Re: [parisc-linux] Re: Why toggle_bounce only for disks?

[Jens Axboe <axboe@suse.de>]

On Fri, Aug 19 2005, James Bottomley wrote:
> On Fri, 2005-08-19 at 12:21 +0200, Jens Axboe wrote:
> > Because not bouncing is a performance optimization and I only did the
> > work on ide-cd to allow it. Your patch breaks ide-cd on highmem i386
> > machines, so it's not acceptable.
> > 
> > Tells us more about this crash instead, I'm pretty sure you are working
> > around another issue (your io-mmu code, is it hardware or software?)
> > somehwere with this patch.
> 
> OK, so the particular fix is wrong; but the logic in ide_toggle_bounce()
> is also incorrec.  Our problem is not that we don't want to bounce
> highmem in ide-cd, it's that this is a parisc system with an IOMMU and
> doesn't have any highmem to begin with.
> 
> we need ide_toggle_bounce to return BLK_BOUNCE_ANY always if
> PCI_DMA_BUS_IS_PHYS is not set.
> 
> James
> 
> diff --git a/drivers/ide/ide-lib.c b/drivers/ide/ide-lib.c
> --- a/drivers/ide/ide-lib.c
> +++ b/drivers/ide/ide-lib.c
> @@ -410,10 +410,10 @@ void ide_toggle_bounce(ide_drive_t *driv
>  {
>  	u64 addr = BLK_BOUNCE_HIGH;	/* dma64_addr_t */
>  
> -	if (on && drive->media == ide_disk) {
> -		if (!PCI_DMA_BUS_IS_PHYS)
> -			addr = BLK_BOUNCE_ANY;
> -		else if (HWIF(drive)->pci_dev)
> +	if (!PCI_DMA_BUS_IS_PHYS)
> +		addr = BLK_BOUNCE_ANY;
> +	else if (on && drive->media == ide_disk) {
> +		if (HWIF(drive)->pci_dev)
>  			addr = HWIF(drive)->pci_dev->dma_mask;
>  	}

That looks more correct, indeed. It's really too convoluted for drivers,
the defines/setup could do with a little work-over.

-- 
Jens Axboe