On Friday 16 February 2007 16:34, Sergei Shtylyov wrote:
> Hello.
>
> Bartlomiej Zolnierkiewicz 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).
> >>
> >>>> That was expected behavior.
> >>
> >>>>>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
> >>
> >>>> The driver never supported UltraDMA on this revision, as indicated by
> >>>> that
> >>>>message.
> >>
> >>>>>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.
> >>
> >>>> The intent of the patch was exactly to *remove* broken DMA support
> >>>> until
> >>>>it's fixed (which requires more work). It only worked by chance --
> >>>>because
> >>>>MWDMA2 timings are the same as of PIO4. Have patience please.
> >>
> >>>It only worked by chance but it _worked_, especially for the usual case,
> >>>MWDMA2/PIO4 == all newer drives (despite writing 0x10 reserved bit of
> >>>BMIDESR0/1 for the master devices). I think I'll remove the patch for now.
>
> >> Then I will protest. :-) This was *not* fixable all at once. And
> >> removing
> >>it just because some users happen to have the *known buggy* (and so reduced
> >>to
> >>MWDMA only) chips is a wrong thing to do.
>
> PCI0643 would also suffer, to be precise.
>
> > OK, I'm not removing it but it needs (rather urgent) fixing.
>
> >>>To fix SWDMA/MWDMA properly isn't it enough to just call cmd64x_tune_pio()
> >>>from cmd64x_tune_chipset() to tune the corresponding PIO mode?
>
> >> No, that wouldn't be a clean fix, just a kind of workaround -- it will
> >>also change the address setup times (which is not quite desirable). I can
>
> > I see, how about:
>
> > * splitting off setup timing programming from program_drive_counts()
> > into separate function (setup timing is programmed into separate register)
>
> Yes, it's on my todo list. But consider the amount of cleanup work I had
> to do (and have in drafts still) for 2.6.21-rc1 -- if it really gets there
> :-). And also, consider that currently I have a plenty of internal bugs to
> fix besides IDE (and they're not as obvious as IDE ones).
>
> > * pushing ide_get_best_pio_mode() call to higher layers
> > [ cmd64x_tune_driver() only, it is not needed in cmd64x_tune_chipset() ]
>
> Ehm, is it really there? I thought I left it in cmd64x_tune_pio() where
> it's on its right place...
Yes, it is still there - I meant pushing it up to avoid programming setup
time when programming timings for DMA modes.
> > * calling new function setting setup timing from cmd64x_tune_drive()
> > and cmd64x_tune_chipset() (here for PIO modes only)
>
> I ceratainly don't want to put this into cmd64x_tune_chipset() -- this
> should be handled in cmd64x_tune_pio() still.
>
> > * calling cmd64x_tune_pio() fro SWDMA/MWDMA
>
> Erm? Putting time-to-cycle converion into program_drive_counts() sound
> like a better plan.
agreed
> > Would the above assembly into the proper SWDMA/MWDMA fix?
>
> Not all items did make sense to me, sorry. :-)
>
> >>compose such quickie in five minutes though.
>
> > I can wait some time for the proper fix but if you see that
> > it won't happen soon (week?) please send me this workaround.
>
> I think it will happen in a week.
OK.
Thanks,
Bart
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