Re: Problems loading firmware using built-in drivers with kernels that use initramfs.

[Arend van Spriel]

On 08/29/2015 09:11 AM, Takashi Iwai wrote:
> On Sat, 29 Aug 2015 06:09:01 +0200,
> Ming Lei wrote:
> > On Sat, Aug 29, 2015 at 9:11 AM, Luis R. Rodriguez <mcgrof@xxxxxxxx> wrote:
> > > On Thu, Aug 27, 2015 at 08:55:13AM +0800, Ming Lei wrote:
> > > > On Thu, Aug 27, 2015 at 2:07 AM, Linus Torvalds
> > > > <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> > > > > On Wed, Aug 26, 2015 at 1:06 AM, Liam Girdwood
> > > > > <liam.r.girdwood@xxxxxxxxxxxxxxx> wrote:
> > > > > > I think the options are to either :-
> > > > > >
> > > > > > 1) Don not support audio DSP drivers using topology data as built-in
> > > > > > drivers. Audio is not really a critical system required for booting
> > > > > > anyway.
> > > > >
> > > > > Yes, forcing it to be a module and not letting people compile it in by
> > > > > mistake (and then not have it work) is an option.
> > > > >
> > > > > That said, there are situations where people don't want to use
> > > > > modules. I used to eschew them for security reasons, for example - now
> > > > > I instead just do a one-time temporary key. But others may have other
> > > > > reasons to try to avoid modules.
> > > > >
> > > > > > 2) Create a default PCM for every driver that has topology data on the
> > > > > > assumption that every sound card will at least 1 PCM. This PCM can then
> > > > > > be re-configured when the FW is loaded.
> > > > >
> > > > > That would seem to be the better option if it is reasonably implementable.
> > > > >
> > > > > Of course, some kind of timer-based retry (limited *somehow*) of the
> > > > > fw loading could work too, but smells really really hacky.
> > > >
> > > > Yeah, years ago, we discussed to use -EPROBE_DEFER for the situation,
> > > > which should be one kind of fix, but looks there were objections at that time.
> > >
> > > That would still be a hack. I'll note there is also asynchronous probe support
> > > now but to use that would also be a hack for this issue. We don't want to
> >
> > If we think firmware as one kind of resources like regulators, gpio and others,
> > PROBE_DEFER is one good match for firmware loading case, and
> > it has been used by lots of drivers, so why can't it be used for
> > firmware loading?
> >
> > One problem is that we need to convert drivers into returning -EPROBE_DEFER
> > in case of request failure, and that may involve some work, but which
> > should be mechanical.
>
> I find such a delaying mechanism not so bad, too.  It's very
> straightforward, at least, no big pain in the transition in the driver
> side.

Not sure how this is going to work with request_firmware_nowait(). We 
use that in our drivers to get rid of ~60 sec. delay in probe and 
consequently boot time when built-in. So basically we return 0 on probe 
lacking better knowledge. Guess we can always move back to 
request_firmware calls when defer_probe support is available.

Regards,
Arend

> > > encourage folks to go down that road.  They'd be hacks for this issue as you
> > > are simply delaying the driver probe for a later time and there is no guarantee
> > > that any pivot_root() might have already been completed later to ensure your
> > > driver's fw file is present. So it may work or it may not.
> >
> > We can trigger defer probe explicitly once root fs is setup or other condition
> > is met.
>
> Right, how to trigger the reprobe (and relevant optimization) needs to
> be considered on top of the current mechanism.
>
>
> Takashi
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