From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753536AbeDJOFS (ORCPT ); Tue, 10 Apr 2018 10:05:18 -0400 Received: from mail.bootlin.com ([62.4.15.54]:50094 "EHLO mail.bootlin.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753118AbeDJOFQ (ORCPT ); Tue, 10 Apr 2018 10:05:16 -0400 Date: Tue, 10 Apr 2018 16:05:04 +0200 From: Maxime Ripard To: Sergey Suloev Cc: Chen-Yu Tsai , Mark Brown , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-spi@vger.kernel.org Subject: Re: [PATCH v3 3/6] spi: sun6i: restrict transfer length in PIO-mode Message-ID: <20180410140504.i7kszskwxuoygt5s@flea> References: <20180405131735.GB12349@sirena.org.uk> <8159c3a5-af74-9f13-aedb-7ecc708bdff6@orpaltech.com> <20180406073441.xesojvzc3deljhoy@flea> <204e97cb-2f39-00f0-fd4e-3aa9a51f7cac@orpaltech.com> <20180409092730.2moyhl5aaktjwbyn@flea> <94a394bd-89bf-9334-c500-4cbadf4c1044@orpaltech.com> <20180409105001.GC11532@sirena.org.uk> <67c2006b-17f2-2459-e3c9-e91e3c694d8c@orpaltech.com> <20180409113603.2iexkqvyeqmysp5e@flea> <0e2fefa5-b6e7-5e42-cf6e-8fc921f972dd@orpaltech.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="b4q666t6sgvco2sh" Content-Disposition: inline In-Reply-To: <0e2fefa5-b6e7-5e42-cf6e-8fc921f972dd@orpaltech.com> User-Agent: NeoMutt/20180323 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --b4q666t6sgvco2sh Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Apr 09, 2018 at 02:59:57PM +0300, Sergey Suloev wrote: > > > But as soon as sun4i SPI driver=A0 is correctly declaring > > > max_transfer_size then "smart" clients will work well by limiting a > > > single transfer size to FIFO depth. I tested it with real hardware, > > > again. > > This is really not my point. What would prevent you from doing > > multiple transfers in that case, and filling the FIFO entirely, > > waiting for it to be done, then resuming until you have sent the right > > number of bytes? > > Because it makes no sense IMHO. I can't see any single point in allowing > long PIO transfers. Can you find at least one ? I'm probably going to state the obvious here, but to allow long transfers? > I think we should reuse as much SPI core code as possible. The SPI > core can handle an SPI message with multiple transfers, all we need > is to have max_transfer_size =3D FIFO depth and restrict it in > transfer_one(). There's not a single call to the max_transfer_size hook in the SPI core in 4.16, so that seems a bit too optimistic. Maxime --=20 Maxime Ripard, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com --b4q666t6sgvco2sh Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEE0VqZU19dR2zEVaqr0rTAlCFNr3QFAlrMxI8ACgkQ0rTAlCFN r3SbrQ//TFFVHDCIE9JtIeazfWuz9k4LebEYXhTIiMcUGLUWvJojjRVlmrR14rZA R9JmR0ytUic7r/v4lBBP/P/JSlY/ljcR8XGNfxYe0GnhOGYYB9ety/xu8jHfJ92W d6zsgUuhOLkjuP3u7Ox9w7d5Qv0itLkic7n8DMjnwVsqLPt4gQLYp4s6QVZ86cKA 1viXDzJwrM+e2y1/Mhi8/9dtkoyylyTSzU7ILl9jWQPM7ARDgNJlxq4bSl6mhmkz CBIFZBoXm3RlnHk7THdCypTG8eA3ouJD/Z8X6DxmNOcLIz/7tA/+eGX9IqbnBgwn nMwMB0jFAU/h8yABmpCzduvDdMO1nJY+EQl93/dLR+YiXAqbZIfZj+eZaTb/A3Bv /kskvfzYcywAecX30RISteepIQiHWpjDObZ0fhxAym/MiwNGJFKFtKtM6R0bqk88 mHaxo6nRjr8+0RCjw9+coQY1sHmf3pFkLvK60GDmO7eGENlMmIBN1UCowXDI/Uem YoIiEDFnpnyDz6j3yjhOJYbfKa8xM971Z6RCu2kLcVJ8iVYaA1/bfQHE/WX4EKd9 eEqiDAsXzbekbDsISIoxohzYP+NSN+NRbFcZypzQGICVF+F8S68yx0R4v3ls6lgH WzxFLGS/norkO1WEsB88+KMocXz1KyIUHFPTDMynO7ErJUAdblk= =bs5n -----END PGP SIGNATURE----- --b4q666t6sgvco2sh--