[PATCH 1/2] dev/clock: add bcm2835-system-timer driver

[Ning Yang]

This patch ports the bcm2835 system timer driver in the arm/raspberrypi directory to the shared directory.

Made some changes in the include section to adapt to rpi4 BSP.
---
 bsps/shared/dev/clock/bcm2835-system-timer.c | 114 +++++++++++++++++++
 1 file changed, 114 insertions(+)
 create mode 100644 bsps/shared/dev/clock/bcm2835-system-timer.c

diff --git a/bsps/shared/dev/clock/bcm2835-system-timer.c b/bsps/shared/dev/clock/bcm2835-system-timer.c
new file mode 100644
index 0000000000..f59c9e5424
--- /dev/null
+++ b/bsps/shared/dev/clock/bcm2835-system-timer.c
@@ -0,0 +1,114 @@
+/**
+ * @file
+ *
+ * @ingroup RTEMSDriverClockImpl
+ *
+ * @brief This source file contains the implementation of the BCM2835 Clock
+ *   Driver.
+ */
+
+/*
+ * Copyright (c) 2013 Alan Cudmore
+ * Copyright (c) 2016 Pavel Pisa
+ *
+ *  The license and distribution terms for this file may be
+ *  found in the file LICENSE in this distribution or at
+ *
+ *  http://www.rtems.org/license/LICENSE
+ *
+*/
+
+#include <rtems.h>
+#include <bsp.h>
+#include <bsp/irq.h>
+#include <bsp/irq-generic.h>
+
+#if RTEMS_BSP == raspberrypi4b
+#include <bsp/bcm2711.h>
+#else
+#include <bsp/raspberrypi.h>
+#endif /* RTEMS_BSP */
+
+#include <rtems/timecounter.h>
+
+#define BCM2835_REG(addr)          *(volatile uint32_t*)(addr)
+
+/* This is defined in ../../../shared/dev/clock/clockimpl.h */
+void Clock_isr(rtems_irq_hdl_param arg);
+
+static struct timecounter raspberrypi_tc;
+
+static uint32_t raspberrypi_clock_get_timecount(struct timecounter *tc)
+{
+  return BCM2835_REG(BCM2835_GPU_TIMER_CLO);
+}
+
+static void raspberrypi_clock_at_tick(void)
+{
+  uint32_t act_val;
+  uint32_t next_cmp = BCM2835_REG(BCM2835_GPU_TIMER_C3);
+  next_cmp += rtems_configuration_get_microseconds_per_tick();
+  BCM2835_REG(BCM2835_GPU_TIMER_C3) = next_cmp;
+  act_val = BCM2835_REG(BCM2835_GPU_TIMER_CLO);
+
+  /*
+   * Clear interrupt only if there is time left to the next tick.
+   * If time of the next tick has already passed then interrupt
+   * request stays active and fires immediately after current tick
+   * processing is finished.
+   */
+  if ((int32_t)(next_cmp - act_val) > 0)
+    BCM2835_REG(BCM2835_GPU_TIMER_CS) = BCM2835_GPU_TIMER_CS_M3;
+}
+
+static void raspberrypi_clock_handler_install_isr(
+  rtems_isr_entry clock_isr
+)
+{
+  rtems_status_code sc = RTEMS_SUCCESSFUL;
+
+  if (clock_isr != NULL) {
+    sc = rtems_interrupt_handler_install(
+      BCM2835_IRQ_ID_GPU_TIMER_M3,
+      "Clock",
+      RTEMS_INTERRUPT_UNIQUE,
+      (rtems_interrupt_handler) clock_isr,
+      NULL
+    );
+  } else {
+    /* Remove interrupt handler */
+    sc = rtems_interrupt_handler_remove(
+      BCM2835_IRQ_ID_GPU_TIMER_M3,
+      (rtems_interrupt_handler) Clock_isr,
+      NULL
+    );
+  }
+  if ( sc != RTEMS_SUCCESSFUL ) {
+    rtems_fatal_error_occurred(0xdeadbeef);
+  }
+}
+
+static void raspberrypi_clock_initialize_hardware(void)
+{
+  uint32_t next_cmp = BCM2835_REG(BCM2835_GPU_TIMER_CLO);
+  next_cmp += rtems_configuration_get_microseconds_per_tick();
+  BCM2835_REG(BCM2835_GPU_TIMER_C3) = next_cmp;
+  BCM2835_REG(BCM2835_GPU_TIMER_CS) = BCM2835_GPU_TIMER_CS_M3;
+
+  raspberrypi_tc.tc_get_timecount = raspberrypi_clock_get_timecount;
+  raspberrypi_tc.tc_counter_mask = 0xffffffff;
+  raspberrypi_tc.tc_frequency = 1000000; /* 1 MHz */
+  raspberrypi_tc.tc_quality = RTEMS_TIMECOUNTER_QUALITY_CLOCK_DRIVER;
+  rtems_timecounter_install(&raspberrypi_tc);
+}
+
+#define Clock_driver_support_at_tick() raspberrypi_clock_at_tick()
+
+#define Clock_driver_support_initialize_hardware() raspberrypi_clock_initialize_hardware()
+
+#define Clock_driver_support_install_isr(clock_isr) \
+  raspberrypi_clock_handler_install_isr(clock_isr)
+
+#define CLOCK_DRIVER_USE_ONLY_BOOT_PROCESSOR 1
+
+#include "../../../shared/dev/clock/clockimpl.h"
-- 
2.34.1