>>>>> "Felipe" == Felipe Balbi <balbi@xxxxxx> writes:
Hi,
>> > +++ b/arch/arm/mach-omap2/omap_hwmod_33xx_data.c
>> > @@ -992,7 +992,7 @@ static struct omap_hwmod am33xx_gpio1_hwmod = {
>> > .name = "gpio2",
>> > .class = &am33xx_gpio_hwmod_class,
>> > .clkdm_name = "l4ls_clkdm",
>> > - .flags = HWMOD_CONTROL_OPT_CLKS_IN_RESET,
>> > + .flags = (HWMOD_INIT_NO_IDLE | HWMOD_INIT_NO_RESET),
>> > .mpu_irqs = am33xx_gpio1_irqs,
>> > .main_clk = "l4ls_gclk",
>> > .prcm = {
>> >
>> > Now the question is why is this configured like this?
>>
>> This behavior is intended to decouple the kernel from the bootloader, or
>> previously-booted operating system (e.g., the kexec case). The original
>> goal was to place the system in an known safe state as soon as possible
>> after the kernel starts. This is to prevent misconfigured or
Felipe> there is one "issue" with this. At least on AM335x starter kit,
Felipe> GPIO0_7 is used as DDR power pin. If we reset that GPIO bank,
Felipe> DDR looses power and "for obscure reasons" (:-)) the board
Felipe> doesn't boot.
Heh!
Felipe> In this case, we cannot reset that bank, otherwise Starter Kit
Felipe> will never boot in mainline. Bad PCB design, I know, but it's
Felipe> not something we can change now :-)
Indeed. So that's two examples of people designing boards with the
assumption that gpios will not toggle between bootloader and running
system. Chances are that there will be others.
--
Bye, Peter Korsgaard
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