[PATCH 04/10] arm: zynq: Load scu baseaddress at run time

[Michal Simek]

2013/3/26 Rob Herring <robherring2 at gmail.com>:
> On 03/26/2013 05:45 AM, Michal Simek wrote:
>> On 03/25/2013 11:34 PM, Rob Herring wrote:
>>> On 03/25/2013 11:07 AM, Michal Simek wrote:
>>>> 2013/3/25 Rob Herring <robherring2 at gmail.com>:
>>>>> On 03/25/2013 09:51 AM, Michal Simek wrote:
>>>>>> Hi Rob,
>>>>>>
>>>>>> 2013/3/25 Rob Herring <robherring2 at gmail.com>:
>>>>>>> On 03/25/2013 08:53 AM, Michal Simek wrote:
>>>>>>>> Use Cortex a9 cp15 to read scu baseaddress.
>>>>>
>>>>> [...]
>>>>>
>>>>>>>> +static void __init scu_init(void)
>>>>>>>> +{
>>>>>>>> +     unsigned long base;
>>>>>>>> +
>>>>>>>> +     base = scu_a9_get_base();
>>>>>>>> +     zynq_cortex_a9_scu_map.pfn = __phys_to_pfn(base);
>>>>>>>> +     zynq_cortex_a9_scu_map.virtual = base;
>>>>>>>
>>>>>>> You are setting the virtual address to the physical base?
>>>>>>>
>>>>>>>> +     iotable_init(&zynq_cortex_a9_scu_map, 1);
>>>>>>>
>>>>>>> Then creating a static mapping...
>>>>>>>
>>>>>>>> +     scu_base = ioremap(base, zynq_cortex_a9_scu_map.length);
>>>>>>>
>>>>>>> And also a dynamic mapping?
>>>>>>
>>>>>> Yes - exactly.
>>>>>
>>>>> You are simply getting lucky that it works. If the physical address did
>>>>> not happen to be in the vmalloc address region, it would not work. You
>>>>> should not do this because you have an implicit requirement and the
>>>>> code
>>>>> will look broken to anyone that reads it.
>>>>
>>>> yeah correct. I will add there a comment to mentioned that.
>>>
>>> I think leaving the define would be better, but either way is fine.
>>
>> ok. From my point of view is better to keep scu where it is and any
>> early vmalloc
>> allocator will be really helpful. Because there is also early map
>> for early console where virtual addresses are hardcoded.
>> It will be just easier to ask generic code to return base if if you request
>> for size.
>>
>> static unsigned long iomapstart = VMALLOC_END;
>>
>> unsigned long get_iomap_virtbase(unsigned long size)
>> {
>>     iomapstart -= size;
>>     return iomapstart;
>> }
>
> It wouldn't be so simple with page/section alignment requirements and such.

Adding alignment to it is not so hard.


>> Something like this will be helpful and then instead of setup virtual
>> addresses for every static io mapping just to call this function
>> and you will get mapping correct all the time.
>
> If you use DT for core count, then you don't need the static mapping and
> can use ioremap (or of_iomap).

yep but on the other hand I have to be sure that all users
are using proper DTS files. And based on my experience with users
I would rather relate on scu count instead of DT count.

Thanks,
Michal

-- 
Michal Simek, Ing. (M.Eng)
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel - Microblaze cpu - http://www.monstr.eu/fdt/
Maintainer of Linux kernel - Xilinx Zynq ARM architecture
Microblaze U-BOOT custodian and responsible for u-boot arm zynq platform