Re: question: How to toggle gpio when init_early

[qianfan <qianfanguijin@163.com>]

在 2022/5/3 7:36, Samuel Holland 写道:
> On 4/28/22 11:30 PM, qianfan wrote:
>> Hi everyone:
>>
>> I want toggle a gpio when machine_desc->init_early, but failed.
>>
>> The gpio is pd24, and I searched the datasheet of r40, the address of PD_DAT
>> register
>> is 0x01c20800 + 3 * 0x24 + 0x10. So I modify this register by __raw_readl and
>> __raw_writel.
>> The system can't startup when I adding those code.
>>
>> Seems the physical address can't touch due to mmu.
>> Can I get some advice?
> You need to call ioremap() to get a virtual address for the MMIO region. But you
I had searched the other mach, some of others has a map_io callback, which
create mmu rules by iotable_init. Copy that idea, I can toggle the gpio
pin.
> really should be using the GPIO API and not raw MMIO. And you really should be
> using devicetree and not touching the machine description. For example, if this
> is for a GPIO-connected watchdog or LED or regulator, Linux already has
> devicetree drivers for these.
Yes, I had enabled the gpio-wdt driver but the sunxi pinctrl/gpio driver
are registed to later. I had sniffer the hardware signals and found it
takes about 3 seconds when gpio-wdt driver ready after u-boot.

sunxi-pinctrl driver are deferred probe and ready when late_init.
Next is the console logs:

[    0.265181] init_late
[    0.293427] sun4i-pinctrl 1c20800.pinctrl: initialized sunXi PIO driver
[    1.760130] gpio_wdt start

So I want add something in machine_desc.

Seems there doesn't has a better way touching gpio watchdog before gpio-wdt
ready.
>
> Regards,
> Samuel