From mboxrd@z Thu Jan 1 00:00:00 1970 From: Igor Plyatov Subject: Re: [PATCH] ata: pata_at91.c bugfix for high master clock Date: Sat, 11 Dec 2010 22:43:31 +0300 Message-ID: <1292096611.27634.20.camel@homepc> References: <1292011430-20835-1-git-send-email-plyatov@gmail.com> <4D0385D1.9080209@ru.mvista.com> <1292081113.1580.21.camel@homepc> <4D039930.4050905@ru.mvista.com> Reply-To: plyatov@gmail.com Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-ey0-f171.google.com ([209.85.215.171]:64736 "EHLO mail-ey0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751329Ab0LKTng (ORCPT ); Sat, 11 Dec 2010 14:43:36 -0500 In-Reply-To: <4D039930.4050905@ru.mvista.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Sergei Shtylyov Cc: jgarzik@pobox.com, linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org, geomatsi@gmail.com Dear Sergei, > > I do not test this driver, but I think it have the same problem, because > > it have the same algorithm for timings calculation. > > I quickly looked thru both drivers and the algorithm seemed different. :-) I don't think so... > > If you will see "cycle" value greater then 63, then problem exists. > > I thought the problem was with active pulse width, not total cycle time... The problem was - the same "cycle" variable used to set up NRD_CYCLE (max value = 127) and NCS_RD_PULSE (max value = 63). Where NRD_CYCLE, NCS_RD_PULSE names from datasheet for AT91SAM9. If NCS_RD_PULSE > 63, then overflow occur and pulse is much longer then required. For the 132 MHz, driver use NCS_RD_PULSE = 80 at device detection moment on my board. Calculated cycle in at91_ide is the same as for pata_at91 driver. > > Generally, I does not see any reasons to use at91_ide, because ATA > > drivers subsystem going to replace IDE drivers. > > There may be reasons -- like larger thruput in PIO mode (you have to check > this though -- but generally libata seems very slow in PIO). Anyway, it > doesn't mean that the bugs in IDE drivers should be ignored, and the > replacemtn will not happen anytime soon (not all IDE drivers are ported to > libata yet). I will send next patch where this driver corrected and tested. Best regards! -- Igor Plyatov