libertas: increase spi driver thread priority

Currently, the libertas main thread contends with the spi driver thread
in the TX path.  To improve throughput, ensure that the driver thread
has higher scheduling priority than the libertas main thread.  Do this
by making the libertas spi driver thread a low priority real time
thread.

We measured an average throughput improvement of 13%.

Signed-off-by: Anna Neal <anna@cozybit.com>
Signed-off-by: Andrey Yurovsky <andrey@cozybit.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --git a/drivers/net/wireless/libertas/if_spi.c b/drivers/net/wireless/libertas/if_spi.c
index 07311e71af926cad9d80156c700d4810b2cc713a..97493e2f4109105c3a2ed656b2c3c0f43d5147a0 100644 (file)
--- a/drivers/net/wireless/libertas/if_spi.c
+++ b/drivers/net/wireless/libertas/if_spi.c
@@ -1020,6 +1020,7 @@ static int __devinit if_spi_probe(struct spi_device *spi)
        struct libertas_spi_platform_data *pdata = spi->dev.platform_data;
        int err = 0;
        u32 scratch;
+       struct sched_param param = { .sched_priority = 1 };
 
        lbs_deb_enter(LBS_DEB_SPI);
 
@@ -1123,6 +1124,9 @@ static int __devinit if_spi_probe(struct spi_device *spi)
                lbs_pr_err("error creating SPI thread: err=%d\n", err);
                goto remove_card;
        }
+       if (sched_setscheduler(card->spi_thread, SCHED_FIFO, &param))
+               lbs_pr_err("Error setting scheduler, using default.\n");
+
        err = request_irq(spi->irq, if_spi_host_interrupt,
                        IRQF_TRIGGER_FALLING, "libertas_spi", card);
        if (err) {