From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bartlomiej Zolnierkiewicz Subject: Re: cmd64x: irq 14: nobody cared - system is dreadfully slow Date: Tue, 23 Jun 2009 18:13:08 +0200 Message-ID: <200906231813.09570.bzolnier@gmail.com> References: <200906221938.27574.bzolnier@gmail.com> <20090623.031506.214747802.davem@davemloft.net> <200906231658.56489.elendil@planet.nl> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <200906231658.56489.elendil@planet.nl> Content-Disposition: inline Sender: sparclinux-owner@vger.kernel.org To: Frans Pop Cc: David Miller , sparclinux@vger.kernel.org, linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-ide@vger.kernel.org On Tuesday 23 June 2009 16:58:54 Frans Pop wrote: > On Tuesday 23 June 2009, you wrote: > > We might need to bisect this one. But Frans, just for the record > > could you simply test reverting just that hunk? Thanks! > > I'm way ahead of you :-) > > Instead of a bisect [1] I decided to first see if some printks in both .26 > and .31 would show anything useful. > > With 2.6.31 and code included below I get: > hda: ST34342A, ATA DISK drive > FJP: id_dma_bug 0x7: &4: 0x0-0x4 no error > hda: MWDMA2 mode selected > hdc: Maxtor 6E040L0, ATA DISK drive > hdd: CD-ROM 56X/AKH, ATAPI CD/DVD-ROM drive > hdc: host max PIO5 wanted PIO255(auto-tune) selected PIO4 > FJP: ID_FIELD_VALID: 0x7 (true) > FJP: id_dma_bug 0x7: &4: 0x0-0x4 no error > hdc: MWDMA2 mode selected > hdd: host max PIO5 wanted PIO255(auto-tune) selected PIO4 > FJP: ID_FIELD_VALID: 0x2 (true) > FJP: id_dma_bug 0x2: &2: 0x1-0x1 bad modes <------------- > hdd: bad DMA info in identify block > > Note that this included a complete revert of 8d64fcd9 (with minor conflict > resolved). > > Here's the same output with 2.6.26.3 with equivalent debug statements: > hda: ST34342A, ATA DISK drive > FJP: id_dma_bug 0x7: &4: 0x0-0x0 no error > hda: MWDMA2 mode selected > hdc: Maxtor 6E040L0, ATA DISK drive > hdd: CD-ROM 56X/AKH, ATAPI CD/DVD-ROM drive > FJP: id_dma_bug 0x7: &4: 0x0-0x0 no error > hdc: MWDMA2 mode selected > FJP: id_dma_bug 0x2: &2: 0x0-0x0 no error <------------- > hdd: MWDMA2 mode selected > > So it seems to me that in 2.6.26 something was broken in the way these ID > fields were handled, at least in this check. This is now fixed (possibly Great debugging work, thanks! > by the changes around 5b90e990..48fb2688) and *that* causes the > regression. Note that the hard disks are also affected. I see it now -- in commit c419993 ("ide-iops: only clear DMA words on setting DMA mode") we fixed a bug in ide_config_drive_speed().. [ It was a real bug resulting in incorrect data being passed to the user-space through HDIO_GET_IDENTITY ioctl ('hdparm -i'). ]