The attached patch is updated against main line because
of the removal of the jtag_speed command.

jtag_speed removal thread:
https://lists.berlios.de/pipermail/openocd-development/2009-November/012115.html

First try for merge of this path:
http://lists.berlios.de/pipermail/openocd-development/2009-September/010369.html

The attached patch add the khz and speed_div functions to
the parport interface driver.

This enables the jtag_khz command for parport interfaces.

The patch also adds a command named parport_toggling_time
that tells the parport driver how long (in nanoseconds) it
takes for the hardware to toggle the parallel port pins.
The khz and speed_div functions needs this data. The
default setting is 1000 ns.

The default setting should actually be set to the lowest
known toggling time of common hardware. This to guarantee
that the JTAG frequency never is higher than the commanded.
However I can not find data about this and just selected
1000 ns. It can be changed later when someone with knowledge
of this give input.

I do not expect that many parport interface users will
measure their parallel port toggling time. The default
setting will be used. This result in that the full
capacity of the interface is not used when a speed below
500 kHz is commanded.
  I do not think that this is a major issue. In nearly
all cases are speeds below this only used in the initial
setup. After the clock/PLL is setup, the JTAG clock is
switched to a frequency of several MHz.
  The lower than requested speed will thus only affects
the initial board setup. The full capacity of the hardware
will be used for later debugging/flashing.

Best regards
Jonas Hörberg

Attachment: openocd-parport-add-jtag_khz_support.patch
Description: Binary data

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