| Message ID | 1438560441-28739-1-git-send-email-sjg@chromium.org |
|---|---|
| State | Accepted |
| Delegated to: | Simon Glass |
| Headers | show |
On 2 August 2015 at 18:07, Simon Glass <sjg@chromium.org> wrote: > Enable the debug UART and emit a single 'a' early in the init sequence to > show that it is working. > > Unfortunately the debug UART implementation needs a stack to work. I cannot > seem to remove this limitation as the absolute 'jmp %eax' instruction goes > off into the weeds. > > So this means that the character output cannot be any earlier than > car_init_ret, where memory is available for a stack. > > Signed-off-by: Simon Glass <sjg@chromium.org> > Reviewed-by: Lukasz Majewski <l.majewski@samsung.com> > --- > > Changes in v2: > - Put the debug UART setup code in comments since we don't always want it > > arch/x86/cpu/start.S | 9 +++++++++ > configs/minnowmax_defconfig | 4 ++++ > 2 files changed, 13 insertions(+) Applied to u-boot-dm.
diff --git a/arch/x86/cpu/start.S b/arch/x86/cpu/start.S index fdef2bb..ac711ed 100644 --- a/arch/x86/cpu/start.S +++ b/arch/x86/cpu/start.S @@ -128,6 +128,15 @@ car_init_ret: andl $0xfffffff0, %esp post_code(POST_START_STACK) + /* + * Debug UART is available here although it may not be plumbed out + * to pins depending on the board. To use it: + * + * call debug_uart_init + * mov $'a', %eax + * call printch + */ + /* Zero the global data since it won't happen later */ xorl %eax, %eax movl $GENERATED_GBL_DATA_SIZE, %ecx diff --git a/configs/minnowmax_defconfig b/configs/minnowmax_defconfig index e98f5eb..a67597d 100644 --- a/configs/minnowmax_defconfig +++ b/configs/minnowmax_defconfig @@ -24,3 +24,7 @@ CONFIG_FRAMEBUFFER_VESA_MODE_11A=y CONFIG_DM_RTC=y CONFIG_USE_PRIVATE_LIBGCC=y CONFIG_SYS_VSNPRINTF=y +CONFIG_DEBUG_UART=y +CONFIG_DEBUG_UART_NS16550=y +CONFIG_DEBUG_UART_BASE=0x3f8 +CONFIG_DEBUG_UART_CLOCK=1843200