From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: PMP device port link speed issues Date: Thu, 25 Oct 2007 06:25:51 -0400 Message-ID: <47206F2F.4020206@garzik.org> References: <2A6F278C5B66C4459AF4013E77A40CD301003114@zin33exm20.fsl.freescale.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from srv5.dvmed.net ([207.36.208.214]:45181 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754264AbXJYKZx (ORCPT ); Thu, 25 Oct 2007 06:25:53 -0400 In-Reply-To: <2A6F278C5B66C4459AF4013E77A40CD301003114@zin33exm20.fsl.freescale.net> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Kalra Ashish-B00888 Cc: IDE/ATA development list Kalra Ashish-B00888 wrote: > While testing the "sata_fsl" driver with a Sil3726 based PMP, we had a > specific configuration where the host port to PMP link speed was > 1.5Gbps, while the PMP has configured it's device port(s) link speed to > 3Gbps. This configuration causes NCQ hangs on certain Seagate drives, > probably because of the link speed difference between host and PMP > device & PMP device ports and drives. > > Does it makes sense to limit the PMP device port link speeds to the host > port link speed ? > > I believe currently sata_pmp_attach() is calling sata_link_init_spd() > for each PMP device port and thus causing PMP device port link speeds > being configured independent of host port link speed. Probably the PMP > device port links should be limited to the host link speed. Interesting question. I'm sure Tejun will chime in, but I'm wondering if there is any real use -- even theoretical -- for running downstream links faster than the host<->PMP link? Jeff