linux-kernel - Re: [PATCH 14/15] ide: rework the code for selecting the best DMA transfer mode

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Date:	Fri, 20 Apr 2007 19:03:39 +0400
From:	Sergei Shtylyov <sshtylyov@...mvista.com>
To:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
CC:	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 14/15] ide: rework the code for selecting the best DMA
 transfer mode

Hello, I 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. :-]

  Ignore me, I've seemingly misundertood the code. :-<

>>> 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);
>>> +            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. :-)

>>> @@ -576,10 +564,10 @@ static u8 hpt3xx_ratefilter(ide_drive_t 
>>>              /* fall thru */
>>>          case 0x00:
>>>          default:
>>> -            speed = min_t(u8, speed, XFER_MW_DMA_2);
>>> +            mask = 0x00;
>>>              break;

>   Well, that case 0x00 should never actually happen.

   Yeah, that's true, 'case 0x00' (and even 'default') labels could have been removed.

MBR, Sergei

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