Hello. Anton Vorontsov wrote:
IDE interrupt handler relies on the fact that, if necessary, hardirqs will re-trigger on ISR exit. The assumption is valid for level sensitive interrupts.
It's valid for both edge and level triggered interrupts.
But some hardware (namely ULi M5228 in the ULi M1575 "Super South Brige") behaves in a strange way: it asserts interrupts as edge sensitive. And because preemptable IRQ handler disables PIC's interrupt, PIC will likely miss it.
Unmasking an IRQ should re-enable an edge detector in a PIC (or that detector should even be independent from mask). So, unless an IRQ signal is a short pulse (which shouldn't be the case for IDE) it shouldn't be missed.
This patch fixes following issue: ALI15X3: IDE controller (0x10b9:0x5229 rev 0xc8) at PCI slot 0001:03:1f.0 ALI15X3: 100% native mode on irq 18 ide0: BM-DMA at 0x1120-0x1127, BIOS settings: hda:PIO, hdb:PIO ide1: BM-DMA at 0x1128-0x112f, BIOS settings: hdc:PIO, hdd:PIO hda: Optiarc DVD RW AD-7190A, ATAPI CD/DVD-ROM drive hda: UDMA/66 mode selected ide0 at 0x1100-0x1107,0x110a on irq 18 ide-cd: cmd 0x5a timed out hda: lost interrupt hda: ATAPI 12X DVD-ROM DVD-R-RAM CD-R/RW drive, 2048kB Cache Uniform CD-ROM driver Revision: 3.20 ide-cd: cmd 0x3 timed out hda: lost interrupt ide-cd: cmd 0x3 timed out hda: lost interrupt ... It would be great to re-configure the ULi bridge or ULi IDE controller to behave sanely, but no one knows how or if this is possible at all (no available specifications). So.. to workaround the issue IDE interrupt handler should re-check for any pending IRQs. This isn't bulletproof solution, but it works and this is the best one we can do
I remembered a pssible issue with such code: it's possible that BSY bit will be cleared before INTRQ assertion (this is a race not spotted for a long time by the ATA standards -- and an observed behavior, at least of some ATAPI drives), thus a status register read won't clear the "interrupt pending" condition within drive.
MBR, Sergei -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
