Alternative clock driver. Uses exception handler

directly.  Supports special variants for Book E and e300 cores.  For
standard decrementer CPUs the new decrementer value is calculated with
reference to a time base so that a time drift is avoided

1 files changed, 271 insertions, 0 deletions

diff --git a/c/src/lib/libbsp/powerpc/shared/clock/clock.c b/c/src/lib/libbsp/powerpc/shared/clock/clock.c
new file mode 100644
index 0000000000..85f7db60b7
--- /dev/null
+++ b/c/src/lib/libbsp/powerpc/shared/clock/clock.c
@@ -0,0 +1,271 @@
+/**
+ * @file
+ *
+ * @ingroup powerpc_shared
+ *
+ * @brief Source file for a clock driver.
+ */
+
+/*
+ * Copyright (c) 2008
+ * Embedded Brains GmbH
+ * Obere Lagerstr. 30
+ * D-82178 Puchheim
+ * Germany
+ * rtems@embedded-brains.de
+ *
+ * The license and distribution terms for this file may be found in the file
+ * LICENSE in this distribution or at http://www.rtems.com/license/LICENSE.
+ */
+
+#include <rtems/libio.h>
+#include <rtems/clockdrv.h>
+
+#include <libcpu/powerpc-utility.h>
+#include <libcpu/raw_exception.h>
+
+#include <bsp/ppc_exc_bspsupp.h>
+
+#define RTEMS_STATUS_CHECKS_USE_PRINTK
+
+#include <rtems/status-checks.h>
+
+/*
+ * This variable must be defined in the BSP and valid before clock driver
+ * initialization.  The clicks refer to the decrementer and time base.
+ */
+extern uint32_t bsp_clicks_per_usec;
+
+#define PPC_CLOCK_DECREMENTER_MAX UINT32_MAX
+
+volatile uint32_t Clock_driver_ticks = 0;
+
+rtems_device_major_number rtems_clock_major = -1;
+
+rtems_device_minor_number rtems_clock_minor = -1;
+
+static uint32_t ppc_clock_decrementer_value = PPC_CLOCK_DECREMENTER_MAX;
+
+static uint32_t ppc_clock_next_time_base = 0;
+
+static void ppc_clock_no_tick()
+{
+	/* Do nothing */
+}
+
+static void (*ppc_clock_tick)() = ppc_clock_no_tick;
+
+int ppc_clock_exception_handler( BSP_Exception_frame *frame, unsigned number)
+{
+	uint32_t reg1;
+	uint32_t reg2;
+	uint32_t reg3;
+	uint32_t msr;
+
+	/* Set new decrementer value according to a reference time base */
+	asm volatile (
+		"lwz %0, ppc_clock_next_time_base@sdarel(13);"
+		"lwz %1, ppc_clock_decrementer_value@sdarel(13);"
+		"mftb %2;"
+		"add %0, %0, %1;"
+		"subf %1, %2, %0;"
+		"stw %0, ppc_clock_next_time_base@sdarel(13);"
+		"mtdec %1;"
+		: "=r" (reg1), "=r" (reg2), "=r" (reg3)
+	);
+
+	/* Increment clock ticks */
+	Clock_driver_ticks += 1;
+
+	/* Enable external exceptions */
+	msr = ppc_external_exceptions_enable();
+
+	/* Call clock ticker  */
+	ppc_clock_tick();
+
+	/* Restore machine state */
+	ppc_external_exceptions_disable( msr);
+
+	return 0;
+}
+
+int ppc_clock_exception_handler_classic( BSP_Exception_frame *frame, unsigned number)
+{
+	uint32_t reg1;
+	uint32_t reg2;
+	uint32_t msr;
+
+	/* Set new decrementer value */
+	asm volatile(
+		"lwz %1, ppc_clock_decrementer_value@sdarel(13);"
+		"mfdec %0;"
+		"add %0, %0, %1;"
+		"mtdec %0"
+		: "=r" (reg1), "=r" (reg2)
+	);
+
+	/* Increment clock ticks */
+	Clock_driver_ticks += 1;
+
+	/* Enable external exceptions */
+	msr = ppc_external_exceptions_enable();
+
+	/* Call clock ticker  */
+	ppc_clock_tick();
+
+	/* Restore machine state */
+	ppc_external_exceptions_disable( msr);
+
+	return 0;
+}
+
+int ppc_clock_exception_handler_booke( BSP_Exception_frame *frame, unsigned number)
+{
+	uint32_t msr;
+
+	/* Acknowledge decrementer request */
+	ppc_set_timer_status_register( BOOKE_TSR_DIS);
+
+	/* Increment clock ticks */
+	Clock_driver_ticks += 1;
+
+	/* Enable external exceptions */
+	msr = ppc_external_exceptions_enable();
+
+	/* Call clock ticker  */
+	ppc_clock_tick();
+
+	/* Restore machine state */
+	ppc_external_exceptions_disable( msr);
+
+	return 0;
+}
+
+int ppc_clock_exception_handler_e300( BSP_Exception_frame *frame, unsigned number)
+{
+	uint32_t msr;
+
+	/* Increment clock ticks */
+	Clock_driver_ticks += 1;
+
+	/* Enable external exceptions */
+	msr = ppc_external_exceptions_enable();
+
+	/* Call clock ticker  */
+	ppc_clock_tick();
+
+	/* Restore machine state */
+	ppc_external_exceptions_disable( msr);
+
+	return 0;
+}
+
+uint32_t ppc_clock_nanoseconds_since_last_tick()
+{
+	return ((ppc_clock_decrementer_value - ppc_decrementer_register()) * 1000) / bsp_clicks_per_usec;
+}
+
+void Clock_exit()
+{
+	/* Set the decrementer to the maximum value */
+	ppc_set_decrementer_register( PPC_CLOCK_DECREMENTER_MAX);
+
+	/* Use default clock handler */
+	ppc_clock_tick = ppc_clock_no_tick;
+}
+
+rtems_device_driver Clock_initialize( rtems_device_major_number major, rtems_device_minor_number minor, void *arg)
+{
+	rtems_interrupt_level level;
+
+	/* Current CPU type */
+	ppc_cpu_id_t cpu_type = get_ppc_cpu_type();
+
+	/* Make major/minor available to others such as shared memory driver */
+	rtems_clock_major = major;
+	rtems_clock_minor = minor;
+
+	/*
+	 * Set default ticker.
+	 * 
+	 * The function rtems_clock_tick() returns a status code.  This value
+	 * will be discarded since the RTEMS documentation claims that it is
+	 * always successful.
+	 */
+	ppc_clock_tick = (void (*)()) rtems_clock_tick;
+
+	/* Set the decrementer to the maximum value */
+	ppc_set_decrementer_register( PPC_CLOCK_DECREMENTER_MAX);
+
+	/* Decrementer value */
+	ppc_clock_decrementer_value = bsp_clicks_per_usec * rtems_configuration_get_microseconds_per_tick() - 1;
+
+	/* Check decrementer value */
+	if (ppc_clock_decrementer_value == 0) {
+		ppc_clock_decrementer_value = PPC_CLOCK_DECREMENTER_MAX;
+		SYSLOG_ERROR( "Decrementer value would be zero, will be set to maximum value instead\n");
+	}
+
+	/* Set the nanoseconds since last tick handler */
+	rtems_clock_set_nanoseconds_extension( ppc_clock_nanoseconds_since_last_tick);
+
+	if (ppc_cpu_is_bookE()) {
+		/* Set decrementer auto-reload value */
+		ppc_set_decrementer_auto_reload_register( ppc_clock_decrementer_value);
+
+		/* Install exception handler */
+		ppc_exc_set_handler( ASM_BOOKE_DEC_VECTOR, ppc_clock_exception_handler_booke);
+
+		/* Enable decrementer and auto-reload */
+		rtems_interrupt_disable( level);
+		ppc_set_timer_control_register( ppc_timer_control_register() | BOOKE_TCR_DIE | BOOKE_TCR_ARE);
+		rtems_interrupt_enable( level);
+	} else if (cpu_type == PPC_e300c2 || cpu_type == PPC_e300c3) {
+		/* TODO: Not tested for e300c2 */
+
+		/* Enable auto-reload */
+		rtems_interrupt_disable( level);
+		ppc_set_hardware_implementation_dependent_register_0( ppc_hardware_implementation_dependent_register_0() | 0x00000040);
+		rtems_interrupt_enable( level);
+
+		/* Install exception handler */
+		ppc_exc_set_handler( ASM_DEC_VECTOR, ppc_clock_exception_handler_e300);
+	} else {
+		/* Here the decrementer value is actually the interval */
+		++ppc_clock_decrementer_value;
+
+		rtems_interrupt_disable( level);
+
+		/* Initialize next time base */
+		ppc_clock_next_time_base = ppc_time_base() + ppc_clock_decrementer_value;
+
+		/* Install exception handler */
+		ppc_exc_set_handler( ASM_DEC_VECTOR, ppc_clock_exception_handler);
+
+		rtems_interrupt_enable( level);
+	}
+
+	/* Set the decrementer value */
+	ppc_set_decrementer_register( ppc_clock_decrementer_value);
+
+	return RTEMS_SUCCESSFUL;
+}
+
+rtems_device_driver Clock_control( rtems_device_major_number major, rtems_device_minor_number minor, void *arg)
+{
+	rtems_libio_ioctl_args_t *io = arg;
+
+	if (io == NULL) {
+		return RTEMS_SUCCESSFUL;
+	} else if (ppc_clock_tick == NULL) {
+		Clock_initialize( major, minor, 0);
+	}
+
+	if (io->command == rtems_build_name( 'I', 'S', 'R', ' ')) {
+		ppc_clock_tick();
+	} else if (io->command == rtems_build_name( 'N', 'E', 'W', ' ')) {
+		ppc_clock_tick = io->buffer;
+	}
+
+	return RTEMS_SUCCESSFUL;
+}