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From: Clemens Ladisch <clemens@ladisch.de>
To: "Deucher, Alexander" <Alexander.Deucher@amd.com>,
	Dagg Stompler <daggs@gmx.com>
Cc: "alsa-user@lists.sourceforge.net"
	<alsa-user@lists.sourceforge.net>,
	"alsa-devel@alsa-project.org" <alsa-devel@alsa-project.org>
Subject: Re: [Alsa-user]  hdmi sound rerouted?
Date: Mon, 30 Sep 2013 09:05:25 +0200	[thread overview]
Message-ID: <524922B5.6070305@ladisch.de> (raw)
In-Reply-To: <A3397C8B8B789E45844E7EC5DEAD89D02E80B231@satlexdag05.amd.com>

Deucher, Alexander wrote:
>> Even the latest driver lacks the PCI IDs of many HDMI HDA devices
>> (aa50/aa58/aa60/aa68/aa80/aa88/aa90/aa98: Cypress/Juniper/Redwood/Cedar/
>> Cayman+Antilles/Barts/Turks/Caicos).
>>
>> Alex, are these devices that require disabling snooping?
>
> Sorry what does snooping mean in this context?

Coherent memory accesses, i.e., not setting bit 18 in the stream
descriptor control register; the HDA spec says:
| Traffic Priority (TP):  If set to a 1, the stream will be treated as
| preferred traffic if the underlying bus supports it.  If set to a 0,
| the traffic will be handled on a “best effort” basis.  [...]
| On PCI Express, for example, setting the TP bit to a 1 might cause
| the controller to generate non-snooped isochronous traffic, while
| a PCI implementation may ignore this bit.
| It is permitted to implement this bit as RO if there is no
| controllability available.

So "require" might be wrong, this is just an optimization.  Anyway,
devices up to aa48 use snooping, while from aaa0 (Tahiti XT) forward,
the driver sets TP (<http://git.kernel.org/linus/1815b34a6267>).
The question is, what was the first device to support this?


Regards,
Clemens
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  reply	other threads:[~2013-09-30  7:05 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20130927185045.47660@gmx.com>
2013-09-28 22:32 ` [alsa-devel] hdmi sound rerouted? Clemens Ladisch
2013-09-30  2:23   ` [Alsa-user] " Deucher, Alexander
2013-09-30  7:05     ` Clemens Ladisch [this message]
2013-09-30  9:18     ` Takashi Iwai
2013-10-07 13:36       ` Deucher, Alexander
2013-10-08  7:49         ` Takashi Iwai
2013-10-19  9:49 [alsa-devel] " Dagg Stompler
2013-10-19 12:59 ` [Alsa-user] " Deucher, Alexander
  -- strict thread matches above, loose matches on Subject: below --
2013-11-03  7:50 Dagg Stompler
2013-11-04  8:43 ` Takashi Iwai
2013-11-04 12:21 daggs
2013-11-04 13:04 ` Takashi Iwai
2013-11-04 13:47   ` Deucher, Alexander
2013-11-04 14:06     ` Takashi Iwai
2013-11-04 18:53 Dagg Stompler
2013-11-05  7:14 ` Takashi Iwai
2013-11-05  8:27   ` Clemens Ladisch
2013-11-05  8:49     ` Takashi Iwai
2013-11-05  9:49 Dagg Stompler

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