soc/fsl/qbman: Add an argument to signal if NAPI processing is required.

dpaa_eth_napi_schedule() and caam_qi_napi_schedule() schedule NAPI if
invoked from:

 - Hard interrupt context
 - Any context which is not serving soft interrupts

Any context which is not serving soft interrupts includes hard interrupts
so the in_irq() check is redundant. caam_qi_napi_schedule() has a comment
about this:

        /*
         * In case of threaded ISR, for RT kernels in_irq() does not return
         * appropriate value, so use in_serving_softirq to distinguish between
         * softirq and irq contexts.
         */
         if (in_irq() || !in_serving_softirq())

This has nothing to do with RT. Even on a non RT kernel force threaded
interrupts run obviously in thread context and therefore in_irq() returns
false when invoked from the handler.

The extension of the in_irq() check with !in_serving_softirq() was there
when the drivers were added, but in the out of tree FSL BSP the original
condition was in_irq() which got extended due to failures on RT.

The usage of in_xxx() in drivers is phased out and Linus clearly requested
that code which changes behaviour depending on context should either be
separated or the context be conveyed in an argument passed by the caller,
which usually knows the context. Right he is, the above construct is
clearly showing why.

The following callchains have been analyzed to end up in
dpaa_eth_napi_schedule():

qman_p_poll_dqrr()
  __poll_portal_fast()
    fq->cb.dqrr()
       dpaa_eth_napi_schedule()

portal_isr()
  __poll_portal_fast()
    fq->cb.dqrr()
       dpaa_eth_napi_schedule()

Both need to schedule NAPI.
The crypto part has another code path leading up to this:
  kill_fq()
     empty_retired_fq()
       qman_p_poll_dqrr()
         __poll_portal_fast()
            fq->cb.dqrr()
               dpaa_eth_napi_schedule()

kill_fq() is called from task context and ends up scheduling NAPI, but
that's pointless and an unintended side effect of the !in_serving_softirq()
check.

The code path:
  caam_qi_poll() -> qman_p_poll_dqrr()

is invoked from NAPI and I *assume* from crypto's NAPI device and not
from qbman's NAPI device. I *guess* it is okay to skip scheduling NAPI
(because this is what happens now) but could be changed if it is wrong
due to `budget' handling.

Add an argument to __poll_portal_fast() which is true if NAPI needs to be
scheduled. This requires propagating the value to the caller including
`qman_cb_dqrr' typedef which is used by the dpaa and the crypto driver.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Aymen Sghaier <aymen.sghaier@nxp.com>
Cc: Herbert XS <herbert@gondor.apana.org.au>
Cc: Li Yang <leoyang.li@nxp.com>
Reviewed-by: Horia Geantă <horia.geanta@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Madalin Bucur <madalin.bucur@oss.nxp.com>
Tested-by: Camelia Groza <camelia.groza@nxp.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/include/soc/fsl/qman.h b/include/soc/fsl/qman.h
index 9f484113cfda..59eeba31c192 100644
--- a/include/soc/fsl/qman.h
+++ b/include/soc/fsl/qman.h
@@ -689,7 +689,8 @@ enum qman_cb_dqrr_result {
 };
 typedef enum qman_cb_dqrr_result (*qman_cb_dqrr)(struct qman_portal *qm,
 					struct qman_fq *fq,
-					const struct qm_dqrr_entry *dqrr);
+					const struct qm_dqrr_entry *dqrr,
+					bool sched_napi);
 
 /*
  * This callback type is used when handling ERNs, FQRNs and FQRLs via MR. They