Hi Simon, On Mon, Sep 3, 2018 at 7:02 AM Simon Glass <s...@chromium.org> wrote: > > In initr_bootstage() we call bootstage_mark_name() which ends up calling > timer_get_us(). This call happens before initr_dm(), which inits driver > model. > > On x86 we set gd->timer to NULL in the transition from board_init_f()
It's not just x86 we set gd->timer to NULL. It applied to all architectures when CONFIG_TIMER is on. > to board_init_r(). See board_init_f_r() for this assignment. So U-Boot > knows there is no timer available in the period immediately after > relocation. > > On x86 the timer_get_us() call is implemented as calls to get_ticks() and > get_tbclk(). Both of these call dm_timer_init() to set up the timer, if > gd->timer is NULL and the early timer is not available. > > However dm_timer_init() cannot succeed before initr_dm() is called. > > So it seems that on x86 if we want to use CONFIG_BOOTSTAGE we must enable > CONFIG_TIMER_EARLY. Update the Kconfig to handle this. > > Note: On most architectures we can rely on the pre-relocation memory still > being available, so that gd->timer pointers to a valid timer device and > everything works correctly. Admittedly this is not strictly correct since > the timer device is set up by pre-relocation U-Boot, but normally this is > fine. On x86 the 'CAR' (cache-as-RAM) memory used by pre-relocation U-Boot > disappears in board_init_f_r() and any attempt to access it will hang. > This is the reason why we must mark the timer as invalid when we get to > board_init_f_r(). > > Signed-off-by: Simon Glass <s...@chromium.org> > --- > > drivers/timer/Kconfig | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/timer/Kconfig b/drivers/timer/Kconfig > index 5ab6749193c..ff434de6f7c 100644 > --- a/drivers/timer/Kconfig > +++ b/drivers/timer/Kconfig > @@ -30,6 +30,9 @@ config TPL_TIMER > config TIMER_EARLY > bool "Allow timer to be used early in U-Boot" > depends on TIMER > + # initr_bootstage() requires a timer and is called before initr_dm() > + # so only the early timer is available > + default y if X86 && BOOTSTAGE Since this applies not only on x86, and given without TIMER_EARLY BOOTSTAGE is broken, shouldn't we do this in BOOTSTAGE config instead: config BOOTSTAGE select TIMER_EARLY > help > In some cases the timer must be accessible before driver model is > active. Examples include when using CONFIG_TRACE to trace U-Boot's > -- Regards, Bin _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot