From 6f4285d13300f1c8cd675a41ab390cea06173cd1 Mon Sep 17 00:00:00 2001 From: Pierre Ossman Date: Thu, 27 Sep 2007 10:48:29 +0200 Subject: sdio: adaptive interrupt polling The interrupt polling frequency is a compromise between power usage and interrupt latency. Unfortunately, it affects throughput rather severely for devices which require an interrupt for every chunk of data. By making the polling frequency adaptive, we get better throughput with those devices without sacficing too much power. Polling will quickly increase when there is an actual interrupt, and slowly fall back to the idle frequency when the interrupts stop coming. Signed-off-by: Pierre Ossman --- drivers/mmc/core/sdio_irq.c | 28 +++++++++++++++++++++++----- 1 file changed, 23 insertions(+), 5 deletions(-) (limited to 'drivers/mmc') diff --git a/drivers/mmc/core/sdio_irq.c b/drivers/mmc/core/sdio_irq.c index 8843a4c2fe91..f78ffeefed52 100644 --- a/drivers/mmc/core/sdio_irq.c +++ b/drivers/mmc/core/sdio_irq.c @@ -27,7 +27,7 @@ static int process_sdio_pending_irqs(struct mmc_card *card) { - int i, ret; + int i, ret, count; unsigned char pending; ret = mmc_io_rw_direct(card, 0, 0, SDIO_CCCR_INTx, 0, &pending); @@ -37,6 +37,7 @@ static int process_sdio_pending_irqs(struct mmc_card *card) return ret; } + count = 0; for (i = 1; i <= 7; i++) { if (pending & (1 << i)) { struct sdio_func *func = card->sdio_func[i - 1]; @@ -46,20 +47,21 @@ static int process_sdio_pending_irqs(struct mmc_card *card) sdio_func_id(func)); } else if (func->irq_handler) { func->irq_handler(func); + count++; } else printk(KERN_WARNING "%s: pending IRQ with no handler\n", sdio_func_id(func)); } } - return 0; + return count; } static int sdio_irq_thread(void *_host) { struct mmc_host *host = _host; struct sched_param param = { .sched_priority = 1 }; - unsigned long period; + unsigned long period, idle_period; int ret; sched_setscheduler(current, SCHED_FIFO, ¶m); @@ -70,8 +72,9 @@ static int sdio_irq_thread(void *_host) * asynchronous notification of pending SDIO card interrupts * hence we poll for them in that case. */ + idle_period = msecs_to_jiffies(10); period = (host->caps & MMC_CAP_SDIO_IRQ) ? - MAX_SCHEDULE_TIMEOUT : msecs_to_jiffies(10); + MAX_SCHEDULE_TIMEOUT : idle_period; pr_debug("%s: IRQ thread started (poll period = %lu jiffies)\n", mmc_hostname(host), period); @@ -101,9 +104,24 @@ static int sdio_irq_thread(void *_host) * errors. FIXME: determine if due to card removal and * possibly exit this thread if so. */ - if (ret) + if (ret < 0) ssleep(1); + /* + * Adaptive polling frequency based on the assumption + * that an interrupt will be closely followed by more. + * This has a substantial benefit for network devices. + */ + if (!(host->caps & MMC_CAP_SDIO_IRQ)) { + if (ret > 0) + period /= 2; + else { + period++; + if (period > idle_period) + period = idle_period; + } + } + set_task_state(current, TASK_INTERRUPTIBLE); if (host->caps & MMC_CAP_SDIO_IRQ) host->ops->enable_sdio_irq(host, 1); -- cgit v1.2.3