[Adding Marek]

On Tue, Sep 10, 2019 at 5:32 AM Rasmus Villemoes rasmus.villemoes@prevas.dk wrote:

It's true that booting normally doesn't take long enough for the register to roll (which actually happens in a little over an hour, not just a few seconds). However, the counter starts at power-on, and if the board is held in reset to be booted over USB, one actually risks hitting wrap-around during boot, which can both result in too short delays (if the "st += delay" calculation makes st small) and theoretically also unbound delays (if st ends up being UINT_MAX and one just misses sampling digctl_microseconds at that point).

It doesn't take more code to DTRT, and once bitten, twice shy.

Signed-off-by: Rasmus Villemoes rasmus.villemoes@prevas.dk

arch/arm/cpu/arm926ejs/mxs/spl_boot.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/arch/arm/cpu/arm926ejs/mxs/spl_boot.c b/arch/arm/cpu/arm926ejs/mxs/spl_boot.c index cb361ac65c..336266fe82 100644 --- a/arch/arm/cpu/arm926ejs/mxs/spl_boot.c +++ b/arch/arm/cpu/arm926ejs/mxs/spl_boot.c @@ -24,9 +24,7 @@ static bd_t bdata __section(".data");

/*

• This delay function is intended to be used only in early stage of boot, where

• • clock are not set up yet. The timer used here is reset on every boot and
• • takes a few seconds to roll. The boot doesn't take that long, so to keep the
• • code simple, it doesn't take rolling into consideration.

• • clock are not set up yet.
  */

void early_delay(int delay) { @@ -34,8 +32,7 @@ void early_delay(int delay) (struct mxs_digctl_regs *)MXS_DIGCTL_BASE;

    uint32_t st = readl(&digctl_regs->hw_digctl_microseconds);

•   st += delay;
  

•   while (st > readl(&digctl_regs->hw_digctl_microseconds))
  

•   while (readl(&digctl_regs->hw_digctl_microseconds) - st <= delay)
            ;
  

Looks reasonable for me.

Thanks