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SubjectRe: [PATCH 14/15] ide: rework the code for selecting the best DMA transfer mode
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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