ARM: Improve documentation in arm_timer.h

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/arch/arm/include/asm/hardware/arm_timer.h b/arch/arm/include/asm/hardware/arm_timer.h
index 04be3bd..c0f4e7b 100644 (file)
--- a/arch/arm/include/asm/hardware/arm_timer.h
+++ b/arch/arm/include/asm/hardware/arm_timer.h
@@ -1,21 +1,30 @@
 #ifndef __ASM_ARM_HARDWARE_ARM_TIMER_H
 #define __ASM_ARM_HARDWARE_ARM_TIMER_H
 
-#define TIMER_LOAD     0x00
-#define TIMER_VALUE    0x04
-#define TIMER_CTRL     0x08
-#define TIMER_CTRL_ONESHOT     (1 << 0)
-#define TIMER_CTRL_32BIT       (1 << 1)
-#define TIMER_CTRL_DIV1                (0 << 2)
-#define TIMER_CTRL_DIV16       (1 << 2)
-#define TIMER_CTRL_DIV256      (2 << 2)
-#define TIMER_CTRL_IE          (1 << 5)        /* Interrupt Enable (versatile only) */
-#define TIMER_CTRL_PERIODIC    (1 << 6)
-#define TIMER_CTRL_ENABLE      (1 << 7)
+/*
+ * ARM timer implementation, found in Integrator, Versatile and Realview
+ * platforms.  Not all platforms support all registers and bits in these
+ * registers, so we mark them with A for Integrator AP, C for Integrator
+ * CP, V for Versatile and R for Realview.
+ *
+ * Integrator AP has 16-bit timers, Integrator CP, Versatile and Realview
+ * can have 16-bit or 32-bit selectable via a bit in the control register.
+ */
+#define TIMER_LOAD     0x00                    /* ACVR rw */
+#define TIMER_VALUE    0x04                    /* ACVR ro */
+#define TIMER_CTRL     0x08                    /* ACVR rw */
+#define TIMER_CTRL_ONESHOT     (1 << 0)        /*  CVR */
+#define TIMER_CTRL_32BIT       (1 << 1)        /*  CVR */
+#define TIMER_CTRL_DIV1                (0 << 2)        /* ACVR */
+#define TIMER_CTRL_DIV16       (1 << 2)        /* ACVR */
+#define TIMER_CTRL_DIV256      (2 << 2)        /* ACVR */
+#define TIMER_CTRL_IE          (1 << 5)        /*   VR */
+#define TIMER_CTRL_PERIODIC    (1 << 6)        /* ACVR */
+#define TIMER_CTRL_ENABLE      (1 << 7)        /* ACVR */
 
-#define TIMER_INTCLR   0x0c
-#define TIMER_RIS      0x10
-#define TIMER_MIS      0x14
-#define TIMER_BGLOAD   0x18
+#define TIMER_INTCLR   0x0c                    /* ACVR wo */
+#define TIMER_RIS      0x10                    /*  CVR ro */
+#define TIMER_MIS      0x14                    /*  CVR ro */
+#define TIMER_BGLOAD   0x18                    /*  CVR rw */
 
 #endif