From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753407Ab1DUNpr (ORCPT ); Thu, 21 Apr 2011 09:45:47 -0400 Received: from mail-fx0-f46.google.com ([209.85.161.46]:40827 "EHLO mail-fx0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753309Ab1DUNpq (ORCPT ); Thu, 21 Apr 2011 09:45:46 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=eHMGybbJwMV4pyuLKIkAtBb5c9GJxPWezjFyLJC6NCsQ3Rk+KigMHslvt/cKH0Qiy4 4c6XuPwM+WPiZqX0zl71tLe0TxldiUmykVE740dO/Dk1JONusl/suWR5+3o7dLV0nMp0 gjnAIRjG0A1XLre7bz4zdh3aAZbSBAyDPoW7Q= Date: Thu, 21 Apr 2011 15:40:54 +0200 From: Tejun Heo To: Jian Peng Cc: Jeff Garzik , linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1] libata: ahci_start_engine compliant to AHCI spec Message-ID: <20110421134054.GE31724@htj.dyndns.org> References: <1303249499-11557-1-git-send-email-jipeng2005@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1303249499-11557-1-git-send-email-jipeng2005@gmail.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 19, 2011 at 02:44:59PM -0700, Jian Peng wrote: > At the end of section 10.1 of AHCI spec (rev 1.3), it states > > Software shall not set PxCMD.ST to 1 until it is determined that a > functoinal device is present on the port as determined by > PxTFD.STS.BSY=0, PxTFD.STS.DRQ=0 and PxSSTS.DET=3h > > Even though most AHCI host controller works without this additional > check, specific controller will fail without this. > > Signed-off-by: Jian Peng Acked-by: Tejun Heo But some nitpicks below. > + u8 status = readl(port_mmio + PORT_TFDATA) & 0xFF; It usually isn't customary to initialize variable with a statement which has side effect, especially hardware access. Please make the readl a separate statement. > + if (status & (ATA_BUSY | ATA_DRQ) || > + ahci_scr_read(&ap->link, SCR_STATUS, &tmp) || Also, ahci_scr_read() is known not to fail on host port in ahci and it's customary to skip error return in such cases in low level drivers. > + (tmp & 0x0f) != 0x03) > + return; And please add comment explaining what condition is being checked. It's much easier to read comment than digging through changelog and find out what the code is trying to achieve. Thanks. -- tejun