Date: Tue, 25 Nov 2014 13:54:28 -0700 From: Warner Losh <imp@bsdimp.com> To: =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@des.no> Cc: arch@freebsd.org, Mark R V Murray <mark@grondar.org>, Ian Lepore <ian@FreeBSD.org> Subject: Re: svn commit: r274739 - head/sys/mips/conf Message-ID: <3676CE09-A68A-40F2-8D4A-F821DCD0CF0D@bsdimp.com> In-Reply-To: <86mw7fjf4n.fsf@nine.des.no> References: <201411200552.sAK5qnXP063073@svn.freebsd.org> <20141121092245.GI99957@funkthat.com> <1416582989.1147.250.camel@revolution.hippie.lan> <026FEB8A-CA8C-472F-A8E4-DA3D0AC44B34@grondar.org> <1416596266.1147.290.camel@revolution.hippie.lan> <F017033A-B761-4435-A7F8-264D2F4662A0@grondar.org> <1416598889.1147.297.camel@revolution.hippie.lan> <86egsvueqk.fsf@nine.des.no> <1416691274.1147.339.camel@revolution.hippie.lan> <398A380D-49AF-480C-8842-8835F81EF641@grondar.org> <1416806894.1147.362.camel@revolution.hippie.lan> <18B8A926-59C0-49B4-ADA3-A11688609852@grondar.org> <1416841268.1147.386.camel@revolution.hippie.lan> <CC6B67E1-55A2-4952-AB43-5F6C787F629B@grondar.org> <86wq6k9okk.fsf@nine.des.no> <F60907B5-433F-4800-82B4-5D882AF0B3BB@grondar.org> <8661e3wtk6.fsf@nine.des.no> <D928DF64-2C5D-4D31-A7BE-62482A53A7EA@grondar.org> <86oarvvaet.fsf@nine.des.no> <86egsrxypx.fsf@nine.des.no> <1416925387.1147.437.camel@revolution.hippie.lan> <86mw7fjf4n.fsf@nine.des.no>
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--Apple-Mail=_BF3D74F7-77DD-41E0-807F-9446E0705751 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=utf-8 > On Nov 25, 2014, at 11:42 AM, Dag-Erling Sm=C3=B8rgrav <des@des.no> = wrote: >=20 > Ian Lepore <ian@FreeBSD.org> writes: >> The clock all this is being measured with runs at 32 KHz. That's = 'K'. >=20 > That explains a lot. >=20 > Is there absolutely no instruction counter in this chip? Any other > devices we can use, such as temperature sensors or ADCs? There=E2=80=99s no temperature sensors or useful ADCs. Many of the chips don=E2=80=99t have any ADC. Some have ADCs, but the OS can=E2=80=99t = necessarily use them easily in the boot process. Any ADCs that we might have on the chip (and it varies from chip to chip which we won=E2=80=99t know = until late in the boot process) aren=E2=80=99t necessarily wired to anything and often times share pins with other functions which could be quite disruptive to bring on line (ADC on an unconnected line on these chips likely isn=E2=80=99t going to give that much entropy since = you=E2=80=99re measuring grounded pins). There=E2=80=99s really no good sources of entropy in these systems until unpredictable peripherals get online (network, SD cards, etc) and then it is too late. These chips are based on the ARM920 and ARM926 cores, which don=E2=80=99t have instruction counters, unlike their newer brethren. = This is fairly typical of the embedded space: unless you really need feature X, it is omitted. Warner --Apple-Mail=_BF3D74F7-77DD-41E0-807F-9446E0705751 Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc Content-Description: Message signed with OpenPGP using GPGMail -----BEGIN PGP SIGNATURE----- Comment: GPGTools - https://gpgtools.org iQIcBAEBCgAGBQJUdOyEAAoJEGwc0Sh9sBEA/a4P+QEEXtzd5JAkWu8R6t0f29he IWIDMxsgew8SQXMUyMG9yK/TDv3DW2it9EKbO2xA/zCJRp149N1mWo14ek6O3dDj Pmi0bGKba7pO16j6Gpaj6oCAno4jSOyyYR6jxpRHGlAbcngiFZZOjSy6bXmGK6IM w9cRDp91CqmH4wHnKsDofEEGEjFo8R+79fPcQOlMcUXYzbLcTC1r7AKla6/ZLSd5 hdmOLzdByaoD1BPpdnWJzW/52Tf2U85Y7nR7273IOZ9Q/8KWEj23TOPoiN7rZILr TfX7irME5OjMXQtW5FavpWoJQjywihfzfKFTKeW2KI4zi8+3P4u7LqRbGuKcgnBQ WRc/nZLbW0SzisIcrfUJ6RrP7hwaCctE3pXw8t2xTUIuiQQ0dO+dwdATQ4ofhQT1 d2D7HgxxPjMgdUG19LnechPKPo2Ghuy1mv8iDSHRqYO90qidMZlH4E7giP5aQZzL wZS0yHapUukL+oz1OtCeclHUHN4PE/M7nokC2ukOwgtZ10z9tDRaIou4yLprmDH6 DWKEbqVJUjtvrvpvxcnj1xTvQPVfRcnNjw+fRu2lCQHmgeZjjVroJTub/wV3dbYN kL9j9uS+IIyS41HQKYzxIeY3Cq+YvU8t/cvZV306oWxSxYS1+oh4BT86Kr30p+uP 2uv1EVp+v/lhRuUSH+Qy =l0MD -----END PGP SIGNATURE----- --Apple-Mail=_BF3D74F7-77DD-41E0-807F-9446E0705751--
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