrdev, "switched to buffer %d\n", ctx->current_buf);
185 
186 	/* since there already is some data read, don't wait */
187 	return copied_idx + caam_read(rng, data + copied_idx,
188 				      max - copied_idx, false);
189 }
190 
191 static inline void rng_create_sh_desc(struct caam_rng_ctx *ctx)
192 {
193 	struct device *jrdev = ctx->jrdev;
194 	u32 *desc = ctx->sh_desc;
195 
196 	init_sh_desc(desc, HDR_SHARE_SERIAL);
197 
198 	/* Propagate errors from shared to job descriptor */
199 	append_cmd(desc, SET_OK_NO_PROP_ERRORS | CMD_LOAD);
200 
201 	/* Generate random bytes */
202 	append_operation(desc, OP_ALG_ALGSEL_RNG | OP_TYPE_CLASS1_ALG);
203 
204 	/* Store bytes */
205 	append_seq_fifo_store(desc, RN_BUF_SIZE, FIFOST_TYPE_RNGSTORE);
206 
207 	ctx->sh_desc_dma = dma_map_single(jrdev, desc, desc_bytes(desc),
208 					  DMA_TO_DEVICE);
209 #ifdef DEBUG
210 	print_hex_dump(KERN_ERR, "rng shdesc@: ", DUMP_PREFIX_ADDRESS, 16, 4,
211 		       desc, desc_bytes(desc), 1);
212 #endif
213 }
214 
215 static inline void rng_create_job_desc(struct caam_rng_ctx *ctx, int buf_id)
216 {
217 	struct device *jrdev = ctx->jrdev;
218 	struct buf_data *bd = &ctx->bufs[buf_id];
219 	u32 *desc = bd->hw_desc;
220 	int sh_len = desc_len(ctx->sh_desc);
221 
222 	init_job_desc_shared(desc, ctx->sh_desc_dma, sh_len, HDR_SHARE_DEFER |
223 			     HDR_REVERSE);
224 
225 	bd->addr = dma_map_single(jrdev, bd->buf, RN_BUF_SIZE, DMA_FROM_DEVICE);
226 
227 	append_seq_out_ptr_intlen(desc, bd->addr, RN_BUF_SIZE, 0);
228 #ifdef DEBUG
229 	print_hex_dump(KERN_ERR, "rng job desc@: ", DUMP_PREFIX_ADDRESS, 16, 4,
230 		       desc, desc_bytes(desc), 1);
231 #endif
232 }
233 
234 static void caam_cleanup(struct hwrng *rng)
235 {
236 	int i;
237 	struct buf_data *bd;
238 
239 	for (i = 0; i < 2; i++) {
240 		bd = &rng_ctx.bufs[i];
241 		if (atomic_read(&bd->empty) == BUF_PENDING)
242 			wait_for_completion(&bd->filled);
243 	}
244 
245 	rng_unmap_ctx(&rng_ctx);
246 }
247 
248 static void caam_init_buf(struct caam_rng_ctx *ctx, int buf_id)
249 {
250 	struct buf_data *bd = &ctx->bufs[buf_id];
251 
252 	rng_create_job_desc(ctx, buf_id);
253 	atomic_set(&bd->empty, BUF_EMPTY);
254 	submit_job(ctx, buf_id == ctx->current_buf);
255 	wait_for_completion(&bd->filled);
256 }
257 
258 static void caam_init_rng(struct caam_rng_ctx *ctx, struct device *jrdev)
259 {
260 	ctx->jrdev = jrdev;
261 	rng_create_sh_desc(ctx);
262 	ctx->current_buf = 0;
263 	ctx->cur_buf_idx = 0;
264 	caam_init_buf(ctx, 0);
265 	caam_init_buf(ctx, 1);
266 }
267 
268 static struct hwrng caam_rng = {
269 	.name		= "rng-caam",
270 	.cleanup	= caam_cleanup,
271 	.read		= caam_read,
272 };
273 
274 static void __exit caam_rng_exit(void)
275 {
276 	hwrng_unregister(&caam_rng);
277 }
278 
279 static int __init caam_rng_init(void)
280 {
281 	struct device_node *dev_node;
282 	struct platform_device *pdev;
283 	struct device *ctrldev;
284 	struct caam_drv_private *priv;
285 
286 	dev_node = of_find_compatible_node(NULL, NULL, "fsl,sec-v4.0");
287 	if (!dev_node) {
288 		dev_node = of_find_compatible_node(NULL, NULL, "fsl,sec4.0");
289 		if (!dev_node)
290 			return -ENODEV;
291 	}
292 
293 	pdev = of_find_device_by_node(dev_node);
294 	if (!pdev)
295 		return -ENODEV;
296 
297 	ctrldev = &pdev->dev;
298 	priv = dev_get_drvdata(ctrldev);
299 	of_node_put(dev_node);
300 
301 	caam_init_rng(&rng_ctx, priv->jrdev[0]);
302 
303 	dev_info(priv->jrdev[0], "registering rng-caam\n");
304 	return hwrng_register(&caam_rng);
305 }
306 
307 module_init(caam_rng_init);
308 module_exit(caam_rng_exit);
309 
310 MODULE_LICENSE("GPL");
311 MODULE_DESCRIPTION("FSL CAAM support for hw_random API");
312 MODULE_AUTHOR("Freescale Semiconductor - NMG");
313