static/freebsd/man4/man4.arm/imx6_snvs.4 3.html


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<table class="head">
  <tr>
    <td class="head-ltitle">IMX6_SNVS(4)</td>
    <td class="head-vol">Device Drivers Manual (arm)</td>
    <td class="head-rtitle">IMX6_SNVS(4)</td>
  </tr>
</table>
<div class="manual-text">
<section class="Sh">
<h1 class="Sh" id="NAME"><a class="permalink" href="#NAME">NAME</a></h1>
<p class="Pp"><code class="Nm">imx6_snvs</code> &#x2014; <span class="Nd">device
    driver for the NXP i.MX6 on-chip Realtime Clock</span></p>
</section>
<section class="Sh">
<h1 class="Sh" id="SYNOPSIS"><a class="permalink" href="#SYNOPSIS">SYNOPSIS</a></h1>
<p class="Pp">To compile this driver into the kernel, place the following line
    in your kernel configuration file:</p>
<div class="Bd Pp Bd-indent"><code class="Cd">device imx6_snvs</code></div>
<p class="Pp">Alternatively, to load the driver as a module at boot time, place
    the following line in <a class="Xr">loader.conf(5)</a>:</p>
<div class="Bd Pp Bd-indent Li">
<pre>imx6_snvs_load=&quot;YES&quot;</pre>
</div>
</section>
<section class="Sh">
<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1>
<p class="Pp">The <code class="Nm">imx6_snvs</code> driver provides support for
    the i.MX6 on-chip realtime clock. It provides the time of day with a
    resolution of approximately 30 microseconds.</p>
<p class="Pp">&#x2018;SNVS&#x2019; stands for Secure Non-Volatile Storage, and
    refers to the subsystem within the chip that (optionally) remains powered by
    a battery when the rest of the system is powered down. The on-chip realtime
    clock is part of that subsystem. Other features of the SNVS subsystem are
    related to security, tamper monitoring, and power control; the
    <code class="Nm">imx6_snvs</code> driver does not currently support those
    features.</p>
<p class="Pp">Many i.MX6 systems do not use a battery to provide power to the
    SNVS due to its relatively high power draw. In such systems, this driver is
    able to provide a very accurate time following a reboot, but cannot provide
    time at all if the power is cycled. If the system provides an i2c or other
    type of alternate realtime clock with lower resolution, there is value in
    configuring both clock drivers. Doing so allows SNVS to provide accurate
    time after a reboot, while the external clock provides approximate time
    after power cycling.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="HISTORY"><a class="permalink" href="#HISTORY">HISTORY</a></h1>
<p class="Pp">The <code class="Nm">imx6_snvs</code> driver first appeared in
    <span class="Ux">FreeBSD 12.0</span>.</p>
</section>
</div>
<table class="foot">
  <tr>
    <td class="foot-date">July 8, 2018</td>
    <td class="foot-os">FreeBSD 15.0</td>
  </tr>
</table>