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

[Sergei Shtylyov]

Hello, I wrote:

> > > > Index: b/drivers/ide/pci/hpt366.c
> > > > ===================================================================
> > > > --- a/drivers/ide/pci/hpt366.c
> > > > +++ b/drivers/ide/pci/hpt366.c
> > > > @@ -513,43 +513,31 @@ static int check_in_drive_list(ide_drive
> > > >      return 0;
> > > >  }
> > > >  
> > > > -static u8 hpt3xx_ratemask(ide_drive_t *drive)
> > > > -{
> > > > -    struct hpt_info *info    = pci_get_drvdata(HWIF(drive)->pci_dev);
> > > > -    u8 mode            = info->max_mode;
> > > > -
> > > > -    if (!eighty_ninty_three(drive) && mode)
> > > > -        mode = min(mode, (u8)1);
> > > > -    return mode;
> > > > -}
> > > > -
> > > >  /*
> > > >   *    Note for the future; the SATA hpt37x we must set
> > > >   *    either PIO or UDMA modes 0,4,5
> > > >   */
> > > > - -static u8 hpt3xx_ratefilter(ide_drive_t *drive, u8 speed)
> > > > +
> > > > +static u8 hpt3xx_udma_filter(ide_drive_t *drive)
> > > >  {
> > > >      struct hpt_info *info    = pci_get_drvdata(HWIF(drive)->pci_dev);
> > > >      u8 chip_type        = info->chip_type;
> > > > -    u8 mode            = hpt3xx_ratemask(drive);
> > > > -
> > > > -    if (drive->media != ide_disk)
> > > > -        return min(speed, (u8)XFER_PIO_4);
> > > > +    u8 mode            = info->max_mode;
> > > > +    u8 mask;
> > > >  
> > > >      switch (mode) {
> > > >          case 0x04:
> > > > -            speed = min_t(u8, speed, XFER_UDMA_6);
> > > > +            mask = 0x7f;
> > > >              break;
> > > >          case 0x03:
> > > > -            speed = min_t(u8, speed, XFER_UDMA_5);
> > > > +            mask = 0x3f;
> > > >              if (chip_type >= HPT374)
> > > >                  break;
> > > >              if (!check_in_drive_list(drive, bad_ata100_5))
> > > >                  goto check_bad_ata33;
> > > >              /* fall thru */
> > > >          case 0x02:
> > > > -            speed = min_t(u8, speed, XFER_UDMA_4);
> > > > +            mask = 0x1f;
> > > >  
> > > >              /*
> > > >               * CHECK ME, Does this need to be changed to HPT374 ??
> > > > @@ -560,13 +548,13 @@ static u8 hpt3xx_ratefilter(ide_drive_t 
> > > >                  !check_in_drive_list(drive, bad_ata66_4))
> > > >                  goto check_bad_ata33;
> > > >  
> > > > -            speed = min_t(u8, speed, XFER_UDMA_3);

 Hm, found a buglet in my former filtering rewrite -- the condition in the preceding if stmt should be a reverse one, and speed limitation to XFER_UDMA_3 should have been left under it.  With the current code, XFER_UDMA_2 limitation wouldn't have been applied if the same drive is not in both 'bad_ata66_4' and 'bad_ata66_3' lists -- this, however, actually is not the case since WDC AC310200R drive is in both these lists (maybe I wrote it this way because of this fact :-).

> > > > +            mask = 0x0f;
> > > >              if (HPT366_ALLOW_ATA66_3 &&
> > > >                  !check_in_drive_list(drive, bad_ata66_3))
> > > >                  goto check_bad_ata33;
> > > >              /* fall thru */
> > > >          case 0x01:
> > > > -            speed = min_t(u8, speed, XFER_UDMA_2);
> > > > +            mask = 0x07;
> > > >  
> > > >          check_bad_ata33:
> > > >              if (chip_type >= HPT370A)

> > >   This case 0x01 will *never* be hit for HPT370 chip with the new 
> > > code, therefore the filter won't get applied.

> >   Oh, and for HPT36x chips used with 40c cable too (unless they're 
> > artificaially reduced to UltraDMA/33 by the driver #define's).

>   It will still get applied since the code always resorts to looking up 
> the 'bad_ata33' list for HPT36x/370.
> I've got a bit muddled in my own code -- not sure if it got much clearer 
> after I'd untangled hpt3xx_ratemask() / hpt3xx_ratefilter() puzzle. :-)

 Yeah, I'm definitely having trouble understanding my own code after some months have passed... :-/

MBR, Sergei

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