Messages in this thread | | | Date | Thu, 20 Nov 2008 14:40:32 +0900 | Subject | Re: ISP1760 driver crashes | From | FUJITA Tomonori <> |
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On Wed, 19 Nov 2008 18:21:25 +0100 Jens Axboe <jens.axboe@oracle.com> wrote:
> On Wed, Nov 19 2008, Alan Stern wrote: > > On Wed, 19 Nov 2008, Jens Axboe wrote: > > > > > > --- usb-2.6.orig/drivers/scsi/scsi_lib.c > > > > +++ usb-2.6/drivers/scsi/scsi_lib.c > > > > @@ -1684,7 +1684,7 @@ static void scsi_request_fn(struct reque > > > > u64 scsi_calculate_bounce_limit(struct Scsi_Host *shost) > > > > { > > > > struct device *host_dev; > > > > - u64 bounce_limit = 0xffffffff; > > > > + u64 bounce_limit = BLK_BOUNCE_HIGH; > > > > > > > > if (shost->unchecked_isa_dma) > > > > return BLK_BOUNCE_ISA; > > > > > > > > > > The best solution is probably to either provide a "doesn't do highmem" > > > in the scsi host template, or provide an appropriate DMA mask for the > > > pci device to indicate it through that setting instead. > > > > The DMA mask is currently set to NULL. Is that not appropriate for a > > device that can't do DMA? If not, then what would be appropriate? > > It's changing behaviour. There's no current rule that says if you don't > have a dma mask set, we only do PIO (even if such a rule DOES make > sense). Additionally, you don't HAVE to bounce for PIO. As I wrote > earlier, it's perfectly feasible to use bio kmap'ings to do the > transfer. > > > Also, is the patch above not correct? > > It'll certainly work in the sense that if you don't have a dma_mask set, > you only get lowmem pages. Whether the new behaviour is something we > want, not sure. Check with James what he thinks, it's his domain.
We have been used 4GB for long time if dma_mask is zero (I guess we use 4GB as kinda the default dma address limit at several places). The majority of drivers (such as pci) sets properly dev->dma_mask so the patch might not change anything but suddenly changing the long-standing rule in an odd way (use BLK_BOUNCE_HIGH if dma_mask is zero) doesn't sound a good idea to me.
Why not calling blk_queue_bounce_limit() in the slave_configure hook? I think that it's the common way for SCSI LLDs with odd bounce limit.
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