[PATCH v1 2/4] usb: xhci: xhci_mem_init: Use cpu_to_le64() and not xhci_writeq()

[Stefan Roese]

Hi Bin,

On 17.07.20 12:09, Bin Meng wrote:
> Hi Stefan,
> 
> On Fri, Jul 17, 2020 at 6:04 PM Stefan Roese <sr at denx.de> wrote:
>>
>> On 17.07.20 07:24, Bin Meng wrote:
>>> Hi Stefan,
>>>
>>> On Thu, Jul 2, 2020 at 4:47 PM Stefan Roese <sr at denx.de> wrote:
>>>>
>>>> xhci_writeq() makes the CPU->LE swapping only when addressing registers
>>>> in the xHCI controller address range and not in the local memory (RAM).
>>>
>>> Is the above behavior exposed by the MIPS platform's writel()?
>>
>> Not sure what you mean with this. Without this patch, xhci_writeq()
>> will not swap on Octeon MIPS, as the destination address is located
>> in local memory (DDR).
> 
> I wonder why xhci_writeq() does not swap? Is this due to the writel()
> implementation on Octeon MIPS?

Ah, okay. Please see my comment below for this. Here again:

BTW: The Octeon MIPS writel will swap to little-endian, when the
location is in the xHCI controller address space (and PCI etc). This
support for selective swapping is not pushed into mainline yet. I
will send it in some follow up patches.

So to answer your question: writel will not swap when addressing
local memory.

>> Using the xhci_read/write accessor functions
>> should be restricted to accessing the controller registers.
> 
> Yes, this is the supposed usage that xhci_read/write should be called
> to operate on xHCI registers. However my question was why
> xhci_read/write does not swap even it is called on memory space, hence
> the writel() question.
> 
>>
>> BTW: The Octeon MIPS writel will swap to little-endian, when the
>> location is in the xHCI controller address space (and PCI etc). This
>> support for selective swapping is not pushed into mainline yet. I
>> will send it in some follow up patches.
>>
> 
> Regards,
> Bin
> 

Thanks,
Stefan