[PATCH 0/1] Adds QEP driver to Beaglebone BSP

[James Fitzsimons]

This patch adds driver support for the eQEP (enhanced Quadrature Encoder Pulse) 
module within each of the PWMSS units in the AM335x. The eQEP module is used for 
hardware decoding of rotrary encoders, motor encoders etc. 

Because the PWMSS module includes several components some of the existing code in
the pwm driver could be reused. To make this common I have added a pwmss.h header
and moved some of the pwmss specific defines and enum to this file. The pwmss.c
file contains a refactored (simplified) version of the clock configuration
method that was previously in the pwm.c file. The pwmss_module_clk_config will
now be shared by both the pwm and eqep drivers (and eventually the ecap driver if
that is ever added).

The approach taken with the qep.h header was to move some of the qep specific 
defines from the am335x.h header to this file. They are specific to the qep 
function and would likely never be referenced by anything other than this driver.
Doing this keeps these definitions with the driver code and reduces clutter in 
am335x.h header.

The driver supports two primary modes of operation. A polled mode (which is the
default mode), and an interrupt event driven mode.

The one area of the patch that I am least happy with and could do with some advice on 
is the callback approach I have used for the interrupt event driven model. Here a 
unit timer is configured with a set time period (in nanoseconds) and on expiry the unit
timer raises an interrupt. The interrupt handler calls an optional callback function that
the user can supply when setting the unit timer period via the beagle_eqep_set_timer_period. Although this works ok, I realise that calling a user 
function from a OS level interrupt is not desirable. Better suggestions for this would be
gratefully received.

I will send a follow up email including some sample test programs with their associated 
output.

Regards,
James

James Fitzsimons (1):
  Adding QEP driver to Beaglebone bsp

 bsps/arm/beagle/headers.am              |   2 +
 bsps/arm/beagle/include/bsp/bbb-pwm.h   |  11 -
 bsps/arm/beagle/include/bsp/pwmss.h     |  54 +++
 bsps/arm/beagle/include/bsp/qep.h       | 331 ++++++++++++++++++
 bsps/arm/beagle/pwm/pwm.c               |  64 +---
 bsps/arm/beagle/pwmss/pwmss.c           |  64 ++++
 bsps/arm/beagle/qep/qep.c               | 435 ++++++++++++++++++++++++
 c/src/lib/libbsp/arm/beagle/Makefile.am |   6 +
 8 files changed, 896 insertions(+), 71 deletions(-)
 create mode 100644 bsps/arm/beagle/include/bsp/pwmss.h
 create mode 100644 bsps/arm/beagle/include/bsp/qep.h
 create mode 100644 bsps/arm/beagle/pwmss/pwmss.c
 create mode 100644 bsps/arm/beagle/qep/qep.c

-- 
2.17.1