On 07/20/2012 01:44 PM, RAHUL SHARMA wrote: > > On Fri, Jul 20, 2012 at 11:40 AM, RAHUL SHARMA <rahul.sharma at samsung.com> > wrote: >> >> >> ------- Original Message ------- >> Sender : Lars-Peter Clausen<lars at metafoo.de> >> Date : Jul 19, 2012 19:12 (GMT+05:30) >> Title : Re: exynos drm hdmi audio: how to recieve audio parameters (sf, bps, >> channel count) >> >> On 07/19/2012 02:22 PM, Rob Clark wrote: >>> On Tue, Jul 17, 2012 at 1:12 AM, RAHUL SHARMA wrote: >>>> hi, >>>> >>>> I am adding support for hdmi audio, inside exynos drm hdmi driver. Hdmi >>>> audio is initialized with default parameters. I want to implement the >>>> mechanism to update hdmi registers, whenever audio properties got changed >>>> (i2s/spdif). raedon/r600 drm dirver is polling the audio ip every 100 ms >>>> and reconfigure the hdmi audio block. This is not possible with exynos as >>>> all information cannot be collected from i2s tx registers. It is directly >>>> set on wm8994 connected through i2c. >>>> Possible solution: >>>> 1) drm driver exposing ioctl for setting audio parameters. >>>> 2) alsa driver notifying the change in audio parameters through kernel >>>> notifiers. drm hdmi driver subscribed for the same. >>> >>> I am certainly not an audio expert, but I am pretty sure something >>> along the lines of solution #2 would be better. I don't think >>> userspace would want to know about some exynos drm specific ioctls in >>> order to make audio work. >>> >>> BR, >>> -R >> >> >> I don't know how the audio setup for exynos HDMI hardware looks like, so >> this might not be applicable in this case. But what I did for HDMI >> transmitter I was working on, is to register a ASoC codec device as a >> subdevice to the HDMI transmitter. All access to the sound registers is done >> from that subdevice and you don't need any special notifier hooks, since you >> can use the normal alsa driver callbacks. >> >> It might be a good idea if you could describe how your setup looks exactly. >> E.g. which components does the audio stream pass through, where does it >> originate and how the different components related to each other. >> >> - Lars > > Thanks Lars, Rob, Kyungmin, > > In exynos, i2s and spdif DAIs configure the i2s, spdif tx IP regs. In hw, I2s > and > spdif tx o/p pins are also connected to the i2s-In and spdif-In blocks of > hdmi tx. > Drm hdmi sub driver needs to configure the i2s-In and spdif-In blocks with the > same setting as in i2s and spdif tx IPs. Hdmi is solely accessed by drm driver > where hdmi is registered as a sub-driver along with lcd sub-driver. I hope, I > am > able to explain the flow and connections, through above.
With this setup, I think, implementing the HDMI audio as a ASoC codec driver is the right approach. > > Lars, how can I refer your implementation where Adding 'hdmi audio' as a > seperate > subdrv. If I understand correctly, it will be exposed as a seperate sound > card, > parallel to i2s and spdif cards, which user app accesses and configure and > about > scenarios with hpd. With ASoC you can build complex sound card consisting out of multiple components. E.g. SPDIF DAI + HDMI codec is a sound card and the settings applied to that sound card will be send to both the SPDIF DAI and the HDMI codec, so you can be sure that both have a matching config. You need to have a ASoC board driver though which describes how DAI and codec are interconnected, but you'll need that anyway to get a sound card for the SPDIF controller instantiated, so that should not be a problem. > > Kyungmin, about adding ioctl; it looks clean, but as Rob stated, is it a > right way as drm > framework is primarily meant for gfx/video configurations? Please exaplin me > this point. >From a technical point of view using a custom IOCTL for this is a bad idea, since you'll require special tools to make sound over HDMI work, while by using the method described above the standard tools will work out of the box. - Lars
