[RFC PATCH] irq/mbigen:Fix the problem of IO remap for duplicated physical address in mbigen driver

[majun258@huawei.com (majun (F))]

Hi Mark:

? 2016/2/1 21:25, Mark Rutland ??:
> On Mon, Feb 01, 2016 at 09:06:38PM +0800, majun (F) wrote:
>>
>>
>> ? 2016/2/1 19:57, Mark Rutland ??:
>>> On Mon, Feb 01, 2016 at 07:44:54PM +0800, MaJun wrote:
>>>> From: Ma Jun <majun258@huawei.com>
>>>>
>>>> For mbigen module, there is a special case that more than one mbigen 
>>>> device nodes use the same reg definition in DTS when these devices
>>>> exist in the same mbigen hardware module. 
>>>>
>>>> mbigen_dev1:intc_dev1 {
>>>> 	...
>>>> 	reg = <0x0 0xc0080000 0x0 0x10000>;
>>>> 	...
>>>> };
>>>>
>>>> mbigen_dev2:intc_dev2 {
>>>> 	...
>>>> 	reg = <0x0 0xc0080000 0x0 0x10000>;
>>>> 	...
>>>> };
>>>
>>> This doesn't sound right. If they exist in the same place, and have the
>>> same reg, they _are_ the same device.
>>>
>>> You'll need to explain this better.
>>>
>>
>> For a mbigen hardware module which connecte with several devices,
>> because these devices has different device ID,
>> I need to define a device node for each device in DTS file.
>>
>> 	mbigen
>> 	|
>> ------------------
>> | 	| 	|
>> dev1 	dev2 	dev3
>>
>> Because of register layout,the registers related with these devices
>> are put together, I can't split them clearly.
>> So, I only make these devices which connect with
>> same mbigen hardware module usethe same address.
> 
> This sounds like we've either mis-described the mbigen in the binding,
> or we're mis-describing the relationship with the devices.
> 

Sorry, I didn't express myself clearly.

For example, a mbigen hardware module can support several peripheral devices
with different device ID.

|-----------------------|-
|	mbigen		|
|-----------------------|-
 |       |        |
dev1    dev2     dev3

To simplify the mbigen drvier,
I didn't use the whole mbigen module as a mbgien device, but use
the register collections(vector, trigger type,status etc.) corresponding
to a peripheral device as a mbigen device.
So, mbigen device is a logical conception or logical device.

Now, a mbigen hardware module contains several logical mbigen device.

-------------------------------
|mgn_dev1  mgn_dev2  mgn_dev3 |
|-----------------------------|
   |          |        |
dev1	    dev2      dev3

So,mgn_dev1, mgn_dev2 and mgn_dev3 exist in same mbigen hardware module,
and,they use the same reg address region,that is adress of mbigen hardware module.

For this case, I think the question is can we map an reg address
region more than one time?

Thanks!

> It should not be necessary to describe the same set of registers
> repeatedly.
> 
>>>>  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>>> -	mgn_chip->base = devm_ioremap_resource(&pdev->dev, res);
>>>> +	mgn_chip->base = devm_ioremap(&pdev->dev, res->start, resource_size(res));
>>>
>>> These two behaving differently doesn't seem correct either...
>>
>> The problem is caused by memory region check fail because of
>> duplicated address in devm_ioremap_resource().
> 
> The check is sensible. Using devm_ioremap rather than
> devm_ioremap_resource to avoid the check is not the correct solution.
> 
>> For mbigen special case, there is no necessary to do this check.
> 
> I'm not sure I fully agree.
> 
> Regardless, this is not the right solution; it is fragile at best.
> 
> Thanks,
> Mark.
> 
> .
>