[U-Boot] [PATCH v2 18/26] dm: usb: Remove inactive children after a bus scan

[Hans de Goede]

Hi,

On 11/13/2015 10:58 PM, Simon Glass wrote:
> Hi Hans,

<snip>

>>>> Talking about usb-stop, there is still one (BIG!) problem after
>>>> this patch set when building usb-support with DM_DEVICE_REMOVE
>>>> not set. This means that the controllers dma engines will not
>>>> be stopped when booting the actual OS and they will still be
>>>> accessing parts of the main memory while the actual OS is
>>>> booting, which is BAD. So I suggest adding something like
>>>> this to all host drivers which use dma in this way:
>>>>
>>>> #if defined CONFIG_DM_USB && !defined CONFIG_DM_DEVICE_REMOVE
>>>> #error The EHCI driver cannot be used without CONFIG_DM_DEVICE_REMOVE
>>>> otherwise DMA stays active while booting the OS
>>>> #endif
>>>
>>>
>>> Sounds good. I am not suggesting that we encourage people to build USB
>>> with out DM_DEVICE_REMOVE. I just want to make sure that we don't
>>> create unnecessary dependencies such that DM_DEVICE_REMOVE becomes
>>> impossible to use.
>>>
>>> We have a note in the Kconfig for that, but I agree we need to make it
>>> more explicit. With the #if approach it makes the pitfall much more
>>> obvious.
>>
>>
>> Ack, so we need to have patches for this for at least ohci, ehci, xhci
>> and I guess also uhci ? Who is going to write these patches ?
>
> I suppose I could do that. I would like to make sure that any USB fish
> hooks are removed, and that is part of the solution.
>
> I'd really like to resolve this and move things forward. If you still
> have have strong objections please let me know.

There are no objections from my side to move forward with your current
solution.

> We did discuss this at
> the time and I was clear that I did not want to keep the solution as
> it was - I merged it because it fixed a bug, as you pointed out at the
> time.

Ack.

Regards,

Hans