On Wed, Oct 23, 2013 at 09:42:06PM +0300, Jani Nikula wrote: > On Wed, 23 Oct 2013, Paulo Zanoni <przanoni@xxxxxxxxx> wrote: > > 2013/10/23 Ben Widawsky <ben@xxxxxxxxxxxx>: > >> On Mon, Oct 21, 2013 at 11:56:09AM -0200, Paulo Zanoni wrote: > >>> From: Paulo Zanoni <paulo.r.zanoni@xxxxxxxxx> > >>> > >>> The audio driver uses the power well provided by our driver, so on > >>> Haswell we can't "rmmod i915" if we don't "rmmod snd_hda_intel" first. > >>> > >>> The problem with removing snd_hda_intel is that we also need to kill > >>> its users. On the specific machine I tested, the only user seem to be > >>> alsactl, but on other machines this may change. IMHO we should leave > >>> the "kill user space" step to whoever is running the script, but > >>> Daniel asked me to put it here so we have a better chance of Just > >>> Working on QA's machines. > >>> > >>> Signed-off-by: Paulo Zanoni <paulo.r.zanoni@xxxxxxxxx> > >>> --- > >>> tests/module_reload | 6 ++++++ > >>> 1 file changed, 6 insertions(+) > >>> > >>> diff --git a/tests/module_reload b/tests/module_reload > >>> index 3d8cb85..c1fd395 100755 > >>> --- a/tests/module_reload > >>> +++ b/tests/module_reload > >>> @@ -18,6 +18,10 @@ if ! echo 0 > /sys/class/vtconsole/vtcon1/bind ; then > >>> exit 77 > >>> fi > >>> > >>> +# The sound driver uses our power well > >>> +pkill alsactl > >>> +rmmod snd_hda_intel &> /dev/null > >>> + > >>> #ignore errors in ips - gen5 only > >>> rmmod intel_ips &> /dev/null > >>> rmmod i915 > >>> @@ -38,6 +42,8 @@ fi > >>> modprobe i915 > >>> echo 1 > /sys/class/vtconsole/vtcon1/bind > >>> > >>> +modprobe snd_hda_intel > >>> + > >>> # try to run something > >>> $SOURCE_DIR/gem_exec_nop > /dev/null && echo "module successfully loaded again" > >>> > >> > >> I don't really pretend to understand how module dependencies are > >> calculated. However, I would think the dependency should be *somewhere* > >> and so modprobe -r i915 should work. > > > > It's the opposite: "modprobe -r i915" will remove drm.ko, > > drm_kms_helper, i2c-algo-bit and video, but won't remove snd_hda_intel > > (and if you don't remove it first, it will complain that i915.ko is > > still in use). > > > >> > >> Don't read that as a nak. Rather, a wtf is with the existing stuff? > > > > I think the dependency is magically tracked by depmod when it sees the > > Audio driver uses a symbol exported by i915.ko. But a "modinfo > > snd_hda_intel" doesn't show i915.ko on the "depends" section, which is > > strange. I'm also not an expert on this area... > > This is because snd_hda_intel does not depend on i915, to make it > possible to use snd_hda_intel without i915. Which makes sense. Instead, > it uses symbol_request() to be able to call a couple of i915 functions > when available. > > I don't know if there's a way to check this runtime dependency from > userspace. But obviously you can't remove i915 while snd_hda_intel holds > function pointers to i915. (In fact, intel_ips is the same.) > > BR, > Jani. > > > -- > Jani Nikula, Intel Open Source Technology Center Looking around it seems a fairly common idiom is to do the symbol_(get|request) when you need to call the function, and release it when you're no longer using it. Since these functions we're talking about require waking the GPU, I think speed shouldn't be a concern. As you say, it makes sense to be able to load audio without i915 - however looking at the code, it seems like audio will fail if i915 is not loaded. Also, it looks like there should be a way to make userspace aware of the dependency since it calls back in to userspace (I find it funny that the name of the function uses 4 underscores: ____call_usermodehelper). -- Ben Widawsky, Intel Open Source Technology Center _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
