From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161529AbcE3PEE (ORCPT ); Mon, 30 May 2016 11:04:04 -0400 Received: from mezzanine.sirena.org.uk ([106.187.55.193]:54972 "EHLO mezzanine.sirena.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161301AbcE3PEC (ORCPT ); Mon, 30 May 2016 11:04:02 -0400 Date: Mon, 30 May 2016 16:03:43 +0100 From: Mark Brown To: Geert Uytterhoeven Cc: Michal Suchanek , linux-sunxi , Maxime Ripard , Chen-Yu Tsai , linux-spi , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" Message-ID: <20160530150343.GL29837@sirena.org.uk> References: <20160530112610.GJ29837@sirena.org.uk> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="Qgd2S+2VS1hsWwXW" Content-Disposition: inline In-Reply-To: X-Cookie: Happy feast of the pig! User-Agent: Mutt/1.6.0 (2016-04-01) X-SA-Exim-Connect-IP: 2a01:348:6:8808:fab::3 X-SA-Exim-Mail-From: broonie@sirena.org.uk Subject: Re: [PATCH 5/5] RFC spi: sun4i: add DMA support X-SA-Exim-Version: 4.2.1 (built Mon, 26 Dec 2011 16:24:06 +0000) X-SA-Exim-Scanned: Yes (on mezzanine.sirena.org.uk) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --Qgd2S+2VS1hsWwXW Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Mon, May 30, 2016 at 02:11:51PM +0200, Geert Uytterhoeven wrote: > On Mon, May 30, 2016 at 1:26 PM, Mark Brown wrote: > > On Thu, May 26, 2016 at 07:25:25PM -0000, Michal Suchanek wrote: > >> - fallback to previous behaviour when DMA initialization fails > >> > >> + this has the problem that when the driver happens to load before the dma > >> driver it will not use dma - can be addressed with a module parameter > > No, you should pay attention to the error you are getting and let probe > > deferral happen if that's the error you get. > Unfortunately DMA is an optional feature. > There's no way to distinguish between -EPROBE_DEFER due to the SPI master > driver being probed before the DMA engine driver, and -EPROBE_DEFER due to > support for the DMA engine not having been compiled in. I really don't think it's worth caring too much about cases where the DMA driver hasn't been compiled in, it's not like SPI is the only thing that's going to be using it. I really think it's better to defer the problem - not getting DMA (or worse, only getting DMA on some boots) is not great and if people are optimising on that level my feeling is that they're probably going to be OK with customizing DT to match. Ideally we would have something a bit nicer than deferred probe but right now this seems the more helpful option. --Qgd2S+2VS1hsWwXW Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQEcBAEBCAAGBQJXTFZOAAoJECTWi3JdVIfQF2MH/jGER4xhRrRVnmypbt1jD3Ea 8R6NMBnbnk90mepjdqFuivd1c8x0nTiwl4tSuC3PxER+23kiSUQkaZhZOrpYQOug nzDdEqV3JOqNIbFFgaTEh9MyxCRooxw2jxFWXP/Ge0uKccqkmtjt0oMm4nDWbPrE +14ck33AFP/sMOT99RmTaj9BvXZbzFYjopOWlA54ITac77pPKLHjOhoL7F1bs0tX ykmNb9t3o/lhZbW2IsT243HQOYn4RBaZOrSnEumwZ4Xlnhx2Yzm5Wi4t2Y0jY7WR ddiU9zuTlLkrMmCeDTI+ISG6kCEm7ihRPAjVsePPln6lAExDoYYYfd6XiNq2/2M= =5O9F -----END PGP SIGNATURE----- --Qgd2S+2VS1hsWwXW--