On Fri, Jun 14, 2019 at 03:27:36PM +1000, Finn Thain wrote:
> Hi Ming,
>
> On Fri, 14 Jun 2019, Ming Lei wrote:
>
> > Use the scatterlist iterators and remove direct indexing of the
> > scatterlist array.
> >
> > This way allows us to pre-allocate one small scatterlist, which can be
> > chained with one runtime allocated scatterlist if the pre-allocated one
> > isn't enough for the whole request.
> >
> > Signed-off-by: Ming Lei <ming....@redhat.com>
> > ---
> > drivers/scsi/aha152x.c | 29 +++++++++++++++++++----------
> > 1 file changed, 19 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/scsi/aha152x.c b/drivers/scsi/aha152x.c
> > index 97872838b983..bc9d12aa7880 100644
> > --- a/drivers/scsi/aha152x.c
> > +++ b/drivers/scsi/aha152x.c
> > @@ -2033,7 +2033,7 @@ static void datai_run(struct Scsi_Host *shpnt)
> > CURRENT_SC->SCp.buffers_residual > 0) {
> > /* advance to next buffer */
> > CURRENT_SC->SCp.buffers_residual--;
> > - CURRENT_SC->SCp.buffer++;
> > + CURRENT_SC->SCp.buffer =
> > sg_next(CURRENT_SC->SCp.buffer);
> > CURRENT_SC->SCp.ptr =
> > SG_ADDRESS(CURRENT_SC->SCp.buffer);
> > CURRENT_SC->SCp.this_residual =
> > CURRENT_SC->SCp.buffer->length;
> > }
> > @@ -2139,7 +2139,7 @@ static void datao_run(struct Scsi_Host *shpnt)
> > if(CURRENT_SC->SCp.this_residual==0 &&
> > CURRENT_SC->SCp.buffers_residual>0) {
> > /* advance to next buffer */
> > CURRENT_SC->SCp.buffers_residual--;
> > - CURRENT_SC->SCp.buffer++;
> > + CURRENT_SC->SCp.buffer =
> > sg_next(CURRENT_SC->SCp.buffer);
> > CURRENT_SC->SCp.ptr =
> > SG_ADDRESS(CURRENT_SC->SCp.buffer);
> > CURRENT_SC->SCp.this_residual =
> > CURRENT_SC->SCp.buffer->length;
> > }
> > @@ -2160,20 +2160,29 @@ static void datao_end(struct Scsi_Host *shpnt)
> > if(TESTLO(DMASTAT, DFIFOEMP)) {
> > int data_count = (DATA_LEN - scsi_get_resid(CURRENT_SC)) -
> > GETSTCNT();
>
> data_count appears to be the number of bytes remaining in the FIFO. (I
> have to infer that much from the surrounding code. I don't have
> documentation for this controller.)
Yeah, it should be so, that is the data which need to transfer again.
>
> Some comments would be nice.
>
> > + struct scatterlist *sg = scsi_sglist(CURRENT_SC);
> > + int left, i = 0;
> >
> > CMD_INC_RESID(CURRENT_SC, data_count);
> >
>
> Apparently the aim is to increase the residual by the number of bytes that
> will never leave the FIFO. Above we can see that increase performed by
> scsi_set_resid() and now the same has to be done to the SCp struct.
Agree.
>
> > data_count -= CURRENT_SC->SCp.ptr -
> > SG_ADDRESS(CURRENT_SC->SCp.buffer);
>
> Here, data_count effectively has SCp.this_residual subtracted from it.
>
> > - while(data_count>0) {
> > - CURRENT_SC->SCp.buffer--;
> > - CURRENT_SC->SCp.buffers_residual++;
> > - data_count -= CURRENT_SC->SCp.buffer->length;
> > - }
>
> So far, so good.
>
> > - CURRENT_SC->SCp.ptr = SG_ADDRESS(CURRENT_SC->SCp.buffer) -
> > - data_count;
> > - CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length +
> > - data_count;
>
> This is like saying ptr = buffer + residual, which is bogus. This must be
> an old bug, but we never hit it because the FIFO is always empty when we
> get a DISCONNECT message. Probably because every SG segment has a length
> that is a multiple of 128 bytes. (Juergen?)
>
> > +
> > + left = CURRENT_SC->transfersize - data_count;
>
> Are you sure about that? Perhaps you meant to write,
> left = scsi_bufflen(CURRENT_SC) - scsi_get_resid(CURRENT_SC);
>
> Is there a better name for this variable? Maybe 'sent' or 'bytes_sent'?
'left' can be renamed as 'done', and
done = GETSTCNT - (CURRENT_SC->SCp.ptr -
SG_ADDRESS(CURRENT_SC->SCp.buffer))
>
> > + for (i = 0; left > 0 && !sg_is_last(sg); i++, sg = sg_next(sg))
> > {
> > + if (left < sg->length)
> > + break;
> > + left -= sg->length;
> > + }
> > +
> > + if (data_count > 0) {
> > + CURRENT_SC->SCp.buffers_residual += i;
>
> Shouldn't that be,
> CURRENT_SC->SCp.buffers_residual = i;
Good catch.
>
> > + CURRENT_SC->SCp.buffer = sg;
> > +
> > + CURRENT_SC->SCp.ptr =
> > SG_ADDRESS(CURRENT_SC->SCp.buffer) + left;
> > + CURRENT_SC->SCp.this_residual =
> > CURRENT_SC->SCp.buffer->length -
> > + left;
> > + }
> > }
> >
> > SETPORT(SXFRCTL0, CH1|CLRCH1|CLRSTCNT);
> >
>
> BTW, datao_run() seems to guarantee that the FIFO will never contain more
> than min(128, SCp.this_residual) so I suspect that this code can be
> simplified. That's just BTW. I wouldn't attempt to optimize this branch as
> it will only run when the FIFO is not empty, if ever. So I'd prefer
> clarity. Besides, I don't have the hardware to test it on.
I'd suggest to simply translate into code which uses current sg helper.
Follows the fixed version, could you review again?
>From f03484d4bac083c39d70665cfbadb641093b63de Mon Sep 17 00:00:00 2001
From: Ming Lei <ming....@redhat.com>
Date: Wed, 12 Jun 2019 20:37:35 +0800
Subject: [PATCH] scsi: aha152x: use sg helper to operate scatterlist
Use the scatterlist iterators and remove direct indexing of the
scatterlist array.
This way allows us to pre-allocate one small scatterlist, which can be
chained with one runtime allocated scatterlist if the pre-allocated one
isn't enough for the whole request.
Signed-off-by: Ming Lei <ming....@redhat.com>
---
drivers/scsi/aha152x.c | 34 ++++++++++++++++++++--------------
1 file changed, 20 insertions(+), 14 deletions(-)
diff --git a/drivers/scsi/aha152x.c b/drivers/scsi/aha152x.c
index 97872838b983..7faecdefda56 100644
--- a/drivers/scsi/aha152x.c
+++ b/drivers/scsi/aha152x.c
@@ -2033,7 +2033,7 @@ static void datai_run(struct Scsi_Host *shpnt)
CURRENT_SC->SCp.buffers_residual > 0) {
/* advance to next buffer */
CURRENT_SC->SCp.buffers_residual--;
- CURRENT_SC->SCp.buffer++;
+ CURRENT_SC->SCp.buffer =
sg_next(CURRENT_SC->SCp.buffer);
CURRENT_SC->SCp.ptr =
SG_ADDRESS(CURRENT_SC->SCp.buffer);
CURRENT_SC->SCp.this_residual =
CURRENT_SC->SCp.buffer->length;
}
@@ -2139,7 +2139,7 @@ static void datao_run(struct Scsi_Host *shpnt)
if(CURRENT_SC->SCp.this_residual==0 &&
CURRENT_SC->SCp.buffers_residual>0) {
/* advance to next buffer */
CURRENT_SC->SCp.buffers_residual--;
- CURRENT_SC->SCp.buffer++;
+ CURRENT_SC->SCp.buffer =
sg_next(CURRENT_SC->SCp.buffer);
CURRENT_SC->SCp.ptr =
SG_ADDRESS(CURRENT_SC->SCp.buffer);
CURRENT_SC->SCp.this_residual =
CURRENT_SC->SCp.buffer->length;
}
@@ -2158,22 +2158,28 @@ static void datao_run(struct Scsi_Host *shpnt)
static void datao_end(struct Scsi_Host *shpnt)
{
if(TESTLO(DMASTAT, DFIFOEMP)) {
- int data_count = (DATA_LEN - scsi_get_resid(CURRENT_SC)) -
- GETSTCNT();
+ int done = GETSTCNT();
+ int data_count = (DATA_LEN - scsi_get_resid(CURRENT_SC)) - done;
+ struct scatterlist *sg = scsi_sglist(CURRENT_SC);
+ int i;
CMD_INC_RESID(CURRENT_SC, data_count);
- data_count -= CURRENT_SC->SCp.ptr -
- SG_ADDRESS(CURRENT_SC->SCp.buffer);
- while(data_count>0) {
- CURRENT_SC->SCp.buffer--;
- CURRENT_SC->SCp.buffers_residual++;
- data_count -= CURRENT_SC->SCp.buffer->length;
+ /*
+ * rewind where we have done, and we have to start from
+ * the beginning
+ */
+ for (i = 0; done > 0 && !sg_is_last(sg); i++, sg = sg_next(sg))
{
+ if (done < sg->length)
+ break;
+ done -= sg->length;
}
- CURRENT_SC->SCp.ptr = SG_ADDRESS(CURRENT_SC->SCp.buffer) -
- data_count;
- CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length +
- data_count;
+
+ CURRENT_SC->SCp.buffers_residual = i;
+ CURRENT_SC->SCp.buffer = sg;
+ CURRENT_SC->SCp.ptr = SG_ADDRESS(CURRENT_SC->SCp.buffer) + done;
+ CURRENT_SC->SCp.this_residual = CURRENT_SC->SCp.buffer->length -
+ done;
}
SETPORT(SXFRCTL0, CH1|CLRCH1|CLRSTCNT);
--
2.20.1
thanks,
Ming
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