On Thu, 8 Feb 2007 09:58:45 +0100 (MET), Mikael Pettersson wrote:
>On Thu, 8 Feb 2007 00:00:32 +0300, Sergei Shtylyov wrote:
>>Remove the bogus code pretending to set SW/MW DMA timings -- I wonder whether
>>its author really thought that he could achieve that wrtiting to BMIDE status
>>registers? Stop fiddling with the DMA capable bits in the speedproc() -- they
>>do not enable DMA, and are properly dealt with by the dma_host_{on,off} methods;
>>also, get rid of the duplicate reads/writes of UDIDETCRx registers, and do some
>>coding style and whitespace changes while at it...
>>
>>Unfortunately, fixing the SW/MW DMA support would requre a major driver rewrite
>>along with some more fixing, so I'm putting it off...
>>
>>Warning: this has been compile-tested only.
>
>Worked fine on my SPARC Ultra5.
Correction: I was only looking for absence of errors when testing
this patch. However, later I found that this patch (version 1.42
of cmd64x.c) disabled DMA on my CMD646, dropping performance to
1/4th (from about 13MB/s to about 3.5MB/s according to hdparm -Tt).
Here's the relevant kernel messages from before this patch:
ide: Assuming 33MHz system bus speed for PIO modes; override with idebus=xx
CMD646: IDE controller at PCI slot 0000:01:03.0
CMD646: chipset revision 3
CMD646: chipset revision 0x03, MultiWord DMA Force Limited
CMD646: 100% native mode on irq 14
ide0: BM-DMA at 0x1fe02c00020-0x1fe02c00027, BIOS settings: hda:pio, hdb:pio
ide1: BM-DMA at 0x1fe02c00028-0x1fe02c0002f, BIOS settings: hdc:pio, hdd:pio
Probing IDE interface ide0...
hda: ST320420A, ATA DISK drive
ide0 at 0x1fe02c00000-0x1fe02c00007,0x1fe02c0000a on irq 14
Probing IDE interface ide1...
hdc: CRD-8483B, ATAPI CD/DVD-ROM drive
ide1 at 0x1fe02c00010-0x1fe02c00017,0x1fe02c0001a on irq 14 (shared with ide0)
hda: max request size: 128KiB
hda: 39851760 sectors (20404 MB) w/2048KiB Cache, CHS=39535/16/63, (U)DMA
hda: cache flushes not supported
hda: hda1 hda2 hda3 hda4 hda5
With the patch the kernel messages are the same, except for the
3rd last line which becomes:
hda: 39851760 sectors (20404 MB) w/2048KiB Cache, CHS=39535/16/63
i.e., the (U)DMA indicator is gone.
Please revert this until the regression is fixed.
/Mikael
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