Re: [PATCH v2 2/3] ARM: DRA7x: dts: Update the OSC_32K_CLK frequency

From	Matthijs van Duin <matthijsvanduin@gmail.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2 2/3] ARM: DRA7x: dts: Update the OSC_32K_CLK frequency
Date	2016-05-04 16:20 +0200
Message-ID	<rv5OG-5wR-27@gated-at.bofh.it> (permalink)
References	(2 earlier) <ruDIL-4pf-29@gated-at.bofh.it> <ruDIL-4pf-27@gated-at.bofh.it> <ruLGi-33K-11@gated-at.bofh.it> <ruLGi-33K-9@gated-at.bofh.it> <ruMsG-3Sd-11@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On 3 May 2016 at 18:43, Tony Lindgren <tony@atomide.com> wrote:
> Does a fixed divider calculation of input * (32768 / 27e6) make sense
> here too as pointed out earlier by Matthijs for the ti81xx?

That was an actual fractional divider, i.e. the output clock would be
exactly that ratio of the input clock, which would therefore yield
32768 Hz if the default crystal is used for the main osc.

It makes no sense to use it to describe a wobbly RC osc.

On 3 May 2016 at 19:32, Tero Kristo <t-kristo@ti.com> wrote:
> Also, as it is security related, this is kind of sensitive area to discuss publicly.

Don't be silly. The only sense in which this clock is "security
related" is because it's used for the secure watchdog, and the reason
to use it despite its inaccuracy is completely obvious: an internal rc
osc can't be easily manipulated by an external attacker. I see no
reason to act all cloak-and-dagger about this.

(This seems to be a general theme to conceal "security related" things
from public documentation. If I were an HS customer I'd actually be
concerned about such behaviour since it would seem to indicate a lack
of confidence in one's security architecture.)

Matthijs

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

Re: [PATCH v2 2/3] ARM: DRA7x: dts: Update the OSC_32K_CLK frequency Tero Kristo <t-kristo@ti.com> - 2016-05-03 10:20 +0200
  Re: [PATCH v2 2/3] ARM: DRA7x: dts: Update the OSC_32K_CLK frequency Tony Lindgren <tony@atomide.com> - 2016-05-03 18:50 +0200
    Re: [PATCH v2 2/3] ARM: DRA7x: dts: Update the OSC_32K_CLK frequency Tero Kristo <t-kristo@ti.com> - 2016-05-03 19:40 +0200
      Re: [PATCH v2 2/3] ARM: DRA7x: dts: Update the OSC_32K_CLK frequency Tony Lindgren <tony@atomide.com> - 2016-05-03 20:10 +0200
      Re: [PATCH v2 2/3] ARM: DRA7x: dts: Update the OSC_32K_CLK frequency Tero Kristo <t-kristo@ti.com> - 2016-05-03 20:20 +0200
        Re: [PATCH v2 2/3] ARM: DRA7x: dts: Update the OSC_32K_CLK frequency Nishanth Menon <nm@ti.com> - 2016-05-04 01:20 +0200
      Re: [PATCH v2 2/3] ARM: DRA7x: dts: Update the OSC_32K_CLK frequency Matthijs van Duin <matthijsvanduin@gmail.com> - 2016-05-04 16:20 +0200

csiph-web