Re: [PATCH][RFC] ServerWorks autodma behavior

[Ken Brownfield]

On Tue, Feb 26, 2002 at 09:52:57AM +0000, Alan Cox wrote:
| > I have a lot of ServerWorks OSB4 IDE hardware, which has the annoyingly
| > suboptimal behavior of corrupting filesystems when DMA is active.
| 
| With newer kernels you should get a panic because we spot the "I'm going
| to get 4 bytes stuck in the FIFO and DMA your inodes shifted 4 bytes down the
| disk behaviour" - at least in the cases I could study
| 
| What set up do you have ?

These machines are Tyan Thunder LE (S2510) non-SCSI boards with Seagate
drives.  Dual-P3.

| > Unfortunately, serverworks.c (in recent 2.4, at least) does not honor
| > the CONFIG_IDEDMA_AUTO config option -- it turns dma on only unless
| > "ide=nodma" is set on the kernel command line.
| 
| You actually really to just turn off UDMA from experience.

Yeah -- but I'd like to be able to enable it if I need the performance
on a more DMA-able motherboard.  Turning it off entirely would have
worked, of course.

| >  	if (hwif->dma_base) {
| > +#ifdef CONFIG_IDEDMA_AUTO
| >  		if (!noautodma)
| >  			hwif->autodma = 1;
| > +#endif
| 
| I would have expected this to be a fix in the core code to ignore
| hwif->autodma but I'll admit I've not looked to see if that is practical.

That may be -- I was sticking with the obvious, least-invasive, least
IDE-core-clued evaluation. :)  This is also the same treatment of
noautodma found in the VIA driver.  The autodma setting from ide-pci
does seem to be correct -- deleting the code segment produces the same
DMA end-results, in the end, for ServerWorks.

Thanks much,
-- 
Ken.
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