Re: [PATCH 14/15] ide: rework the code for selecting the best DMAtransfer mode

[Sergei Shtylyov]

Hello, I wrote:
> > Bartlomiej Zolnierkiewicz wrote:

> > > [PATCH] ide: rework the code for selecting the best DMA transfer mode 

> > > Depends on the "ide: fix UDMA/MWDMA/SWDMA masks" patch.

> >   I'm now trying to rewrite hpt366.c to benefit more from these 
> > patches...
> > and alas, this very patch seems to be breaking filtering (at least) in 
> > this driver. :-]

> > > Index: b/drivers/ide/ide-dma.c
> > > ===================================================================
> > > --- a/drivers/ide/ide-dma.c
> > > +++ b/drivers/ide/ide-dma.c
> > > @@ -705,6 +705,80 @@ int ide_use_dma(ide_drive_t *drive)
> > >  
> > >  EXPORT_SYMBOL_GPL(ide_use_dma);
> > >  
> > > +static const u8 xfer_mode_bases[] = {
> > > +    XFER_UDMA_0,
> > > +    XFER_MW_DMA_0,
> > > +    XFER_SW_DMA_0,
> > > +};
> > > +
> > > +static unsigned int ide_get_mode_mask(ide_drive_t *drive, u8 base)
> > > +{
> > > +    struct hd_driveid *id = drive->id;
> > > +    ide_hwif_t *hwif = drive->hwif;
> > > +    unsigned int mask = 0;
> > > +
> > > +    switch(base) {
> > > +    case XFER_UDMA_0:
> > > +        if ((id->field_valid & 4) == 0)
> > > +            break;
> > > +
> > > +        mask = id->dma_ultra & hwif->ultra_mask;
> > > +
> > > +        if (hwif->udma_filter)
> > > +            mask &= hwif->udma_filter(drive);
> > > +
> > > +        if ((mask & 0x78) && (eighty_ninty_three(drive) == 0))
> > > +            mask &= 0x07;
>
>
> >   Note the subtle difference between the old and new behavior: the old 
> > driver code was applying UltraDMA filter *after*
> > the cable type limit, and the new code does it *before*.

>   Was there any particular reason to change that order?

  Ah, I see. Cable-reduced mask can't be passed back to driver's filter. This needs changing.

MBR, Sergei
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