Upstream bug: kernel pps-gpio driver only reports one edge.

Module authors notified.

1 files changed, 10 insertions, 0 deletions

diff --git a/www/upstream-bugs.html b/www/upstream-bugs.html
index 2f041d69..55fc01c1 100644
--- a/www/upstream-bugs.html
+++ b/www/upstream-bugs.html
@@ -66,6 +66,7 @@ maintainer, we've tried to kick these upstream.</p>
 <ul>
 <li><a href="#osx-pl2303">Unknown osx-pl2303 driver issues on Mac OS X</a></li> 
 <li><a href="#tiocmwait">PPS fails: ioctl(TIOCMIWAIT) hangs after tcsetattr()</a></li>
+<li><a href="#pps-gpio">The pps-gpio driver only reports on one edge</a></li>
 <li><a href="#bluetooth">Firmware problems in some Bluetooth and USB devices can hang them</a></li>
 <li><a href="#pl2303">Linux pl2303 driver on openwrt 2.4 kernel can hang when device is read at unexpected speed</a></li>
 <li><a href="#pthread_create">pthread_create() fails to return when called in background</a></li>
@@ -126,6 +127,15 @@ the same device from ever resuming. This interferes with PPS support</p>
 <p>The workaround is to use stty to pre-set the serial port to the right
 baud rate so tcsetattr is never called.</p>
 
+<h2 id="pps-gpio">The pps-gpio only reports on one edge</h2>
+
+<p>The pps-gpio driver only looks at the clear edge to determine the
+time of the PPS pulse.  Many GPS use the other edge, so the reported
+time may be offset by the PPS pulse width.</p>
+
+<p>Problem is present in Linux 3.19 and earlier.  The module authors
+have been notified</p>
+
 <h2 id="bluetooth">Firmware problems in some Bluetooth and USB devices can hang them</h2>
 
 <p>The baudrate-hunting code in <code>gpsd</code> tickles a serious