From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Brown Subject: Re: [PATCH 4/4] ASoc: kirkwood: add DT support Date: Fri, 26 Jul 2013 12:05:54 +0100 Message-ID: <20130726110554.GB9858@sirena.org.uk> References: <20130725111459.145a4aa4@armhf> <20130725191905.GR9858@sirena.org.uk> <20130725230533.GH24642@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="Mq/g1DrVwLsuPImC" Return-path: Content-Disposition: inline In-Reply-To: <20130725230533.GH24642@n2100.arm.linux.org.uk> Sender: linux-kernel-owner@vger.kernel.org To: Russell King - ARM Linux Cc: Jean-Francois Moine , Liam Girdwood , Jaroslav Kysela , Takashi Iwai , Rob Herring , alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org List-Id: alsa-devel@alsa-project.org --Mq/g1DrVwLsuPImC Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Fri, Jul 26, 2013 at 12:05:33AM +0100, Russell King - ARM Linux wrote: > On Thu, Jul 25, 2013 at 08:19:05PM +0100, Mark Brown wrote: > > On Thu, Jul 25, 2013 at 11:14:59AM +0200, Jean-Francois Moine wrote: > > > + if (np) { > > > + priv->burst = 128; /* might be 32 or 128 */ > > > + } else if (data) { > > When you posted this before I queried how and why the value might vary - > > I see the code is the same and I don't recall a reply. > This is the DMA burst size, and can be either 32 or 128 bytes according > to the docs. Everyone seems to pass this as 128 bytes in their platform > data to date, which I guess is why its ended up being hard coded as 128. OK. > However, whether it needs to be configurable or not is debatable - obviously > the hardware allows it, but that doesn't mean it has to be exposed. If > ALSA has some kind of way of specifying a "low latency" mode where 128 > byte vs 32 byte fetches would make a significant difference, then it may > be something to look at. This sort of configuration would normally be keyed off the period size and so vary at runtime depending on what the application does when it opens a stream. Sounds like something someone can worry about if they have the requirement. --Mq/g1DrVwLsuPImC Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.20 (GNU/Linux) iQIcBAEBAgAGBQJR8lgOAAoJELSic+t+oim9NTcQAJAY3wv0YQcp5ZNk3jkW2BO/ aKMHDaysqtwbhoAASzJhVG9WWbld9L+DoevxqhH9lo05+0gA0JOxs7BHG7sLDFqI kvERZ2ZZ4GZ2bySUFhSx09Da89Vi4KEaWwpgF8TUQu72q7JWWj59Q1uEf38XpdHL j3Hr7p2XynbFFsJy3XoMZ1RTuZUGdpkpHRaenPhOojy1pPiseslr/RwAnZSXKuma DVCH9veV9QIKAbVVdC6sRXdidff32JN/pjMcIpTxot5cvwJHMNrzWh2u9SwrqIoE 8x+x5DIRK8ZTAHidKpL+iMYWfvR3dPQxI5VIaWOhbpWEK/zI2H1gMkVS79BAFG4d pOsYLiDmxuWu7ym4OkHOfEuGgjxeRNoSRfOHRnwa6GXZykNhhnU3hxMDc7CbFuKR DxAOdiUpqpeysjH0bx7+kR/08YHVkGa5WEwkCFDcWK/Bm/I38Bv94N3qzUn/VmsS nsbUPc7Hkdd/PD7SSvBqR8tQdtXQ7vl7kzw+AVoW6pbUGHV4sFTVj973MIvWxbLF vE+6ZMNnsI4HRxMOxEhGIaFtzBW9RjTkuLzm4tdcZJQMLZbUJXLZlTlITGLjbRH1 qLtk+ltJfKPpF5Ietu36HZQueuNBZJf+6Et/tfRVCfX4qLnM/Ok2TMnF5P7V/hCD aF7W/WYZWm59Nza5eTie =jF6/ -----END PGP SIGNATURE----- --Mq/g1DrVwLsuPImC--