staging: comedi: addi_apci_3120: introduce apci3120_ns_to_timer()

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The timer divisor calculations in this driver are over complicated.

There are three timers on the board. They all use the same base clock
with a fixed prescaler for each timer. The base clock used depends on
the board version and type:

  APCI-3120 Rev A boards OSC = 14.29MHz base clock (~70ns)
  APCI-3120 Rev B boards OSC = 20MHz base clock (50ns)
  APCI-3001 boards OSC = 20MHz base clock (50ns)

The prescalers for each timer are:

  Timer 0 CLK = OSC/10
  Timer 1 CLK = OSC/1000
  Timer 2 CLK = OSC/1000

Add a new member to the private data, 'osc_base', to hold the base clock
time. Set this member during the board attach.

Introduce a helper function to calculate the divisor needed to generate
a nanosecond time with a given timer.

Use the new helper function in the driver to clarify the code.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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H Hartley Sweeten 2014-11-04 10:53:45 -07:00 • committed by Greg Kroah-Hartman

parent 48d43be475

commit 546bf3382e

2 changed files with 100 additions and 108 deletions

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137

drivers/staging/comedi/drivers/addi-data/hwdrv_apci3120.c

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71

drivers/staging/comedi/drivers/addi_apci_3120.c

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