Re: [RFC] Patch to fix cdrom being confused on using kdump

[Jens Axboe]

On Fri, Apr 07 2006, Rachita Kothiyal wrote:
> Hi Jens
> 
> As we had discussed earlier, I had seen the cdrom drive appearing
> confused on using kdump on certain x86_64 systems. During the booting 
> up of the second kernel, the following message would keep flooding
> the console, and the booting would not proceed any further.
> 
> hda: cdrom_pc_intr: The drive appears confused (ireason = 0x01)
> 
> In this patch, whenever we are hitting a confused state in the interrupt
> handler with the DRQ set, we clear the DSC bit of the status register and 
> return 'ide_stopped' from the interrupt handler. 
> 
> Please provide your comments and feedback.
> 
> Thanks
> Rachita
> 
> 
> Signed-off-by: Rachita Kothiyal <rachita@xxxxxxxxxx>
> ---
> 
>  drivers/ide/ide-cd.c |    5 +++++
>  1 files changed, 5 insertions(+)
> 
> diff -puN drivers/ide/ide-cd.c~cdrom-confused-clrinterrupt drivers/ide/ide-cd.c
> --- linux-2.6.16-mm2/drivers/ide/ide-cd.c~cdrom-confused-clrinterrupt	2006-03-29 11:23:18.000000000 +0530
> +++ linux-2.6.16-mm2-rachita/drivers/ide/ide-cd.c	2006-04-07 19:05:48.962710872 +0530
> @@ -1450,6 +1450,11 @@ static ide_startstop_t cdrom_pc_intr (id
>  			rq->sense_len += thislen;
>  	} else {
>  confused:
> +		if (( stat & DRQ_STAT) == DRQ_STAT) {

if (stat & DRQ_STAT)

checking for DRQ_STAT again doesn't make sense, how can it ever be
anything but DRQ_STAT if DRQ_STAT is set?

> +			/* DRQ is set. Interrupt not welcome now. Ignore */
> +			HWIF(drive)->OUTB((stat & 0xEF), IDE_STATUS_REG);
> +			return ide_stopped;

And this looks very wrong, you can't write to the status register. Well
you can, but then it's the command register! Writing stat & 0xef to the
command register is an odd thing to do. I think you just want to clear
the DRQ bit, which should be fine after it was read initially. How about


        if (stat & DRQ_STAT)
                return ide_stopped;

Can you test that?

-- 
Jens Axboe

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