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SubjectRe: drivers:soc:fsl:qbman:qman.c: Change a comment for an entry check inside drain_mr_fqrni function
On Fri, May 05, 2017 at 10:05:56AM +0200, Karim Eshapa wrote:
> Change the comment for an entry check inside function
> drain_mr_fqrni() with sleep for sufficient period
> of time instead of long time proccessor cycles.
>
> Signed-off-by: Karim Eshapa <karim.eshapa@gmail.com>
> ---
> drivers/soc/fsl/qbman/qman.c | 25 +++++++++++++------------
> 1 file changed, 13 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/soc/fsl/qbman/qman.c b/drivers/soc/fsl/qbman/qman.c
> index 18d391e..636a7d7 100644
> --- a/drivers/soc/fsl/qbman/qman.c
> +++ b/drivers/soc/fsl/qbman/qman.c
> @@ -1071,18 +1071,19 @@ static int drain_mr_fqrni(struct qm_portal *p)
> msg = qm_mr_current(p);
> if (!msg) {
> /*
> - * if MR was full and h/w had other FQRNI entries to produce, we
> - * need to allow it time to produce those entries once the
> - * existing entries are consumed. A worst-case situation
> - * (fully-loaded system) means h/w sequencers may have to do 3-4
> - * other things before servicing the portal's MR pump, each of
> - * which (if slow) may take ~50 qman cycles (which is ~200
> - * processor cycles). So rounding up and then multiplying this
> - * worst-case estimate by a factor of 10, just to be
> - * ultra-paranoid, goes as high as 10,000 cycles. NB, we consume
> - * one entry at a time, so h/w has an opportunity to produce new
> - * entries well before the ring has been fully consumed, so
> - * we're being *really* paranoid here.
> + * if MR was full and h/w had other FQRNI entries to
> + * produce, we need to allow it time to produce those
> + * entries once the existing entries are consumed.
> + * A worst-case situation (fully-loaded system) means
> + * h/w sequencers may have to do 3-4 other things
> + * before servicing the portal's MR pump, each of
> + * which (if slow) may take ~50 qman cycles
> + * (which is ~200 processor cycles). So sleep with
> + * 1 ms would be very efficient, after this period
> + * we can check if there is something produced.
> + * NB, we consume one entry at a time, so h/w has
> + * an opportunity to produce new entries well before
> + * the ring has been fully consumed.

Do you mean "sufficient" here rather than "efficient"? It's far less
inefficient than what the code was previously doing, but still...

Otherwise, looks good.

-Scott

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