Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752513AbdCBMaH convert rfc822-to-8bit (ORCPT ); Thu, 2 Mar 2017 07:30:07 -0500 Received: from mail.thorsis.com ([213.211.200.15]:53601 "EHLO mail.thorsis.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752318AbdCBMaF (ORCPT ); Thu, 2 Mar 2017 07:30:05 -0500 From: Alexander Dahl To: linux-arm-kernel@lists.infradead.org Cc: Boris Brezillon , Nicolas Ferre , Alexandre Belloni , Lee Jones , Samuel Ortiz , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/7] memory: atmel-ebi: Simplify SMC config code Date: Thu, 02 Mar 2017 13:02:16 +0100 Message-ID: <16727676.CMj9rWYKWZ@ada> Organization: Thorsis Technologies GmbH User-Agent: KMail/4.14.1 (Linux/3.16.0-4-amd64; KDE/4.14.2; x86_64; ; ) In-Reply-To: <1487609701-10300-3-git-send-email-boris.brezillon@free-electrons.com> References: <1487609701-10300-1-git-send-email-boris.brezillon@free-electrons.com> <1487609701-10300-3-git-send-email-boris.brezillon@free-electrons.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1526 Lines: 51 Hei hei, With #define ATMEL_SMC_MODE_TDF(x) (((x) - 1) << 16) from include/linux/mfd/syscon/atmel-smc.h you added this: > + ret = of_property_read_u32(np, "atmel,smc-tdf-ns", &val); > + if (!ret) { > + required = true; > + ncycles = DIV_ROUND_UP(val, clk_period_ns); > + if (ncycles > ATMEL_SMC_MODE_TDF_MAX) { > + ret = -EINVAL; > + goto out; > + } […] > + smcconf->mode |= ATMEL_SMC_MODE_TDF(ncycles); > + } This was the same algorithm at some other location in atmel-ebi.c before: #define AT91_SMC_TDF_(x) ((((x) - 1) << 16) & AT91_SMC_TDF) val = DIV_ROUND_UP(timings->tdf_ns, clk_rate); if (val > AT91_SMC_TDF_MAX) val = AT91_SMC_TDF_MAX; regmap_fields_write(fields->mode, conf->cs, config->mode | AT91_SMC_TDF_(val)); The hardware manual (AT91SAM9G20) says values from 0 to 15 (4bit, 0x0 to 0xF) are possible and I guess the goal is to set it to a value corresponding to the value in ns from the dts or to 15 if it's greater (or -EINVAL in the new version). However how can one set it to zero? Put in zero to the div you get zero for ncycles or val and that goes as x into (((x) - 1) << 16) which results in 0xF ending up as TDF_CYCLES in the mode register, right? I can of course set a slightly greater value, which ends up in a calculated register value of zero, but that seems more a hack to me and is not obvious if I just look at the DTS. If I'm right this might be topic of another bugfix patch, or should it be done right in a v2 of this one? Greets Alex