Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758682AbYBOVqi (ORCPT ); Fri, 15 Feb 2008 16:46:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757794AbYBOVqZ (ORCPT ); Fri, 15 Feb 2008 16:46:25 -0500 Received: from gate.crashing.org ([63.228.1.57]:35438 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757755AbYBOVqY (ORCPT ); Fri, 15 Feb 2008 16:46:24 -0500 Subject: Re: [PATCH] libata: Add MMIO support to pata_sil680 From: Benjamin Herrenschmidt Reply-To: benh@kernel.crashing.org To: Alan Cox Cc: Guennadi Liakhovetski , Tim Ellis , linux-kernel@vger.kernel.org, jeff@garzik.org In-Reply-To: <20080215155332.2b89c429@core> References: <32334D99-DB01-4645-97DC-88D2E7BA2BE5@ngndg.com> <1202850129.7410.22.camel@pasglop> <20080215155332.2b89c429@core> Content-Type: text/plain Date: Sat, 16 Feb 2008 08:45:56 +1100 Message-Id: <1203111956.22915.24.camel@pasglop> Mime-Version: 1.0 X-Mailer: Evolution 2.12.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2955 Lines: 80 On Fri, 2008-02-15 at 15:53 +0000, Alan Cox wrote: > > > That's strange though. Somebody with knowledge of that HW (or specs) who > > > can spot something ? Could it be an issue with timing ? > > > > > > I don't have HW access to this machine. If somebody could send one to me > > > I could do more investigation. > > > > Ben, would an ssh access to such a machine and to a terminal server > > suffice? > > It says clearly in the code where to start. See the FIXME notes in both > libata-sff and libata-core about MMIO. Neither the DMA transfer start or > the probe SRST sequence are correct with MMIO posting and this hasn't > been fixed as I pointed out was needed when I originally NAKked the > change. > > Without those being fixed (especially SRST) on any device with heavy PCI > posting of mmio your controller *wont work*. The dbdma start is mostly harmless (things don't get posted for -that- long), though I suppose it's worth fixing. Would reading back dmactl do in that case or do you foresee any kind of side effect ? (Maybe only doing it for MMIO ?) As for SRST, I'm not totally confident how safe it is to read back there while doing the reset sequence, so I'm tempted to really only do it for MMIO and use altstat rather than ctl/stat (the later tends to have side effects which we don't want here). What do you think ? The main problem from here is that I don't know whether we are using MMIO or PIO from libata-core. Maybe I can add a host flag indicate that such flushing is needed ? In the meantime, Guennadi, can you check if that patch helps for you (to see if that is indeed the problem): diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c index 004dae4..1451a52 100644 --- a/drivers/ata/libata-core.c +++ b/drivers/ata/libata-core.c @@ -3461,10 +3461,13 @@ static int ata_bus_softreset(struct ata_port *ap, unsigned int devmask, /* software reset. causes dev0 to be selected */ iowrite8(ap->ctl, ioaddr->ctl_addr); + ioread16(ioaddr->nsect_addr); udelay(20); /* FIXME: flush */ iowrite8(ap->ctl | ATA_SRST, ioaddr->ctl_addr); + ioread16(ioaddr->nsect_addr); udelay(20); /* FIXME: flush */ iowrite8(ap->ctl, ioaddr->ctl_addr); + ioread16(ioaddr->nsect_addr); /* wait a while before checking status */ ata_wait_after_reset(ap, deadline); diff --git a/drivers/ata/libata-sff.c b/drivers/ata/libata-sff.c index 60cd4b1..81d5828 100644 --- a/drivers/ata/libata-sff.c +++ b/drivers/ata/libata-sff.c @@ -273,6 +273,7 @@ void ata_bmdma_start(struct ata_queued_cmd *qc) * FIXME: The posting of this write means I/O starts are * unneccessarily delayed for MMIO */ + ioread8(ap->ioaddr.bmdma_addr + ATA_DMA_CMD); } /** Cheers, Ben. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/