As des' example shows us, DMA overruns could happen in a situation
where they will never succeed. Add a stop-gap measure that will at least eventually timeout the operation instead of retrying it indefinately. MFC after: 1 month
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joerg
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8e095496f1
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@ -97,6 +97,13 @@
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#define FD_FAILED -1
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#define FD_NOT_VALID -2
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#define FDC_ERRMAX 100 /* do not log more */
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/*
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* Stop retrying after this many DMA overruns. Since each retry takes
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* one revolution, with 300 rpm., 25 retries take approximately 10
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* seconds which the read attempt will block in case the DMA overrun
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* is persistent.
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*/
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#define FDC_DMAOV_MAX 25
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#define NUMTYPES 17
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#define NUMDENS (NUMTYPES - 7)
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@ -1451,6 +1458,18 @@ Fdopen(dev_t dev, int flags, int mode, struct proc *p)
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}
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fd->ft = fd_types + type - 1;
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fd->flags |= FD_OPEN;
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/*
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* Clearing the DMA overrun counter at open time is a bit messy.
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* Since we're only managing one counter per controller, opening
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* the second drive could mess it up. Anyway, if the DMA overrun
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* condition is really persistent, it will eventually time out
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* still. OTOH, clearing it here will ensure we'll at least start
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* trying again after a previous (maybe even long ago) failure.
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* Also, this is merely a stop-gap measure only that should not
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* happen during normal operation, so we can tolerate it to be a
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* bit sloppy about this.
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*/
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fdc->dma_overruns = 0;
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return 0;
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}
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@ -2033,16 +2052,23 @@ fdstate(fdc_p fdc)
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if ((fdc->status[0] & NE7_ST0_IC) == NE7_ST0_IC_AT
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&& fdc->status[1] & NE7_ST1_OR) {
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/*
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* DMA overrun. Someone hogged the bus
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* and didn't release it in time for the
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* next FDC transfer.
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* Just restart it, don't increment retry
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* count. (vak)
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*/
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fdc->state = SEEKCOMPLETE;
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return (1);
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* DMA overrun. Someone hogged the bus and
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* didn't release it in time for the next
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* FDC transfer.
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*
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* We normally restart this without bumping
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* the retry counter. However, in case
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* something is seriously messed up (like
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* broken hardware), we rather limit the
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* number of retries so the IO operation
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* doesn't block indefinately.
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*/
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if (fdc->dma_overruns++ < FDC_DMAOV_MAX) {
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fdc->state = SEEKCOMPLETE;
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return (1);
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} /* else fall through */
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}
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else if((fdc->status[0] & NE7_ST0_IC) == NE7_ST0_IC_IV
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if((fdc->status[0] & NE7_ST0_IC) == NE7_ST0_IC_IV
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&& fdc->retry < 6)
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fdc->retry = 6; /* force a reset */
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else if((fdc->status[0] & NE7_ST0_IC) == NE7_ST0_IC_AT
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@ -2060,6 +2086,8 @@ fdstate(fdc_p fdc)
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idp->sec = fdc->status[5];
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idp->secshift = fdc->status[6];
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}
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/* Operation successful, retry DMA overruns again next time. */
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fdc->dma_overruns = 0;
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fd->skip += fdblk;
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if (!rdsectid && !format && fd->skip < bp->bio_bcount) {
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/* set up next transfer */
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46
sys/isa/fd.c
46
sys/isa/fd.c
@ -97,6 +97,13 @@
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#define FD_FAILED -1
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#define FD_NOT_VALID -2
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#define FDC_ERRMAX 100 /* do not log more */
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/*
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* Stop retrying after this many DMA overruns. Since each retry takes
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* one revolution, with 300 rpm., 25 retries take approximately 10
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* seconds which the read attempt will block in case the DMA overrun
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* is persistent.
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*/
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#define FDC_DMAOV_MAX 25
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#define NUMTYPES 17
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#define NUMDENS (NUMTYPES - 7)
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@ -1451,6 +1458,18 @@ Fdopen(dev_t dev, int flags, int mode, struct proc *p)
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}
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fd->ft = fd_types + type - 1;
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fd->flags |= FD_OPEN;
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/*
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* Clearing the DMA overrun counter at open time is a bit messy.
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* Since we're only managing one counter per controller, opening
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* the second drive could mess it up. Anyway, if the DMA overrun
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* condition is really persistent, it will eventually time out
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* still. OTOH, clearing it here will ensure we'll at least start
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* trying again after a previous (maybe even long ago) failure.
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* Also, this is merely a stop-gap measure only that should not
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* happen during normal operation, so we can tolerate it to be a
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* bit sloppy about this.
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*/
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fdc->dma_overruns = 0;
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return 0;
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}
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@ -2033,16 +2052,23 @@ fdstate(fdc_p fdc)
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if ((fdc->status[0] & NE7_ST0_IC) == NE7_ST0_IC_AT
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&& fdc->status[1] & NE7_ST1_OR) {
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/*
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* DMA overrun. Someone hogged the bus
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* and didn't release it in time for the
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* next FDC transfer.
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* Just restart it, don't increment retry
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* count. (vak)
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*/
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fdc->state = SEEKCOMPLETE;
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return (1);
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* DMA overrun. Someone hogged the bus and
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* didn't release it in time for the next
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* FDC transfer.
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*
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* We normally restart this without bumping
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* the retry counter. However, in case
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* something is seriously messed up (like
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* broken hardware), we rather limit the
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* number of retries so the IO operation
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* doesn't block indefinately.
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*/
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if (fdc->dma_overruns++ < FDC_DMAOV_MAX) {
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fdc->state = SEEKCOMPLETE;
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return (1);
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} /* else fall through */
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}
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else if((fdc->status[0] & NE7_ST0_IC) == NE7_ST0_IC_IV
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if((fdc->status[0] & NE7_ST0_IC) == NE7_ST0_IC_IV
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&& fdc->retry < 6)
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fdc->retry = 6; /* force a reset */
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else if((fdc->status[0] & NE7_ST0_IC) == NE7_ST0_IC_AT
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@ -2060,6 +2086,8 @@ fdstate(fdc_p fdc)
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idp->sec = fdc->status[5];
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idp->secshift = fdc->status[6];
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}
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/* Operation successful, retry DMA overruns again next time. */
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fdc->dma_overruns = 0;
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fd->skip += fdblk;
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if (!rdsectid && !format && fd->skip < bp->bio_bcount) {
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/* set up next transfer */
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@ -80,6 +80,7 @@ struct fdc_data
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u_int status[7]; /* copy of the registers */
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enum fdc_type fdct; /* chip version of FDC */
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int fdc_errs; /* number of logged errors */
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int dma_overruns; /* number of DMA overruns */
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struct bio_queue_head head;
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struct bio *bp; /* active buffer */
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struct resource *res_ioport, *res_ctl, *res_irq, *res_drq;
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