From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Brown Subject: Re: [PATCH 1/3] Documentation:spi:fsl-dspi:add DSPI dma transfer support Date: Thu, 27 Feb 2014 00:38:22 +0900 Message-ID: <20140226153822.GC2394@sirena.org.uk> References: <1393311258-14380-1-git-send-email-b44548@freescale.com> <20140225090830.GO28555@e106331-lin.cambridge.arm.com> <20140226141947.GE23892@S2101-09.ap.freescale.net> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="PuGuTyElPB9bOcsM" Cc: Mark Rutland , Chao Fu , "linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" To: Shawn Guo Return-path: Content-Disposition: inline In-Reply-To: <20140226141947.GE23892-rvtDTF3kK1ictlrPMvKcciBecyulp+rMXqFh9Ls21Oc@public.gmane.org> Sender: linux-spi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: --PuGuTyElPB9bOcsM Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, Feb 26, 2014 at 10:19:49PM +0800, Shawn Guo wrote: > On Tue, Feb 25, 2014 at 09:08:30AM +0000, Mark Rutland wrote: > > > +- use-dma: the bool decide if use dma method in DSPI transfering. > > Why can the OS not decide this based on the presence of dmas which it > > can use? > Yes, OS/driver should decide to use DMA or not, but it shouldn't be > based on the presence of 'dmas' property. The DMA is a hardware > resource just like IRQ. It should be just there in client device's node > as long as the SoC design assigns the channel to the device. The device > driver should make the decision when DMA should be used, e.g. big amount > data transfer, and when PIO should be used, e.g. small data. Right, that's very common - but that decision is usually taken on a per transfer basis so a DT property would seem odd, especially just a simple boolean. --PuGuTyElPB9bOcsM Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iQIcBAEBAgAGBQJTDgpmAAoJELSic+t+oim9UwgP/iKN+UxCcQesTmx57ClFgynd Skz32s76kUAa8EOGHyDmZ1UdEad6AytxpYv0YKIlJPQBO+CI7eWGXJ2yHGM+FLxb QIG6ZFVd/u6q47NV4m3kxNsyX9EXyBCWqoCOGK3uffV6QdWPGXiCcV3CnK/Fpptx qbZxQE1uwYBAVBzO7ravumvxE+uUZOVhz+IoMm0OMUCyCtwm9n/1RHXqdgqHprYf 1QysQCnNQP5g5tZ2l+lh+MRvLVRhFAOykeTHcapdpPkv1A3isitz7fEiVPVaaqnP tGYDvxJfmBvwq7KH3OgAIhsJH1Pv1ax4rPFPZI0ufo5LfUwrgev0/bKeivVKAXfd P4m7UCId/9TVPFubPhXaQ0Fltfiy9OmfYj4G5oZG4Iw8YQSSdQr1cU+CtC1wlreY IM/kAGj08ZoczJxJlLHNTAK1VUv/alVR8P6nVvmyY793idTmo5FwBhOSe+wVRdVK aOT/7nbUMsuCjzyNK/nwpp5Z+yYGTD4QYtBCqTbVeGylTDpxMaCJfb29nlity88P 17CydR4JDZn9/vQ+rAiYlADoShhPYheTw4aepXDsnaBH+50Y9OALg59DzvmWeJ/g Oi+PocFsC1gVmuJ0nZ5l8nkbJKy8BJay+jeEQMPN6DbTgcxMEu3dzfjgW1QoN1d8 STHVYk3DV3ICXcT4vVlK =Asic -----END PGP SIGNATURE----- --PuGuTyElPB9bOcsM-- -- To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html From mboxrd@z Thu Jan 1 00:00:00 1970 From: broonie@kernel.org (Mark Brown) Date: Thu, 27 Feb 2014 00:38:22 +0900 Subject: [PATCH 1/3] Documentation:spi:fsl-dspi:add DSPI dma transfer support In-Reply-To: <20140226141947.GE23892@S2101-09.ap.freescale.net> References: <1393311258-14380-1-git-send-email-b44548@freescale.com> <20140225090830.GO28555@e106331-lin.cambridge.arm.com> <20140226141947.GE23892@S2101-09.ap.freescale.net> Message-ID: <20140226153822.GC2394@sirena.org.uk> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Feb 26, 2014 at 10:19:49PM +0800, Shawn Guo wrote: > On Tue, Feb 25, 2014 at 09:08:30AM +0000, Mark Rutland wrote: > > > +- use-dma: the bool decide if use dma method in DSPI transfering. > > Why can the OS not decide this based on the presence of dmas which it > > can use? > Yes, OS/driver should decide to use DMA or not, but it shouldn't be > based on the presence of 'dmas' property. The DMA is a hardware > resource just like IRQ. It should be just there in client device's node > as long as the SoC design assigns the channel to the device. The device > driver should make the decision when DMA should be used, e.g. big amount > data transfer, and when PIO should be used, e.g. small data. Right, that's very common - but that decision is usually taken on a per transfer basis so a DT property would seem odd, especially just a simple boolean. -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 836 bytes Desc: Digital signature URL: