Fix SP804 delay timer on FVP
This patch fixes several issues with the SP804 delay timer on FVP:
* By default, the SP804 dual timer on FVP runs at 32 KHz. In order
to run the timer at 35 MHz (as specified in the FVP user manual)
the Overwrite bit in the SP810 control register must be set.
* The CLKMULT and CLKDIV definitions are mixed up:
delta(us) = delta(ticks) * T(us) = delta(ticks) / f(MHz)
From the delay function:
delta_us = (delta * ops->clk_mult) / ops->clk_div;
Matching both expressions:
1 / f(MHz) = ops->clk_mult / ops->clk_div
And consequently:
f(MHz) = ops->clk_div / ops->clk_mult
Which, for a 35 MHz timer, translates to:
ops->clk_div = 35
ops->clk_mult = 1
* The comment in the delay timer header file has been corrected:
The ratio of the multiplier and the divider is the clock period
in microseconds, not the frequency.
Change-Id: Iffd5ce0a5a28fa47c0720c0336d81b678ff8fdf1
diff --git a/plat/arm/board/fvp/fvp_bl2_setup.c b/plat/arm/board/fvp/fvp_bl2_setup.c
index b1cdef4..305309a 100644
--- a/plat/arm/board/fvp/fvp_bl2_setup.c
+++ b/plat/arm/board/fvp/fvp_bl2_setup.c
@@ -28,6 +28,7 @@
* POSSIBILITY OF SUCH DAMAGE.
*/
+#include <mmio.h>
#include <plat_arm.h>
#include <sp804_delay_timer.h>
#include <v2m_def.h>
@@ -47,6 +48,10 @@
{
arm_bl2_platform_setup();
+ /* Enable the clock override for SP804 timer 0, which means that no
+ * clock dividers are applied and the raw (35 MHz) clock will be used */
+ mmio_write_32(V2M_SP810_BASE, FVP_SP810_CTRL_TIM0_OV);
+
/* Initialize delay timer driver using SP804 dual timer 0 */
sp804_timer_init(V2M_SP804_TIMER0_BASE,
SP804_TIMER_CLKMULT, SP804_TIMER_CLKDIV);
diff --git a/plat/arm/board/fvp/fvp_def.h b/plat/arm/board/fvp/fvp_def.h
index 3af4db6..41b872a 100644
--- a/plat/arm/board/fvp/fvp_def.h
+++ b/plat/arm/board/fvp/fvp_def.h
@@ -96,8 +96,14 @@
#define PWRC_BASE 0x1c100000
/* FVP SP804 timer frequency is 35 MHz*/
-#define SP804_TIMER_CLKMULT 35
-#define SP804_TIMER_CLKDIV 1
+#define SP804_TIMER_CLKMULT 1
+#define SP804_TIMER_CLKDIV 35
+
+/* SP810 controller. FVP specific flags */
+#define FVP_SP810_CTRL_TIM0_OV (1 << 16)
+#define FVP_SP810_CTRL_TIM1_OV (1 << 18)
+#define FVP_SP810_CTRL_TIM2_OV (1 << 20)
+#define FVP_SP810_CTRL_TIM3_OV (1 << 22)
/*******************************************************************************
* GIC-400 & interrupt handling related constants