at91: Add arch_preboot_os which disables PIT in a faster way

When disabled the PIT runs until it reaches the CPIV value.
The Linux PIT driver stops the PIT and waits until it stopped. This can
take over 100ms. Simply stopping in u-boot isn't sufficient as the PIT
will still be running when Linux is waiting until it stopped.
So, we stop it in u-boot by setting the compare value to a value slightly
greater than the current running counter to make the PIT stopped in short
time.

Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>

diff --git a/arch/arm/cpu/arm926ejs/at91/cpu.c b/arch/arm/cpu/arm926ejs/at91/cpu.c
index 087fe95179ee9f008f361eaa81f909a784a1ddc6..5e30f1dccc41496e47bf71d0c42f7dad7ab6f696 100644 (file)
--- a/arch/arm/cpu/arm926ejs/at91/cpu.c
+++ b/arch/arm/cpu/arm926ejs/at91/cpu.c
@@ -27,6 +27,7 @@
 
 #include <asm/arch/hardware.h>
 #include <asm/arch/at91_pmc.h>
+#include <asm/arch/at91_pit.h>
 #include <asm/arch/at91_gpbr.h>
 #include <asm/arch/clk.h>
 #include <asm/arch/io.h>
@@ -40,6 +41,21 @@ int arch_cpu_init(void)
        return at91_clock_init(CONFIG_SYS_AT91_MAIN_CLOCK);
 }
 
+void arch_preboot_os(void)
+{
+       ulong cpiv;
+       at91_pit_t *pit = (at91_pit_t *) AT91_PIT_BASE;
+
+       cpiv = AT91_PIT_MR_PIV_MASK(readl(&pit->piir));
+
+       /*
+        * Disable PITC
+        * Add 0x1000 to current counter to stop it faster
+        * without waiting for wrapping back to 0
+        */
+       writel(cpiv + 0x1000, &pit->mr);
+}
+
 #if defined(CONFIG_DISPLAY_CPUINFO)
 int print_cpuinfo(void)
 {