beagle/pwmss/pwmss.c

0001 /**
0002  * @file
0003  *
0004  * @ingroup arm_beagle
0005  *
0006  * @brief Support for eQEP for the BeagleBone Black.
0007  */
0008
0009 /*
0010  * SPDX-License-Identifier: BSD-2-Clause
0011  *
0012  * Copyright (c) 2020, 2021 James Fitzsimons <james.fitzsimons@gmail.com>
0013  *
0014  * Redistribution and use in source and binary forms, with or without
0015  * modification, are permitted provided that the following conditions
0016  * are met:
0017  * 1. Redistributions of source code must retain the above copyright
0018  *    notice, this list of conditions and the following disclaimer.
0019  * 2. Redistributions in binary form must reproduce the above copyright
0020  *    notice, this list of conditions and the following disclaimer in the
0021  *    documentation and/or other materials provided with the distribution.
0022  *
0023  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
0024  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
0025  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
0026  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
0027  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
0028  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
0029  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
0030  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
0031  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
0032  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
0033  * POSSIBILITY OF SUCH DAMAGE.
0034  */
0035
0036 #include <libcpu/am335x.h>
0037 #include <stdio.h>
0038 #include <bsp.h>
0039 #include <bsp/pwmss.h>
0040 #include <bsp/beagleboneblack.h>
0041 #include <rtems/error.h>
0042
0043 /**
0044  * @brief   This function configures the L3 and L4_PER system clocks.
0045  *          It also configures the system clocks for the specified ePWMSS
0046  *          instance.
0047  *
0048  * @param   pwmss_id    The instance number of ePWMSS whose system clocks
0049  *                         have to be configured.
0050  *
0051  * 'pwmss_id' can take one of the following values:
0052  * (0 <= pwmss_id <= 2)
0053  *
0054  * @return  True if successful
0055  *          False if Unsuccessful
0056  */
0057 rtems_status_code pwmss_module_clk_config(BBB_PWMSS pwmss_id)
0058 {
0059     /* we initialize clkctrl here to nonsentical value as this is going
0060      * to be assigned later anyway. Here assigning 0 is just to kill
0061      * warning emitted by the C compiler. */
0062     uint32_t clkctrl = 0;
0063
0064     /* calculate the address of the clock control register for the PWMSS
0065      * module we are configuring */
0066     if(pwmss_id == BBB_PWMSS0) {
0067         clkctrl = AM335X_CM_PER_ADDR + AM335X_CM_PER_EPWMSS0_CLKCTRL;
0068     } else if(pwmss_id == BBB_PWMSS1) {
0069         clkctrl = AM335X_CM_PER_ADDR + AM335X_CM_PER_EPWMSS1_CLKCTRL;
0070     } else if(pwmss_id == BBB_PWMSS2) {
0071         clkctrl = AM335X_CM_PER_ADDR + AM335X_CM_PER_EPWMSS2_CLKCTRL;
0072     } else {
0073     /* wrong clock configuration, let's panic here. */
0074     rtems_error(RTEMS_ERROR_PANIC, "beagle: unsupported pwmss module clock configuration value!");
0075     }
0076
0077     /* when the module is functional the IDLEST bits (16 -17) of the
0078      * CM_PER_EPWMSSx_CLKCTRL register will be 0x0. */
0079     const uint32_t is_functional = 0x0;
0080     const uint32_t idle_bits = AM335X_CM_PER_EPWMSSx_CLKCTRL_IDLEST;
0081     const uint32_t is_enable = AM335X_CM_PER_EPWMSSx_CLKCTRL_MODULEMODE_ENABLE;
0082     const uint32_t module_mode = AM335X_CM_PER_EPWMSSx_CLKCTRL_MODULEMODE;
0083
0084     REG(clkctrl) |= is_enable;
0085     while((REG(clkctrl) & module_mode) != is_enable);
0086     while((REG(clkctrl) & idle_bits) != is_functional);
0087
0088     return RTEMS_SUCCESSFUL;
0089 }