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SubjectRe: 2.5.7 pre-UDMA PIIX bug
Mikael Pettersson wrote:
> Vojtech's version of drivers/ide/piix.c which went into 2.5.7
> oopses with a divide-by-zero exception when initialising older
> pre-UDMA chips, like in the following 430HX chipset:
>
> 00:00.0 Host bridge: Intel Corporation 430HX - 82439HX TXC [Triton II] (rev 03)
> 00:07.0 ISA bridge: Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton II] (rev 01)
> 00:07.1 IDE interface: Intel Corporation 82371SB PIIX3 IDE [Natoma/Triton II]
> (PCI IDs 8086:1250, 8086:7000, and 8086:7010, respectively)
>
> The error occurs in piix.c:piix_set_drive() line 334, shown below.
> The 82371SB has PIIX_UDMA_NONE in the piix_ide_chips[] array,
> so piix_config->flags & PIIX_UDMA is zero, which makes "umul" zero,
> which causes the divide-by-zero on line 334.
>
> 317 static int piix_set_drive(ide_drive_t *drive, unsigned char speed)
> 318 {
> 319 ide_drive_t *peer = HWIF(drive)->drives + (~drive->dn & 1);
> 320 struct ata_timing t, p;
> 321 int err, T, UT, umul;
> 322
> 323 if (speed != XFER_PIO_SLOW && speed != drive->current_speed)
> 324 if ((err = ide_config_drive_speed(drive, speed)))
> 325 return err;
> 326
> 327 umul = min((speed > XFER_UDMA_4) ? 4 : ((speed > XFER_UDMA_2) ? 2 : 1),
> 328 piix_config->flags & PIIX_UDMA);
> 329
> 330 if (piix_config->flags & PIIX_VICTORY)
> 331 umul = 2;
> 332
> 333 T = 1000000000 / piix_clock;
> 334 UT = T / umul;

I think that it should be just sufficient to add the
following test just in front of the offending calculartion.

if (umul == 0)
++umul;

Vojtech is this right?

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