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<p class="MsoNormal"><span lang="EN-US">Dear audio and gfx stakeholders,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">We hope to add a new interface between audio and gfx driver, for gfx driver to notify audio about HDMI/DP hot-plug and ELD update.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Would you please share some comments on the proposal below?
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Background of this issue: On Intel Haswell/Broadwell platforms, there is a HW restriction that after the display HD-Audio controller is in D3,
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">it cannot be waken up by HDMI/DP hot-plug. Consequently, although the gfx driver can still detect the HDMI/DP hot-plug,
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">audio driver has no idea about this and cannot notify user space whether the external HDMI/DP monitor is available for audio playback,
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">because the audio controller cannot wake up to D0 and receive HW unsolicited event about hot-plug from the audio codec.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">This limitation will affect user space to decide whether we can output audio over HDMI/DP.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">To solve the above limitation, Takashi suggested to add a new communication interface between audio and gfx driver: create a common object<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">containing the ops registered by both graphics and audio drivers, then communicate through it, something like vga_switcheroo.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Is it okay to create this kernel object in i915 driver?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I915 can export an API like “display_register_audio_client” for audio driver to register a client and hot-plug notification ops.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I915 can also call some API like “display_register_gfx_client” itself and register ops for audio driver to query monitor presence and ELD info on a specific port.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">It would be faster for audio driver than quering ELD by command/response over the HD-A bus, thus avoid delay in i915 mode set.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">This will also avoid waking up the audio devices unnecessarily if the user space does not really want to use HDMI/DP for audio playback.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Whenever i195 enables/disables audio on a port in modeset, it can call some API like “display_set_audio_state()” on this kernel object and trigger notifications to the audio driver.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">When the audio driver is probed (in the delayed probe stage), it can request i915 API symbol to register the audio client for this communication kernel object.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Since the 1<sup>st</sup> i915 mode set may happen before audio driver registers the ops, we’ll let audio driver check ELD once after registering the audio client ops.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">And for the platforms which uses this communication interface, we can disable unsolicited event for HDMI/DP hot-plug in the audio driver.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">We hope to hear your feedback and start to work out more details.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Thanks & Best Regards<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Mengdong<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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