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amdccp.c revision 1.1 
      1 /* $NetBSD: amdccp.c,v 1.1 2018/10/19 21:09:10 jakllsch Exp $ */
      2 
      3 /*
      4  * Copyright (c) 2018 Jonathan A. Kollasch
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     17  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
     20  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
     21  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     22  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
     23  * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
     24  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
     25  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
     26  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 #include <sys/cdefs.h>
     30 
     31 __KERNEL_RCSID(0, "$NetBSD: amdccp.c,v 1.1 2018/10/19 21:09:10 jakllsch Exp $");
     32 
     33 #include <sys/param.h>
     34 #include <sys/systm.h>
     35 #include <sys/device.h>
     36 #include <sys/bus.h>
     37 #include <sys/rndpool.h>
     38 #include <sys/rndsource.h>
     39 
     40 #include <dev/ic/amdccpvar.h>
     41 
     42 static uint32_t amdccp_rnd_read(struct amdccp_softc *);
     43 static void amdccp_rnd_callback(size_t, void *);
     44 
     45 void
     46 amdccp_common_attach(struct amdccp_softc *sc)
     47 {
     48 	mutex_init(&sc->sc_rndlock, MUTEX_DEFAULT, IPL_VM);
     49 	rndsource_setcb(&sc->sc_rndsource, amdccp_rnd_callback, sc);
     50 	rnd_attach_source(&sc->sc_rndsource, device_xname(sc->sc_dev),
     51 	    RND_TYPE_RNG, RND_FLAG_COLLECT_VALUE|RND_FLAG_HASCB);
     52 	amdccp_rnd_callback(RND_POOLBITS / NBBY, sc);
     53 }
     54 
     55 static uint32_t
     56 amdccp_rnd_read(struct amdccp_softc *sc)
     57 {
     58 	size_t retries = 5;
     59 	uint32_t bits;
     60 
     61 	/* TRNG register reads 0x0 when bits aren't valid */
     62 	while (retries--) {
     63 		bits = bus_space_read_4(sc->sc_bst, sc->sc_bsh, CCP_TRNG_REG);
     64 		if (bits != 0x0)
     65 			break;
     66 	}
     67 
     68 	return bits;
     69 }
     70 
     71 static void
     72 amdccp_rnd_callback(size_t bytes_wanted, void *priv)
     73 {
     74 	struct amdccp_softc * const sc = priv;
     75 	uint32_t buf[128];
     76 	size_t cnt;
     77 
     78 	mutex_enter(&sc->sc_rndlock);
     79 	while (bytes_wanted) {
     80 		const size_t nbytes = MIN(bytes_wanted, sizeof(buf));
     81 		const size_t nwords = howmany(nbytes, sizeof(buf[0]));
     82 		for (cnt = 0; cnt < nwords; cnt++) {
     83 			buf[cnt] = amdccp_rnd_read(sc);
     84 			if (buf[cnt] == 0) {
     85 				break;
     86 			}
     87 		}
     88 		const size_t cntby = cnt * sizeof(buf[0]);
     89 		rnd_add_data_sync(&sc->sc_rndsource, buf, cntby, cntby * NBBY);
     90 		bytes_wanted -= MIN(bytes_wanted, cntby);
     91 	}
     92 	explicit_memset(buf, 0, sizeof(buf));
     93 	mutex_exit(&sc->sc_rndlock);
     94 }
     95