From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH v2] drivers: ata: wake port before DMA stop for ALPM Date: Mon, 25 Jan 2016 15:23:03 -0500 Message-ID: <20160125202303.GK3628@mtj.duckdns.org> References: <1452547346-31735-1-git-send-email-dpetigara@broadcom.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-pf0-f194.google.com ([209.85.192.194]:33992 "EHLO mail-pf0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932246AbcAYUXG (ORCPT ); Mon, 25 Jan 2016 15:23:06 -0500 Content-Disposition: inline In-Reply-To: <1452547346-31735-1-git-send-email-dpetigara@broadcom.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Danesh Petigara Cc: linux-ide@vger.kernel.org, f.fainelli@gmail.com, computersforpeace@gmail.com, gregory.0xf0@gmail.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, bcm-kernel-feedback-list@broadcom.com On Mon, Jan 11, 2016 at 01:22:26PM -0800, Danesh Petigara wrote: > The AHCI driver code stops and starts port DMA engines at will > without considering the power state of the particular port. The > AHCI specification isn't very clear on how to handle this scenario, > leaving implementation open to interpretation. > > Broadcom's STB SATA host controller is unable to handle port DMA > controller restarts when the port in question is in low power mode. > When a port enters partial or slumber mode, its PHY is powered down. > When a controller restart is requested, the controller's internal > state machine expects the PHY to be brought back up by software which > never happens in this case, resulting in failures. > > To avoid this situation, logic is added to manually wake up the port > just before its DMA engine is stopped, if the port happens to be in > a low power state. HBA initiated power management ensures that the port > eventually returns to its configured low power state, when the link is > idle (as per the conditions listed in the spec). A new host flag is also > added to ensure this logic is only exercised for hosts with the above > limitation. > > Signed-off-by: Danesh Petigara > Reviewed-by: Markus Mayer Applied to libata/for-4.5-fixes w/ some formatting changes. Thanks. -- tejun