From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wolfram Sang Subject: Re: [PATCH 2/5] i2c: sh_mobile: add DMA support Date: Thu, 11 Dec 2014 09:28:17 +0100 Message-ID: <20141211082817.GA2239@katana> References: <1415355104-2031-1-git-send-email-wsa@the-dreams.de> <20141211050226.GJ16827@intel.com> <20141211073727.GA1252@katana> <8247960.gkSH1BQ5uX@avalon> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="zYM0uCDKw75PZbzx" Return-path: Content-Disposition: inline In-Reply-To: <8247960.gkSH1BQ5uX@avalon> Sender: linux-sh-owner@vger.kernel.org To: Laurent Pinchart Cc: Vinod Koul , Magnus Damm , Geert Uytterhoeven , Linux I2C , Linux-sh list , Simon Horman , dmaengine@vger.kernel.org List-Id: linux-i2c@vger.kernel.org --zYM0uCDKw75PZbzx Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Dec 11, 2014 at 09:47:29AM +0200, Laurent Pinchart wrote: > On Thursday 11 December 2014 08:37:27 Wolfram Sang wrote: > > > I think this is a limitation of driver may not be for HW. The right m= odel > > > for dma_chan is to be viewed as SW channels and not the ones of HW (y= es > > > that is how most of the drivers use that, but we can improve upon) > > >=20 > > > If we rework the driver to view dma_chan as SW channels, then you can > > > accept multiple channel requests and accept based on if we are able l= ink > > > the channel to that peripheral or not. > >=20 > > In my understanding, the DMA driver does exactly that. >=20 > Actually it doesn't at the moment, I should implement that. OK, so I was misinterpreting the overcommitment. Thanks for the correction! > > However, it is not even loaded at the time the I2C driver wants a chann= el, > > so the dmaengine core defers the probe. That is the problem for optiona= l DMA > > channels: we can't know when deferring probe won't help anymore and don= 't > > know when it is time to fall back to PIO. >=20 > This is true regardless of the whether the driver exposes HW or SW channe= ls. Yup. --zYM0uCDKw75PZbzx Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBAgAGBQJUiVWgAAoJEBQN5MwUoCm2PA8QAInOOPLWsmLB2S0HtdYeLJod Xmri9s4PlZs+iMEjF8oY/5RMEba8Y9FQk2fBeoKDQOuY1lhutIwYT3jk5AibUKCw 0h88MNAUlxL61Ia/l1bZimfXYpIzWUGxizek4M2AXZnPOzVb2OyARimzeurxCtQx r3BATuQ30cXhXtoJxcvzI9vfdISVJtCAdn5JJilGxYimyd0nt4PETNMw3cAGyU2z xiAhliIxYId/YI4D0WQpyub7a1CbrnU1Sw9360hUROg36E8ice2ZASc6TAUn8mqT 4QGP4BZMlXuTcgLGsR/NwBnHhVG6PbJlVS9cMhW4yCot+CobT0ZbNPxw0ytJ8/QT +nn6qY8E2wiqdSsoHk9Mhwtzh8PqSh+EEz76TqKpt0ttYy+qNYmRoAJ5uwKxx0x+ B/oBILryCJTWn8Br/66KRSVUKbamRYaO40eMI6I6n+vejG+IuotXVmSLo9Vc4hHI +fvxynKLduzZBeQo8ROhovc0YEyQpd0UUrZE/qg+HRAoP/I9GLkK43x0l54+fGRh qnoPTNruMLItmjkx1doVjJoDouopKWoghmWjL7TGhpnZieYfGyyjZzyDbPWziXWX 4fWOopmCNMtSupL+fOgy6Gva/bQcFZmWBPg72WZ+JOibv8fT/EJc2UH7Cq8W1ef0 lHvO6I8nCOn52jDREHSw =EUr9 -----END PGP SIGNATURE----- --zYM0uCDKw75PZbzx--