From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753802Ab3GIMc7 (ORCPT ); Tue, 9 Jul 2013 08:32:59 -0400 Received: from comal.ext.ti.com ([198.47.26.152]:36130 "EHLO comal.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753617Ab3GIMc5 (ORCPT ); Tue, 9 Jul 2013 08:32:57 -0400 Message-ID: <51DC02EB.8070905@ti.com> Date: Tue, 9 Jul 2013 07:32:43 -0500 From: Nishanth Menon User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130623 Thunderbird/17.0.7 MIME-Version: 1.0 To: Mark Brown CC: Felipe Balbi , Sourav Poddar , , , , , Subject: Re: [PATCHv3 2/3] drivers: spi: Add qspi flash controller References: <1373290980-17883-1-git-send-email-sourav.poddar@ti.com> <1373290980-17883-3-git-send-email-sourav.poddar@ti.com> <20130708203330.GA28322@kahuna> <20130709065143.GC5552@arwen.pp.htv.fi> <20130709100525.GR27646@sirena.org.uk> In-Reply-To: <20130709100525.GR27646@sirena.org.uk> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/09/2013 05:05 AM, Mark Brown wrote: > On Tue, Jul 09, 2013 at 09:51:43AM +0300, Felipe Balbi wrote: > >>> Looks like a case to use regmap? >>> Dumb q: why cant we use regmap_spi? worst case, you should be able to > >> read regmap-spi and you'll see why it can't be used in this case. > >> regmap-spi is for SPI clients who want to read their register map >> through SPI commands. This is a driver for the SPI master which has its >> registers memory mapped. > > Indeed, regmap-spi would be a client of this driver. Though there is > regmap-mmio which may be helpful, on the other hand it's relatively > heavyweight and SPI can be a bit performance sensitive so perhaps it's > not awesome here. Russell did mention the idea of some helpers along a > similar style though, they may be a good idea but nobody wrote them yet. > Fair enough. I am starting to see at least a second driver (internally for DRA7 IRQ/DMA crossbar) doing the same handling for different bit sized registers. maybe now is the time for us to create a lighter version of mmio. mmio at least the last I looked uses spinlocks and is fairly fast. But, I agree, when the client of regmap uses locks to protect operations of their own, regmap might be a bit of an overhead. that said, replicating regmap logic in the driver looks a bit weird and might allow the basis for other drivers to do the same as well as some users of mmio would consider themselves performance sensitive :(. -- Regards, Nishanth Menon