Messages in this thread | | | Date | Wed, 19 Nov 2008 16:39:23 +0100 | From | Jens Axboe <> | Subject | Re: ISP1760 driver crashes |
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On Wed, Nov 19 2008, Alan Stern wrote: > On Wed, 19 Nov 2008, Jens Axboe wrote: > > > On Wed, Nov 19 2008, Alan Stern wrote: > > > On Wed, 19 Nov 2008, Sebastian Andrzej Siewior wrote: > > > > > > > Hommel, Thomas (GE EntSol, Intelligent Platforms) wrote: > > > > > > > > > I indeed have HIGHMEM enabled in my configuration. > > > > > I recompiled the kernel without HIGHMEM and it works. I don't think that > > > > > this a satisfying solution for a board with up to 2GB of RAM and > > > > > considerable amount of VMALLOC space, but at least this works. > > > > > If you have any more ideas how to circumvent this, please let me know. > > > > Sure, this is not a sollution but atleast now I know what happens: > > > > - The kernel allocates memory for transfer > > > > - the memory is highmem and not in kernel so the buffer is NULL > > > > - we don't have a dma-mask and therefore the dma address is 0 > > > > - boom > > > > > > > > The sollution would be probably to prevent the usb-storage core to > > > > allocate memory from HIGHMEM. > > > > > > usb-storage doesn't allocate the memory. The memory is allocated by > > > the block layer or the filesystem. > > > > > > > Now I don't if there is a flag for something > > > > like that and I am not using that. On the other hand this may be broken > > > > for a long time and you are the first one which has that much memory with > > > > no DMA-capable USB controller. > > > > > > Jens, is there any way to tell the kernel that a device uses PIO and > > > therefore its buffers shouldn't be allocated in high memory? For > > > example, shouldn't a NULL dma_mask do this? > > > > Sure, just use blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH), then you are > > certain that you will always have a virtual mapping for the IO you > > receive. > > > > Or you can use the bio kmap/kunmap helpers to get such a mapping > > temporarily if you wish. But if your pio condition is permanent, you may > > as well just use bouncing. > > Thank you. > > Thomas, the blk_queue_bounce_limit() routine is called in > drivers/scsi/scsi_lib.c:__scsi_alloc_queue(). The value it passes is > computed by scsi_calculate_bounce_limit(), and in that routine > host_dev->dma_mask should be NULL (since isp1760-hcd sets the mask to > NULL). Therefore the bounce limit should be 0xffffffff. > > Now maybe this value isn't correct. You can try the patch below to see > if it helps. If it doesn't, add a printk in __scsi_alloc_queue() to > see what bounce limit value is getting used. > > Alan Stern > > > > Index: usb-2.6/drivers/scsi/scsi_lib.c > =================================================================== > --- 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.
-- Jens Axboe
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