On 05/13/2013 03:50 PM, Wang, Xingchao wrote: >> -----Original Message----- >> From: David Henningsson [mailto:david.henningsson at canonical.com] >> Sent: Monday, May 13, 2013 8:13 PM >> To: Wang, Xingchao >> Cc: Wang Xingchao; alsa-devel at alsa-project.org; daniel at ffwll.ch; >> tiwai at suse.de; Lin, Mengdong; intel-gfx at lists.freedesktop.org; Li, Jocelyn; >> Barnes, Jesse; Girdwood, Liam R; Zanoni, Paulo R >> Subject: Re: [alsa-devel] [PATCH 5/5] ALSA/i915: Check power well API >> existense before calling >> >> On 05/13/2013 01:55 PM, Wang, Xingchao wrote: >>> Hi David, >>> >>> >>>> -----Original Message----- >>>> From: alsa-devel-bounces at alsa-project.org >>>> [mailto:alsa-devel-bounces at alsa-project.org] On Behalf Of David >>>> Henningsson >>>> Sent: Monday, May 13, 2013 4:29 PM >>>> To: Wang Xingchao >>>> Cc: alsa-devel at alsa-project.org; daniel at ffwll.ch; tiwai at suse.de; Lin, >>>> Mengdong; intel-gfx at lists.freedesktop.org; Li, Jocelyn; Barnes, >>>> Jesse; Girdwood, Liam R; Zanoni, Paulo R >>>> Subject: Re: [alsa-devel] [PATCH 5/5] ALSA/i915: Check power well API >>>> existense before calling >>>> >>>> On 05/13/2013 09:37 AM, Wang Xingchao wrote: >>>>> I915 module maybe loaded after snd_hda_intel, the power-well API >>>>> doesnot exist in such case. This patch intended to avoid loading >>>>> dependency between snd-hda-intel and i915 module. >>>> >>>> Hi Xingchao and thanks for working on this. >>>> >>>> This patch seems to re-do some of the work done in other patches (a >>>> lot of lines removed), so it's a little hard to follow. But I'll try >>>> to write some overall comments on how I have envisioned things... >>>> >>>> 1. I don't think there's any need to create an additional kernel >>>> module, we can just let hda_i915.c be in the snd-hda-intel.ko module, >>>> and only compile it if >>>> DRM_I915 is defined. >>>> >>>> 2. We don't need an IS_HSW macro on the audio side. Instead declare a >>>> new AZX_DCAPS_NEED_I915_POWER (or similar) driver quirk. >>>> >>>> 3. Somewhere in the beginning of the probing in hda_intel.c, we'll >>>> need something like: >>>> >>>> if (driver_caps & AZX_DCAPS_NEED_I915_POWER) >>>> hda_i915_init(chip); >>>> >>>> 4. The hda_i915_init does not need to be exported (they're now both >>>> in the same module). hda_i915.h could have something like: >>>> >>>> #ifdef DRM_I915 >>>> void hda_i915_init(chip); >>>> #else >>>> #define hda_i915_init(chip) do {} while(0) #endif >> >> Or perhaps even better >> >> static inline void hda_i915_init(azx *chip) {} >> >>> >>> Thanks your suggestions. Will change them in next version. >>>> >>>> 5. You're saying this patch is about avoid loading dependency between >>>> snd-hda-intel and i915 module. That does not make sense to me, since >>>> the powerwell API is in the i915 module, snd-hda-intel must load it >>>> when it wants to enable power on haswell, right? Thus there is a >>>> loading dependency. If the i915 module is not loaded at that point, >>>> we must wait for it to load, so we can have proper power, instead of >> continuing probing without the power well? >>>> >>> >>> If i915 module not loaded, snd-had-intel will load it in current code. >>> The question is the tolerant delay of waiting for i915 loading. >> >> Could you explain in more detail, what you mean with "tolerant delay" >> and what will happen if you exceed that delay? > > You said " If the i915 module is not loaded at that point, we must wait for it to load". > I'm not clear about the routine, how long will snd-hda-intel wait? What would happen if loading i915 too long time? > How will snd-hda-intel get to know the i915 loading finished? I'm not experienced in module loading either, but I believe "request_module" load the i915 driver and not return until i915 has finished loading? Note: You should get rid of the backwards reference (as Jaroslav pointed out), because not only is it not needed, it could potentially cause a deadlock if the i915 and snd-hda-intel modules both try to load each other. -- David Henningsson, Canonical Ltd. https://launchpad.net/~diwic
