[PATCH 09/13] syscon: Probe device first in syscon_get_regmap

[Jonas Karlman]

Hi Jiaxun,

On 2024-05-15 02:12, Jiaxun Yang wrote:
> 
> 
> 在2024年5月14日五月 下午3:50，Jonas Karlman写道：
>> Hi Jiaxun,
> [...]
>>> +		return ERR_PTR(ret);
>>
>> Please explain in more details what the issue this is trying to solve.
>>
>> Typically syscon_get_regmap() is called on a udevice returned from a
>> uclass_get_device call, and that should trigger a probe for the device
>> and its parents.
>>
>> Adding device_probe() here possible just hides an issue that exists
>> somewhere else. In what instance are you ending up with a call to
>> this function with a udevice that has not been probed?
> 
> Hi Jonas,
> 
> Thanks for the reply, my problem is in [PATCH 10/13] I'm using dev->parent
> directly to get parent device and then use that pointer to access
> syscon_get_regmap.

Looking at the driver model lifecycle docs and the clk_boston driver I
would suggest you to change from using the of_to_plat() ops and do same
in probe() ops instead.

That way your parent udevice will have been probed and you do not need
to manually probe it at of_to_plat() stage.

https://docs.u-boot.org/en/latest/develop/driver-model/design.html#driver-lifecycle

"""
If your device relies on its parent setting up a suitable address space,
so that dev_read_addr() works correctly, then make sure that the parent
device has its setup code in of_to_plat(). If it has it in the probe
method, then you cannot call dev_read_addr() from the child device's
of_to_plat() method. Move it to probe() instead.
"""

Moving your syscon_get_regmap() call from of_to_plat() to probe() should
make this syscon patch unnecessary.

Regards,
Jonas

> 
> There is no chance to invoke uclass_get_device_* as what we need is just
> the parent device.
> 
> I can think of two solution without touching syscon code here.
> 
> First would be performing uclass_get_device_by_ofnode against parent's
> ofnode, which seems a little bit overkilling.
> 
> Second would be trigger probing in dev_get_parent.
> 
> Thanks
> - Jiaxun
> 
>>
>> Also, please add a new test to test/dm/regmap.c if this solves a real
>> issue.
>>
>> Regards,
>> Jonas
>>
>>>  	priv = dev_get_uclass_priv(dev);
>>>  	return priv->regmap;
>>>  }
>>>
>