On Sat, Oct 30 1999, Arnd Bergmann wrote:
> Hi!
>
> I always get a 'Kernel panic: Buffer at physical address > 16Mb
> used for aha1542' when accessing my cd-writer as a cd rom drive
> in the latest 2.3 kernels.
> Roel Teuwen (Roel.Teuwen@advalvas.be) has reporeted the same
> problem some weeks ago.
>
> The problem is that the current sr driver uses transfer buffers
> on the stack instead of scsi_malloc()'ed ones like the 2.2.x
> driver. This will not work with ISA scsi adaptors using DMA.
> I wrote a small patch that implements extra buffering in the
> same way the sd drivers uses them, which works perfectly for me.
Yes, that is exactly the problem. This is something I missed
when I cleaned it up.
> The patch is attached to this mail and I put it up on
> http://www.et.fh-osnabrueck.de/~std7652/scsi-dmabuf.patch as
> well.
>
> I'm not sure whether I got the spin locks right so this should
> be checked before it get included in a main kernel.
You don't need the spin locks in sr_packet - in fact, there seems
to be quite a spin lock frenzy going on in the various SCSI
devices (sr* and sd*). And I don't like the concept of calling
panic() either, when we can just fail the request gracefully.
> {
> DECLARE_MUTEX_LOCKED(sem);
> SCpnt->request.sem = &sem;
> +
> + /* use ISA DMA buffer if necessary */
> + SCpnt->request.buffer=buffer;
> + if (buffer && SCpnt->host->unchecked_isa_dma
> + && (virt_to_phys(buffer) + buflength - 1 > ISA_DMA_THRESHOLD)) {
> + spin_lock_irqsave(&io_request_lock, flags);
> + bounce_buffer=(char *)(scsi_malloc((buflength + 511) & ~511));
> + if (!bounce_buffer)
> + panic("SCSI DMA pool exhausted.");
> + memcpy(bounce_buffer,(char *)buffer,buflength);
> + spin_unlock_irqrestore(&io_request_lock, flags);
> + buffer=bounce_buffer;
> + }
> +
This is inside the retry loop?
I reworked the patch a bit (and also cleaned up the scsi_do_cmd()
in sr_ioctl.c) - does this look ok?
-- * Jens Axboe <axboe@image.dk> * Linux CD-ROM Maintainer * http://www.kernel.dk--tKW2IUtsqtDRztdT Content-Type: text/plain; charset=us-ascii Content-Disposition: attachment; filename="scsi-dma.diff"
diff -ur scsi/sr.c /usr/src/linux/drivers/scsi/sr.c --- scsi/sr.c Sun Oct 24 14:39:33 1999 +++ /usr/src/linux/drivers/scsi/sr.c Sat Oct 30 19:57:27 1999 @@ -1030,6 +1030,8 @@ { Scsi_Cmnd *SCpnt; Scsi_Device *device = scsi_CDs[MINOR(cdi->dev)].device; + unsigned char *buffer = cgc->buffer; + int buflen; int stat; /* get the device */ @@ -1037,6 +1039,17 @@ if (SCpnt == NULL) return -ENODEV; /* this just doesn't seem right /axboe */ + /* use buffer for ISA DMA */ + buflen = (cgc->buflen + 511) & ~511; + if (cgc->buffer && SCpnt->host->unchecked_isa_dma && + (virt_to_phys(cgc->buffer) + cgc->buflen - 1 > ISA_DMA_THRESHOLD)) { + if ((buffer = scsi_malloc(buflen)) == NULL) { + printk("sr: SCSI DMA pool exhausted."); + return -ENOMEM; + } + memcpy(buffer, cgc->buffer, cgc->buflen); + } + /* set the LUN */ cgc->cmd[1] |= device->lun << 5; @@ -1044,8 +1057,8 @@ SCpnt->request.rq_dev = cdi->dev; /* scsi_do_cmd sets the command length */ SCpnt->cmd_len = 0; - - scsi_wait_cmd (SCpnt, (void *)cgc->cmd, (void *)cgc->buffer, cgc->buflen, + + scsi_wait_cmd (SCpnt, (void *)cgc->cmd, (void *)buffer, cgc->buflen, sr_init_done, SR_TIMEOUT, MAX_RETRIES); stat = SCpnt->result; @@ -1054,6 +1067,12 @@ SCpnt->request.rq_dev = MKDEV(0, 0); scsi_release_command(SCpnt); SCpnt = NULL; + + /* write DMA buffer back if used */ + if (buffer && (buffer != cgc->buffer)) { + memcpy(cgc->buffer, buffer, cgc->buflen); + scsi_free(buffer, buflen); + } return stat; } diff -ur scsi/sr_ioctl.c /usr/src/linux/drivers/scsi/sr_ioctl.c --- scsi/sr_ioctl.c Mon Oct 11 12:06:45 1999 +++ /usr/src/linux/drivers/scsi/sr_ioctl.c Sat Oct 30 19:54:26 1999 @@ -36,6 +36,12 @@ req = &SCpnt->request; req->rq_status = RQ_SCSI_DONE; /* Busy, but indicate request done */ + + if (SCpnt->buffer && req->buffer && SCpnt->buffer != req->buffer) { + memcpy(req->buffer, SCpnt->buffer, SCpnt->bufflen); + scsi_free(SCpnt->buffer, (SCpnt->bufflen + 511) & ~511); + SCpnt->buffer = req->buffer; + } if (req->sem != NULL) { up(req->sem); @@ -52,27 +58,33 @@ Scsi_Device * SDev; int result, err = 0, retries = 0; unsigned long flags; + char * bounce_buffer; spin_lock_irqsave(&io_request_lock, flags); SDev = scsi_CDs[target].device; SCpnt = scsi_allocate_device(NULL, scsi_CDs[target].device, 1); spin_unlock_irqrestore(&io_request_lock, flags); + /* use ISA DMA buffer if necessary */ + SCpnt->request.buffer=buffer; + if (buffer && SCpnt->host->unchecked_isa_dma && + (virt_to_phys(buffer) + buflength - 1 > ISA_DMA_THRESHOLD)) { + bounce_buffer = (char *)scsi_malloc((buflength + 511) & ~511); + if (bounce_buffer == NULL) { + printk("SCSI DMA pool exhausted."); + return -ENOMEM; + } + memcpy(bounce_buffer, (char *)buffer, buflength); + buffer = bounce_buffer; + } + retry: if( !scsi_block_when_processing_errors(SDev) ) return -ENODEV; - { - DECLARE_MUTEX_LOCKED(sem); - SCpnt->request.sem = &sem; - spin_lock_irqsave(&io_request_lock, flags); - scsi_do_cmd(SCpnt, - (void *) sr_cmd, buffer, buflength, sr_ioctl_done, - IOCTL_TIMEOUT, IOCTL_RETRIES); - spin_unlock_irqrestore(&io_request_lock, flags); - down(&sem); - SCpnt->request.sem = NULL; - } - + + scsi_wait_cmd(SCpnt, (void *)sr_cmd, (void *)buffer, buflength, + sr_ioctl_done, IOCTL_TIMEOUT, IOCTL_RETRIES); + result = SCpnt->result; /* Minimal error checking. Ignore cases we know about, and report the rest. */
--tKW2IUtsqtDRztdT--
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