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authorSimon Glass <sjg@chromium.org>2018-09-02 17:02:24 -0600
committerBin Meng <bmeng.cn@gmail.com>2018-10-22 17:51:45 +0800
commit97d20f69f53e7586394e48805f25f23d9a3ebaa8 (patch)
treedfd6112154979d0c3c5ba97b7446fa48d1528f63 /drivers/timer
parent27fb0cf1f0dd061f5a902928417656488db6301f (diff)
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Enable CONFIG_TIMER_EARLY with bootstage
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() 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 <sjg@chromium.org> Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Diffstat (limited to 'drivers/timer')
-rw-r--r--drivers/timer/Kconfig3
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/timer/Kconfig b/drivers/timer/Kconfig
index a7d600b6e4..45a256a35f 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
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