[U-Boot] [RFC] Detecting coldstart on kirkwood CPUs

[Simon Kagstrom]

Hi (mostly Prafulla)!

I'm looking at detecting cold starts on the OpenRD board (and also
maintain the bootcounter via this). I've come up with a slight hack
which works in practice for me, but which feels a bit unsafe.

What I do is basically to reset the SYSRST duration counter just before
doing the soft reset in reset_cpu() (see patch below, I do a similar
thing in Linux). I've then added the following function to the board
code:

   #if defined(CONFIG_MISC_INIT_R)
   # define MS_TO_COUNT(x) ( ((x) * 1000 * 1000) / 40)
   int misc_init_r (void)
   {
	   u32 rst_count = 0x1fffffff & readl(KW_REG_SYSRST_CNT);
	   struct uboot_com *p =
			   (struct uboot_com *)CONFIG_BOOTCOUNT_ADDR;

	   /* clear the counter for next valid read*/
	   writel(1 << 31, KW_REG_SYSRST_CNT);

	   /* If the reset has been held for over 20ms it's a cold-start,
	    * wait for 40 to be sure
	    *
	    * FIXME! This should rely one some more safe metric for the future
	    */
	   if ( rst_count > MS_TO_COUNT(40) ) {
		   printf("Start type: cold\n");
		   p->bootcount_magic = 0x12345678; /* Clear the bootcount magic */
		   p->is_coldstart = is_coldstart = 1;
	   } else {
		   printf("Start type: warm\n");
		   p->is_coldstart = is_coldstart = 0;
	   }

	   return 0;
   }
   #endif

i.e., just check how long the reset was held at startup. If it's longer
than an empirically determined value (~40ms), then it's a cold start.
Pressing the reset button, I always get cold starts (even when tapping
as fast as I can), while soft resets are always warm.

But... Isn't there some better way of checking this on Kirkwood?

// Simon

[PATCH] Reset sysrst count before restarting

Signed-off-by: Simon Kagstrom <simon.kagstrom at netinsight.net>
---
 cpu/arm926ejs/kirkwood/cpu.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/cpu/arm926ejs/kirkwood/cpu.c b/cpu/arm926ejs/kirkwood/cpu.c
index bab5faf..d0cdaf6 100644
--- a/cpu/arm926ejs/kirkwood/cpu.c
+++ b/cpu/arm926ejs/kirkwood/cpu.c
@@ -37,6 +37,7 @@ void reset_cpu(unsigned long ignored)
 
 	writel(readl(&cpureg->rstoutn_mask) | (1 << 2),
 		&cpureg->rstoutn_mask);
+	writel(1 << 31, KW_REG_SYSRST_CNT);
 	writel(readl(&cpureg->sys_soft_rst) | 1,
 		&cpureg->sys_soft_rst);
 	while (1) ;
-- 
1.6.0.4