From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758380AbbICSlg (ORCPT ); Thu, 3 Sep 2015 14:41:36 -0400 Received: from mezzanine.sirena.org.uk ([106.187.55.193]:50262 "EHLO mezzanine.sirena.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757098AbbICSle (ORCPT ); Thu, 3 Sep 2015 14:41:34 -0400 Date: Thu, 3 Sep 2015 18:45:02 +0100 From: Mark Brown To: Shawn Lin Cc: Vinod Koul , Heiko Stuebner , Jaroslav Kysela , Takashi Iwai , Doug Anderson , Olof Johansson , Sonny Rao , Addy Ke , dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org, alsa-devel@alsa-project.org, linux-spi@vger.kernel.org, Olof Johansson Message-ID: <20150903174502.GI5313@sirena.org.uk> References: <1441101381-1329-1-git-send-email-shawn.lin@rock-chips.com> <1441101524-1700-1-git-send-email-shawn.lin@rock-chips.com> <20150903125429.GA12027@sirena.org.uk> <55E84E17.2090409@rock-chips.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="mQQrPwpUFXnyQ/Ik" Content-Disposition: inline In-Reply-To: <55E84E17.2090409@rock-chips.com> X-Cookie: Short people get rained on last. User-Agent: Mutt/1.5.23 (2014-03-12) X-SA-Exim-Connect-IP: 94.175.94.161 X-SA-Exim-Mail-From: broonie@sirena.org.uk Subject: Re: [PATCH v3 8/9] spi: rockchip: modify DMA max burst to 1 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 --mQQrPwpUFXnyQ/Ik Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Sep 03, 2015 at 09:41:43PM +0800, Shawn Lin wrote: > On 2015/9/3 20:54, Mark Brown wrote: > >If this is a quirk of the DMA controller why is it being fixed with a > >property specific to the SPI controller? Can't the DMA controller just > >override the burst size? > Cool...that's a good question. Actually DMA controller can't do that since > block peripheral controller(e.g sd/emmc, they always access data by > block-512Bytes.) can't meet the case. So It's hard for dma controller know > who is the caller, and what should be done. You could take a guess based on request size, but that's going to be a bit error prone I imagine. > The only thing dma controller can do is avoid to execute DMAFLUSHP on its > own. But how about peripheral controller trigger non-multiple access? So > that's what I mentioned on covery letter that we should do "broken things" > for both dma controller and some peripherals. The other thing it could do is provide the information out via some internal Linux API which the drivers could query instead of directly having a DT property in each client driver. That way at least the DT only needs the quirk in one place even if the clients need to handle it individually. --mQQrPwpUFXnyQ/Ik Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQEcBAEBCAAGBQJV6IcdAAoJECTWi3JdVIfQpHMH/3uUXqmELNJ+DjZAtIuTAML4 F3Ma1D3F1hxiZzEmlGNB9mI/VBZP4EhQ+NzHrc8Wn/pqIvuBumGqdrYj0MdnKhYn FJ3olHfbAZtJ3a1vBtriGvPhRAbWUEqAYUuCoue4ZUfJ6vF81KttN6yjzO929209 iuUkQiqGZnLySLL1yqHbZb61ruABOSmOrgJR3qFU/72dJB7xDY61JIrzZxwGEsaB fMrU4I4KsJPG3dl02upMA8G0X1LWnGe5AcKVdOxCGFj6swP1WyTtQyLLLqx1Ks31 8J6MlWZLHg7/b13dgfh+jsg+j2wYIODjmTlu8UhyZru0EBVTAbffjX8CPCR2/Xk= =w/6n -----END PGP SIGNATURE----- --mQQrPwpUFXnyQ/Ik--